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--- In ham_amplifiers@..., Bill Turner <dezrat@...>
wrote:

All of Jim's points are valid and a good amp designer will take

them

into account. I would just caution anyone on adding an arbitrary

XX%

of airflow "just in case". If you are serious about your amp

design,

you should test the seal temperatures under any and all operating
conditions it may run into such as high altitude, dirty air

filters,

high ambient temperature, etc, etc. Only then can you be sure your
design will work under those conditions.

My point was, and is, that measurements of airflow, back pressure,
etc, are nice but what counts in the end is the temperature of the
tube seals. That is the weak point and that is why tube

manufacturers

specify a maximum value. If a designer ONLY measures airflow and
ignores seal temp, he is asking for trouble down the road.

I realize for most of us homebrewers that isn't really practical to
perform all those tests in all cases, but we should try to come as
close as we can.

### Highly agreed. Seal temperature is the final determining
factor. Use of temperature sensitive paints are easy to use...
they are well documented in care and feeding and other
literature... they will melt and turn cystaline, when the pre-set
temp is exceeded. Due to the normal chimney setups... even my
Fluke mini 62 can't be pointed at the seals... only the portion of
the metal anode above the chimney.... which is nice to know.... but
not what we really want to know. On a glass tube... a Fluke 62
will work fine on the top seal. However,you still can't get at the
bottom pins/seals very easily.

Later... Jim VE7RF

Bill, W6WRT




------------ ORIGINAL MESSAGE ------------On Sun, 12 Nov 2006

13:21:24

-0000, "pentalab" <jim.thomson@...> wrote:

<snip>

### I wouldn't say that just because XXX amount of airflow
provides say 249 deg C.... that that is good enough. Eimac

bases

their airflow specs on 225 deg C.. allowing a 25 deg C "safety
factor". You also have to allow for dirty air filters,
partially clogged anode fins, etc. Most designers of

commercial

gear [ real broadcast gear... not Ameritron ham stuff] will take
the Eimac pressure requirements... and add 20% right off the

bat.

That will factor in ducting from blower to plenum... and also

dirty

air filters, right angle bends etc.

<snip>

--- In ham_amplifiers@..., "Robert B. Bonner"
<rbonner@...> wrote:

Garry,

That is a great question. I have a couple projects going together

RIGHT NOW that had me thinking the same thing.

It depends on if you cheat or not.

### huh ? AS long as you have a relay/contactor/ ckt breaker that
opens OFF BOTH sides of the 240v line... anything beyond that is
a moot point...and legal. BEWARE... if using fuses on the
primary.... they HAVE to be 240 V rated... NOT 120 V rated.
Here's why. IF only one fuse in one leg of the primary blew
open... and the 2nd fuse in the other leg was intact....you could
end up in a situation where 120 v is fed to one side of the plate
xfmr primary.... where it will simply pass throught the typ .08 ohm
dc resistance primary... then back to the OUTPUT side of the blown
fuse.[call this leg #2] Meanwhile... on the INPUT side of the
blown fuse.... you still have 120 V [coming from leg #1.] The
potential difference across the blown fuse in leg #1 will
be ...240 V. IE: with EITHER fuse blown [but only one], you
will have 240 v across an open fuse.... so DON'T use 120 V rated
fuses in either leg of a 240 v LINE.

### ALSO BEWARE.... some amps like the L4B... use two SEPARATE
circuit breaker's... one per hot leg... and NO tie bar between
em. These are usually the type that resemble a 3agc fuse
holder.When these type of breakers open up... they extend outwards.

OK what does that mean? 220V wiring is 2 wire plus ground, not 2

wire plus neutral.

### partially agreed. ALL wire now comes with a bare or
insulated grnd...whether u want it or not. The grnd is NEVER
considered any more in the wire count. So, you either
ask/order 2 conductor wire.... OR 3 conductor wire. 2 x
conductor wire comes with a grnd... so total wires = 3. 3 x
conductor wire also comes with a grnd... so total wires = 4. IE:
you ask fo 3 x wire XXX ga.... u get a total of 4 x conductor's.

If you use legal by code 220/221V (whatever it takes) building

practices you could get by with only 1 resistor in the step start.

#### The electrical code will state on a 240 v circuit you will
require a TWO pole breaker..and/or a TWO pole relay/contactor...
to open off BOTH sides of the line. After that.. they could care
less if u install a 12.5 ohm resistor in EACH hot leg... or a 25 ohm
resistor in just ONE hot leg. Putting a resistor in both legs is
a waste of effort. It's total LOOP resistance we are concerned
with here.

If you cheat and have some 110 volt circuitry in the amplifier

like a filament transformer that runs on 110 you would want to have
2 resistors in the step start.

### Agreed. BUT.... on an amp like the L4B.. and 99% of em...
that have a SEPARATE fil xfmr.... the fil xfmr will ALWAYS have
it's own dual 120 v primary's.... which can be wired in parallel
for 120v... or in series for 240 V. The only exception to
this.. would be if in a condo with 208/120V wiring per suite.
You can then run 208 V into the plate xfmr [wired for 240V.. so u
end up with slightly less plate V].... and run 120 V to the fil
xfmr [wired for 120V... so fil gets correct V]

### IF, indeed one had a fil xfmr that ONLY ran on 120v.... then,
you would have to ensure that the hot leg feeding the fil xfmr..
came from the SAME side of the 240 v line.... as your single
step start resistor.... so when step started... you step start BOTH
the HV supply AND the fil xfmr... at the same time...from the same
source.

In this situation you would have current flow on the GROUND LEAD.

### No you wouldn't. That could only happen if one side of the
120V fil xfmr [or any other 120 v device] was tied directly to
the chassis.. instead of the neutral. That isn't going to happen..
since it's not allowed... would violate every electrical code in
North America. On a similar note... you NEVER bond the neutral to
the chassis.... that also violates every electrical code in NA.
The ONLY thing bonded to the chassis is the grnd wire. With any
shorts from either side of line to chassis... the grnd wire
handles the full fault current.

### On circuits which require a huge 240 V load... like a HV
supply.... but only a tiny load for the 120 V load... like say a
120 V blower... some tiny xfmr's for a T/R supply, etc... then
it would be ok to use a smaller neutral.... as long as the neutral
could handle the entire fault current... IF a line to neutral
short occured. EG: 2 ga wire for each hot leg... and a 100 A
main breaker in panel... but only 6 ga wire for the neutral....
and also 6 ga wire for the grnd.

That's why professional grade equipment has a 220 - 110 step down
transformer on board.

### You see that in the Henry 8 k manual. They do that to run
the 120 v Dayton blower. In EU/UK... they don't use a 3 wire 220
v line. They only have 2 x wires from the pole pig... with 220 v
across em. One side of the line is bonded to earth ground... so
one leg is hot... the other leg is valled neutral. That way, they
only have to fuse the ONE hot leg... and any switches, relays,
etc, are only required to be single pole types... for the one hot
leg. As per the 8K... when you look up the Dayton blower part
number they spec in their parts list in their manual.... and cross
reference it to the Dayton blowers on Grainger's website... turns
out it's the 230 V version of the same blower... and in fact, the
240/120 V step down xfmr shown in the schematic and also the picture
drawings.... doesn't exist.

## Notice on 240 V clothes dryers... they always include a
neutral... to run the 120 V blower. Seems stupid to me. They
shoulda just used a 240v blower... and could have eliminated the
requirement for a neutral..... just like a 240 v hot water
tank.... none of which have a neutral... since the heating els run
on 240 V only.




Another option is 4 wire circuitry where you have 220

plus neutral and ground. What a pain with the outlets etc...

### what's the problem with the outlets ??? A 30 A dryer
outlet comes with 2 x hots, one neutral... one gound. A 40 A
stove is exactly the same thing. Ditto with 20 A circuits.

A guy should follow good construction practices. BUT for home

brewing does it really matter? NAW it will turn on and work.

### with HB HV supplies... you don't need an outlet. You just
hardwire the 2 ga wire directly to the line side input of the
front or rear panel mounted breaker. OR hardwire the 2 ga wire
directly to the jumbo contactor input..... either way... you still
have the breaker in the main panel that feeds this mess. You can
buy 75/100/150/200 A outlets... cost a small fortune. You don't
need em.... just hardwire the big wire in..... and when working on
the amp.... kill the breaker in the main panel. IF the HV
supply/amp needs to be rolled over to the bench... just
disconnect the 4x wires at the HV/amp end.

Just an FYI, I use a double resistor. It just happens to look

prettier, double pole relay, pair of resistors, double pole relay
all in line. Nice pretty yellow adjustable time delay relay.

### Here's what I do. I use 25 ohms in one leg only... and only
one contactor to short out the resistor. The kicker is.. I use a
pair of paralled 50 ohm resistor's to make up the 25 ohms ! If
one resistor ever opened up... the 2nd one [albeit 50 ohms] is
still in the circiut. That way... I can never shunt an open single
resistor with the step start contactor... and slam a huge load on
the diodes.... IE: no step start at all... which would be a
disaster with 100-200 uf C input filter. These large metal
finned resistor's you see made by DALE and other's, works
perfectly for the step start R. Just bolt it to metal chassis
anywhere. Cuz of our magnetizing current.... I use a min of a 100w -
200 W rated units... EACH. You will have the entire 240 V
dumped across em when you 1st hit the switch. When everything
settles down... I still have 2 A of magnetizing current flowing
through em..[100/200 w]... then they get shunted.

## I also use the yellow /white adjustable Time delay relay. The
TD relays are all DPDT 10 A contacts.... which are used to
activate the coil of the step start contactor. The big step
start contactor has loads of AUX contacts... which are wired to
the amp key line.... ditto with main incoming contactor.... so
you can't key the amp unless all the contactor's are actually
operated. We use loads of 120 v neons as well.. status lamps...
to tell us instantly, where a problem is.. works slick.. if and when
it comes time to trbl shoot anything. A row of 3agc fuses [and
more neons on the output sides of the fuses] are the various feeds
for the blower, TD relays, small xfmr's for T/R relays, contactor's
etc.

### On the big stuff.... we use a separate Time delay for the fil
xfmr... which has it's own step start resistor/ variac, etc. The
fil TD is set for 8-10 seconds.... the HV delay is set for 15-
25 seconds. The blower over run TD is set for 15 mins.

-also have an airflow vane/ switch, retrofitted inside the blower.
Contacts of the airflow switch are wired to the coil of a small
relay.... whose contacts open off the 240 V to the fil xfmr.
The last thing you want is no air to a tube... esp when it's 30'
away... in another room. The slick thing about this setup is...
IF the commercial AC power goes off.... everything shuts down.
When the power comes back on.... everything just goes through it's
normal step start sequence etc. You can't key the amp... until
it's all finished.

Later... Jim VE7RF

BOB DD

-----Original Message-----
From: ham_amplifiers@...

[mailto:ham_amplifiers@...]

On Behalf Of Garry Drummond
Sent: Sunday, November 12, 2006 9:29 AM
To: ham_amplifiers@...
Subject: [ham_amplifiers] Inrush filament current protection

When running an amp on 240 volts, is it necessary to put a

resistor in

both sides of the 240 volt line for inrush current protection or

would a

single resistor of adequate size in one leg do the job? I am

speaking of

the typical amplifier running a pair of 3-500's.

Thanks,
Garry - WR4R



Yahoo! Groups Links

For the life of me, I can't figure out why you would need one for
each line lead? If the voltage drops, the current rises making the
same output power from the transformer. The same amount of power will
be drawn either way if the amps output is the same. Example, 220Vac x
14 amperes is 3,080 watts, and 110 Vac x 28 amperes is 3,080 watts. A
25 ohm resistor at 110 Vac or 220 Vac would see the same power in
watts since when the voltage drops, the current rises, and when
voltage rises to 220 vac, current drops by 1/2. Does the surge
current increase more than double by dropping the voltage down to 110
Vac? The only difference in the primary windings are having them
either in series or parallel.

Thanks,

Will

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Nov 12, 2006, at 7:29 AM, Garry Drummond wrote:

When running an amp on 240 volts, is it necessary to put a

resistor in

both sides of the 240 volt line for inrush current protection or
would a
single resistor of adequate size in one leg do the job? I am
speaking of
the typical amplifier running a pair of 3-500's.

Amplifiers that run on two voltages need two step-start resistors,
but those that run on one V need only one

Thanks,
Garry - WR4R

R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

Jim,

I've seen these used, but they were used in smaller DC supplies. I
have several books on the subject and will look it up. That value
though seems way to much at 35 uF for this. Placed across the primary
leads, it will start looking like a short or a leak if big enough.
That's why your seeing an increased current. The cap is causing more
current to be drawn or mag I + cap I. All transformers have
magnetizing current which is low compared to their output power.
However, the larger the transformer, the more this will be. Also, the
higher the flux density its ran at, the higher it will be. For this
type transformer service, the power factor should be about 0.95 or
so. If the ripple is low where you want it, I wouldn't worry about
adding anything else that may draw more current.

Best,

Will


--- In ham_amplifiers@..., "pentalab" <jim.thomson@...>
wrote:

Gents

My buddy tried this... said it worked. He gave me a 32 uf cap

to

try it myself. It gets installed directly in parallel with the
pri of the plate xfmr. [this is for a C input HV supply].

I didn't see any improvement... but I may well have easily had the
wrong value. What I did notice was the magnetizing current went
up on the pole pig... from 1.8A to 2.3A ! The magnetizing
current is why the step start never allows you to charge the caps

up

to max V. [u always have current flowing through the drop resistor]
The plate xfmr is always sucking magnetizing current... even with
nothing connected to the secondary.

Dahl himself said the concept won't work. Seems to me it
would work on TX... and be the wrong value cap on RX... because

of

load. The idea I had was to use a small possibly sped up vac
relay... tied into the T/R set up... to open/close... one leg of

the

cap.

I also noticed that the new 253 lb Dahl draws only 1.6 A of
magnetizing current. I thought it would be double that of the
smaller 120 lb pole pig.... it's not. The smaller pole pig draws
1.8 A. My electrician buddy sez they never oversize vault
transformers... the idea being you don't want to be drawing excess
magnetizing current.

I take it the magnetizing current is in addition to the normal
load ??

If my electrician buddy is correct... then why does the bigger
Dahl draw LESS magnetizing current than the smaller 120 lb pole
pig ??

1.6 A is nothing to sneeze at... = 384 Va. 2.3 A = 552 Va

Magnetizing current is one thing.... power factor is another.

These

xfmr's typ have a .9 pwr factor... and even worse with a bigger HV
C input filter. Maybe I'm confused here... but it appears the

load

is not the XL load of the xfmr... but the HV C filter on the sec
side ?

Power factor correction caps work great on motor's and probably
xfmr's.. depending on the type of filter used.. C or resonant
choke.

Who's the expert on this ? Maybe Dahl is right.. and it might

be

fruitless....... or maybe it works on TX... but correction cap has
to be switched out on RX. IF it works... how do you go about
sizing the correction cap ?.... and how much current flows through
the correction cap ???

Later... Jim VE7RF

Hirams Percys father, Hiram Stevens Maxim was the daddy of the Maxim
machine gun that helped cause all the carnage in WWI. Though the
Browning machine gun eventually won out during US government testing,
the Maxim was still used in Britan. It went out of production though
and became the Vickers machine gun. The size came down and others had
increased capacity like the Thompson "Tommy" gun. This was the mobs
favorite in the 20's. The same Browning 30 and 50 cal's are still
being produced and used today. The Vickers was used up to 1968 by
Britan.

I would think that dealing out death ran in the Maxim family. The
first way was quickly, and the second silently.

Hiram Stephens brother Hudson Maxim was also a military inventor,
specializing in explosives. Again, a death dealer.

Just because Hiram Percy was one of the founders of the ARRL, doesn't
hide his family history.

Best,

Will

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Nov 12, 2006, at 3:48 AM, pentalab wrote:

--- In ham_amplifiers@...,

RICH SEZ... opposite page (p.9) there's a picture of the inventor

of

the firearms silencer, Hiram P. Maxim, wearing a set of

headphones -

but strangely he is given no credit whatsoever for his brilliant
invention.

#### Hiram Percy Maxim DIDN'T invent the silencer.... his FATHER
did.

Not according to history, Jim.

..per "200 metres and down". His father was on this noise
abatement program.... and came up with ways to quieten down

everything

from air conditioners to cars.. planes etc. He didn't like the way
the noise level was rising in the cities. His next step was guns.
His 1st silencer was for shot guns... sort of like an acoustical
mechanical notch filter. They had to know how many grains the
projectiles were.. the freq, velocity, etc. The 1st shot gun
silencers sold for just $7.00 . Organized crime types apparently
wanted em real bad. Wonder how many people got knocked off from

his

invention?

"Hiram Percy Maxim
born Sept. 2, 1869, Brooklyn, N.Y., U.S.
died Feb. 17, 1936, La Junta, Colo.
American inventor and manufacturer known especially for the

"Maxim

silencer" gun attachment. Son and nephew of famous inventors,

Maxim

graduated from Massachusetts Institute of Technology, then in

Boston,

at age 16 ..."

The thing that some people don't realize about silencers is that

they

do not silence the sonic crack of a bullet traveling faster than

the

speed of sound (c. 1060 feet per second), so even a 22-LONG RIFLE
equipped with a silencer still makes a lot of racket. Also, Maxim-
silencers are useless on any revolver since a stentorian blast

exits

out the side from the gap between the receiver and the cylinder.
Thus, in "The Godfather" series, Vito Corleone expertly wraps a

towel

around the revolver to muffle the cylinder gap noise as well as

the

muzzle-blast when he terminates the neighborhood asshole.

Shotgun silencers would be more like mufflers because the

pellets

typically leave the barrel about 300-ft-sec above the speed of

sound.

### Here's a question. Can one still be an ARRL life member ??

The last I heard, yes.

As
in.... pay XXX dollars. Im talking about today....now.

### My buddy is an ARRL lifer. I'm sure it cost him something
bizzare like a few hundred bucks... back in 1976. Thought it was

like

$500.00 to $750.00

Later.... Jim VE7RF

R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

On Nov 12, 2006, at 7:29 AM, Garry Drummond wrote:

When running an amp on 240 volts, is it necessary to put a resistor in
both sides of the 240 volt line for inrush current protection or would a
single resistor of adequate size in one leg do the job? I am speaking of
the typical amplifier running a pair of 3-500's.

Amplifiers that run on two voltages need two step-start resistors, but those that run on one V need only one

Thanks,
Garry - WR4R

R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

Garry,

That is a great question. I have a couple projects going together RIGHT NOW
that had me thinking the same thing.

It depends on if you cheat or not.

OK what does that mean? 220V wiring is 2 wire plus ground, not 2 wire plus
neutral.

If you use legal by code 220/221V (whatever it takes) building practices you
could get by with only 1 resistor in the step start.

If you cheat and have some 110 volt circuitry in the amplifier like a
filament transformer that runs on 110 you would want to have 2 resistors in
the step start.

In this situation you would have current flow on the GROUND LEAD.

That's why professional grade equipment has a 220 - 110 step down
transformer on board. Another option is 4 wire circuitry where you have 220
plus neutral and ground. What a pain with the outlets etc...

A guy should follow good construction practices. BUT for home brewing does
it really matter? NAW it will turn on and work.

Just an FYI, I use a double resistor. It just happens to look prettier,
double pole relay, pair of resistors, double pole relay all in line. Nice
pretty yellow adjustable time delay relay.

BOB DD

When running an amp on 240 volts, is it necessary to put a resistor in both sides of the 240 volt line for inrush current protection or would a single resistor of adequate size in one leg do the job? I am speaking of the typical amplifier running a pair of 3-500's.

Thanks,
Garry - WR4R

All of Jim's points are valid and a good amp designer will take them
into account. I would just caution anyone on adding an arbitrary XX%
of airflow "just in case". If you are serious about your amp design,
you should test the seal temperatures under any and all operating
conditions it may run into such as high altitude, dirty air filters,
high ambient temperature, etc, etc. Only then can you be sure your
design will work under those conditions.

My point was, and is, that measurements of airflow, back pressure,
etc, are nice but what counts in the end is the temperature of the
tube seals. That is the weak point and that is why tube manufacturers
specify a maximum value. If a designer ONLY measures airflow and
ignores seal temp, he is asking for trouble down the road.

I realize for most of us homebrewers that isn't really practical to
perform all those tests in all cases, but we should try to come as
close as we can.

Bill, W6WRT




------------ ORIGINAL MESSAGE ------------On Sun, 12 Nov 2006 13:21:24
-0000, "pentalab" <jim.thomson@...> wrote:

<snip>

### I wouldn't say that just because XXX amount of airflow
provides say 249 deg C.... that that is good enough. Eimac bases
their airflow specs on 225 deg C.. allowing a 25 deg C "safety
factor". You also have to allow for dirty air filters,
partially clogged anode fins, etc. Most designers of commercial
gear [ real broadcast gear... not Ameritron ham stuff] will take
the Eimac pressure requirements... and add 20% right off the bat.
That will factor in ducting from blower to plenum... and also dirty
air filters, right angle bends etc.

<snip>

Gents

My buddy tried this... said it worked. He gave me a 32 uf cap to
try it myself. It gets installed directly in parallel with the
pri of the plate xfmr. [this is for a C input HV supply].

I didn't see any improvement... but I may well have easily had the
wrong value. What I did notice was the magnetizing current went
up on the pole pig... from 1.8A to 2.3A ! The magnetizing
current is why the step start never allows you to charge the caps up
to max V. [u always have current flowing through the drop resistor]
The plate xfmr is always sucking magnetizing current... even with
nothing connected to the secondary.

Dahl himself said the concept won't work. Seems to me it
would work on TX... and be the wrong value cap on RX... because of
load. The idea I had was to use a small possibly sped up vac
relay... tied into the T/R set up... to open/close... one leg of the
cap.

I also noticed that the new 253 lb Dahl draws only 1.6 A of
magnetizing current. I thought it would be double that of the
smaller 120 lb pole pig.... it's not. The smaller pole pig draws
1.8 A. My electrician buddy sez they never oversize vault
transformers... the idea being you don't want to be drawing excess
magnetizing current.

I take it the magnetizing current is in addition to the normal
load ??

If my electrician buddy is correct... then why does the bigger
Dahl draw LESS magnetizing current than the smaller 120 lb pole
pig ??

1.6 A is nothing to sneeze at... = 384 Va. 2.3 A = 552 Va

Magnetizing current is one thing.... power factor is another. These
xfmr's typ have a .9 pwr factor... and even worse with a bigger HV
C input filter. Maybe I'm confused here... but it appears the load
is not the XL load of the xfmr... but the HV C filter on the sec
side ?

Power factor correction caps work great on motor's and probably
xfmr's.. depending on the type of filter used.. C or resonant
choke.

Who's the expert on this ? Maybe Dahl is right.. and it might be
fruitless....... or maybe it works on TX... but correction cap has
to be switched out on RX. IF it works... how do you go about
sizing the correction cap ?.... and how much current flows through
the correction cap ???

Later... Jim VE7RF

On Nov 12, 2006, at 3:05 AM, pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Nov 11, 2006, at 10:54 AM, Robert B. Bonner wrote:

Well I do have responses for the comments.

I do currently own a 3K-A. Have had virtually all of them in the

past.

Also have owned an L4B, Swan Mark II never SB-220 or TL-922

however

I've
worked on almost everything at one time or another.

The problem with Henry's and Heath's design is the SOCKETS. The
Johnson
socket mounted below the chassis on 4 bent metal brackets is

the

problem.

### Drake uses the same Johnson sub mounted sockets on the L4B.
[came out in 1969].. on aluminium cylinder standoffs. The 3-500Z
spec is for only .08" h2o... which is easy to achieve. That's
zip..pressure wise. Drake used real Eimac SK-410's on the older
plane jane L4 [1964]

The little holes in the Johnson socket were matched to the 4-XX
series of
tubes. 4-65, 4-125, 4-250 and were designed before they

developed

tubes the
size of 4-400, 3-400, 3-500. There is inadequate cooling around

the

bases
when using these sockets with the larger tubes.

I've seen Eimac 3-500's with the letters burned off one side in
amps like
the SB-220.

RICH SEZ...I have never seen an amplifier with a cooling system

like a SB-220's.

#### Sure their is. The Ten tec Centurion uses the same deal.
The chassis is raised UP, right where the sockets are. Resembles a
small box sitting on the chassis... with two[oposing] sides chopped
out.. so air can pass UNDERNEATH...and hit all the pins. The tiny
slots in the cab are where they screwed up... really restricts air
getting in and out.

... but the Heath SB-220 does not do this.

The correct Eimac air system sockets REALLY move air through

them

in all the
right places. For instance the 410's and 510's have a collar

where you

actually hook up ducted air to the base.

### agreed. A 4-1000 Deck I bought from W6RU back in 1977 was
done exactly like that. Blower mounted below... with flexible
ducting that fit that collar like a glove.

## On HB 4-1000's... I carefully removed the pins from the SK-
510 socket... then sliced off that collar with a hacksaw... re-
asembled.. then installed em. In that case... blower was on rear
apron... pressurized the chassis.

The problem is that the 3-500Z air system socket requires a high-
pressure centrifugal blower, and Ham amps used an ordinary
centrifugal blower.

### See my note above. A 3-500Z only requires a .08" h2o pressure.

Correct, but Eimac's 0.82" water column spec is the pressure differential across the socket, and that usually means a fairly noisy blower.

... In this case.. the grilles are used to keep
fingers away from the anodes... yet let air pass freely... plus
they look good.

RICH SEZ... That's how I do it. I also use a varnished cardboard

flap that hinges up to let the air out. It just doesn't look as
pretty.

### It would look like hell! Now that's what I call "K-mart
construction". Rich would call it part of his.. "ugly amplifier"
scene.

A square of varnished cardboard with two nickels glued to the corners along one edge is light enough to rise automatically with the airflow passing through an 8170. When the amp is off the cardboard flops down, keeping spiders from constructing webs on the insides.

### somebody.. think it was W7RF, radio dan.. supplied curved
plexiglass covers for the henry amps.. to make the exhaust air do
a sweeping right angle... facing the back... this was supposed to
kill some noise.... it would stop dust from settling in.. when not
in use.

A Heath cover is a piece of junk. They paint more of the hole area
closed than have open...

### agreed. Both Heath and Drake woulda been better off to just
made the entire top and sides solid... and 2 x big diam holes..
with fan grilles... right above the tubes.

Heath's SB-220 blows cooling air horizontally and out the left side of the perforated cabinet. Holes above the tubes would do nothing.

### here's the interesting bit. Eimac states the glass tubes
cool by infared radiation.... well my natural gas fireplace puts
out loads of radiant heat.... a 3-500Z doesn't.

So objects that glow red-orange do not exhibit infra-red radiation?

...

R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

--- In ham_amplifiers@..., Bill Turner <dezrat@...>
wrote:

The only absolutely guaranteed measure of correct airflow is to
measure the temperature of the tube seals as specified by the tube
manufacturer, under full load for long enough for the tube to reach
max temp at that load. Any airflow beyond that is not necessary but
may give one peace of mind.

Bill, W6WRT

#### Well.. Eimac specs ceramic metal tubes for a seal temp of
250 deg C [482 deg F] On a triode... this is where the lower
portion of the anode just touches the ceramic "stem". The top part
of the anode can be much hotter. The issue is the seal temp on
the stem. The other concern is the seal temp where the fil
connection is located.

### I wouldn't say that just because XXX amount of airflow
provides say 249 deg C.... that that is good enough. Eimac bases
their airflow specs on 225 deg C.. allowing a 25 deg C "safety
factor". You also have to allow for dirty air filters,
partially clogged anode fins, etc. Most designers of commercial
gear [ real broadcast gear... not Ameritron ham stuff] will take
the Eimac pressure requirements... and add 20% right off the bat.
That will factor in ducting from blower to plenum... and also dirty
air filters, right angle bends etc.

### Then they have to allow for variations in inlet air temp. Very
few will use Air conditioning to cool inlet air on a hot day.
Then you have to factor in elevation. At 5000' you need 20+% more
air... and also 20+% more pressure. Then the last kicker is...
you have to procure a blower. Now blowers are rated at SEA level
only..... so one has to go through the various formulae
for "blowers for elevated locations".... to find a sea level rated
blower... that when de-rated.. will work at elevation.

### The tubes need XXX LBS of air per minute.... called mass
volumetic airflow rate. The higher you go... the thinner the
air... hence the MORE of it you need CFM wise... just to get the
same WEIGHT of air per minute.

### Now having said all that... hams are always worried about
noise... the real commercial stuff and engineer's who design it...
could care less about noise. Apparently on the AL1200-1500...
they all come with a 4 x speed blower. That should handle
everything from hardcore RTTY ops to casual ssb ops.... and also
handle seasonal variations from winter to summer.

### Broadcaster's have an entirely different scenario to deal with.
They don't RX... so local noise level is not an issue. They don't
qsy... so are stuck on one freq... only have one ant array to worry
about. The swr is always flat. It's called simplex. TX... NO
RX. Also no T/R relays to mess with, etc.

### personally, I wouldn't run any metal tube with a seal temp of
225 deg C... even if Eimac sez that's ok. That doesn't allow any
wiggle room when stuff goes wrong... like off resonance for hrs on
end....... or having enough air for ssb... but not enough for FM.
I like Robert Bonner's idea.... use a variac.. or other motor speed
control... and dial it up/down as needed. Some other scheme's I
have used are a resistor in one leg of blower.... and shorted out on
TX... so it's part of the T/R relay scheme. You don't need all the
air on RX.

Later... Jim VE7RF

------------ ORIGINAL MESSAGE ------------

On Sat, 11 Nov 2006 12:26:27 -0300, GGLL <nagato@...> wrote:

how do one determine correct airflow?.

On Nov 12, 2006, at 3:48 AM, pentalab wrote:

--- In ham_amplifiers@...,

RICH SEZ... opposite page (p.9) there's a picture of the inventor of
the firearms silencer, Hiram P. Maxim, wearing a set of headphones -
but strangely he is given no credit whatsoever for his brilliant
invention.

#### Hiram Percy Maxim DIDN'T invent the silencer.... his FATHER
did.

Not according to history, Jim.

..per "200 metres and down". His father was on this noise
abatement program.... and came up with ways to quieten down everything
from air conditioners to cars.. planes etc. He didn't like the way
the noise level was rising in the cities. His next step was guns.
His 1st silencer was for shot guns... sort of like an acoustical
mechanical notch filter. They had to know how many grains the
projectiles were.. the freq, velocity, etc. The 1st shot gun
silencers sold for just $7.00 . Organized crime types apparently
wanted em real bad. Wonder how many people got knocked off from his
invention?

"Hiram Percy Maxim
born Sept. 2, 1869, Brooklyn, N.Y., U.S.
died Feb. 17, 1936, La Junta, Colo.
American inventor and manufacturer known especially for the “Maxim
silencer” gun attachment. Son and nephew of famous inventors, Maxim
graduated from Massachusetts Institute of Technology, then in Boston,
at age 16 ..."

The thing that some people don't realize about silencers is that they
do not silence the sonic crack of a bullet traveling faster than the
speed of sound (c. 1060 feet per second), so even a 22-LONG RIFLE
equipped with a silencer still makes a lot of racket. Also, Maxim-
silencers are useless on any revolver since a stentorian blast exits
out the side from the gap between the receiver and the cylinder.
Thus, in "The Godfather" series, Vito Corleone expertly wraps a towel
around the revolver to muffle the cylinder gap noise as well as the
muzzle-blast when he terminates the neighborhood asshole.

Shotgun silencers would be more like mufflers because the pellets
typically leave the barrel about 300-ft-sec above the speed of sound.

### Here's a question. Can one still be an ARRL life member ??

The last I heard, yes.

As
in.... pay XXX dollars. Im talking about today....now.

### My buddy is an ARRL lifer. I'm sure it cost him something
bizzare like a few hundred bucks... back in 1976. Thought it was like
$500.00 to $750.00

Later.... Jim VE7RF

R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

On Nov 11, 2006, at 7:20 PM, Bill Turner wrote:

The only absolutely guaranteed measure of correct airflow is to
measure the temperature of the tube seals as specified by the tube
manufacturer, under full load for long enough for the tube to reach
max temp at that load. Any airflow beyond that is not necessary but
may give one peace of mind.

... provided that if the tube blows out of the socket, the operator can catch it on the fly.

Bill, W6WRT

------------ ORIGINAL MESSAGE ------------

On Sat, 11 Nov 2006 12:26:27 -0300, GGLL <nagato@...> wrote:

how do one determine correct airflow?.

R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

--- In ham_amplifiers@...,

RICH SEZ... opposite page (p.9) there's a picture of the inventor of
the firearms silencer, Hiram P. Maxim, wearing a set of headphones -
but strangely he is given no credit whatsoever for his brilliant
invention.

#### Hiram Percy Maxim DIDN'T invent the silencer.... his FATHER
did. ..per "200 metres and down". His father was on this noise
abatement program.... and came up with ways to quieten down everything
from air conditioners to cars.. planes etc. He didn't like the way
the noise level was rising in the cities. His next step was guns.
His 1st silencer was for shot guns... sort of like an acoustical
mechanical notch filter. They had to know how many grains the
projectiles were.. the freq, velocity, etc. The 1st shot gun
silencers sold for just $7.00 . Organized crime types apparently
wanted em real bad. Wonder how many people got knocked off from his
invention?

### Here's a question. Can one still be an ARRL life member ?? As
in.... pay XXX dollars. Im talking about today....now.

### My buddy is an ARRL lifer. I'm sure it cost him something
bizzare like a few hundred bucks... back in 1976. Thought it was like
$500.00 to $750.00

Later.... Jim VE7RF

On Nov 11, 2006, at 3:42 PM, Tony King - W4ZT wrote:

Rich wrote:

On Nov 10, 2006, at 5:46 AM, Tony King - W4ZT wrote:

<snip>

But quitting doesn't help... without a strong lobby, we have no

voice

for ham radio.

Mexican Hams have no such voice and they can operate any mode they
choose on any Ham band. We have the ARRL and we can't.

I agree with that... most countries do not have the spectrum grab that
goes on here in this country either. That's one factor for having a
voice in the process. From having sat in meetings at the FCC on UWB
issues with not only folks from ARRL but folks from the cell phone
companies, airlines and other interested parties, it certainly helps to
have a lobby... even if people like Michael Powell wasn't briefed and
didn't care about what we were there to discuss.

Personal and group lobbying for change at ARRL may be
time better spent. Start with your friends, get to know your

Section

Manager and District Director.

The problem with the Directors is that the League effectively
controls them with "shaking hands money". Another questionable area
is vote counting.

I don't know about those issues personally but if that is going on, then
that's a change that needs taken care of.

How would the membership go about doing it? According to a friend who worked at HQ, the powers that be joke about the membership thinking that it controls the Directors.

Enough people sending the message will
get it pushed up to the top.

I don't think the hierarchy listens to peons like me, Tony. For
example, the church with the pedophile priest problem: The first
case to receive national press coverage was in Louisiana in 1985 --
but the hierarchy did virtually nothing. In January 2002, the
scandal really hit the fan, and again the hierarchy did virtually
nothing. Of late, lay members who see contributing monies to defend
such priests as a waste of their money have stopped contributing. My
guess is that money talks loudest with the powers that be.

I know it does at the FCC... but at the ARRL? I am not sure what that is
going to buy.

Money puts food on the table and makes the mortgage payment.

Regarding the other issue... the affected churches must
deal with their own problems... I personally think it is a shame and a
crime and folks that bugger little kids deserve to die.

For c. 10% of priests, the problem is that they were altar-boys who experienced the same situation and ended up making it an unseen tradition. When the vow of chastity became mandatory in the 12th century, Pete Comestore wrote:

"The devil never harmed the church so much as when the church herself adopted the vow of celibacy."

It HAS to be
more costly to produce QEX as opposed to including the

articles in

QST.
Seems to me they're boiling QST down and what's left isn't the

best

part... some of the recent articles sure make that obvious.

When I

was a
beginner there were plenty of articles WAY over my head in QST.

This was also my experience in high-school, Tony, but after a few
years of additional schooling this changed and I realized that:
1. Designing and building RF transmitting amplifiers isn't akin to
rocket science.

It wasn't all about RF amplifiers back then... there were lots of
construction and technical articles.

RF-amplifiers, UHF, and regulated power supplies were some my main
areas of interest.

That's good... my point was, there were lots of articles on different
subjects. At least there wasn't the technical void there is today
because someone decided to siphon off the technical expertise to some
other magazine in an effort to make more money.

Exactly, and nobody likes to get fleeced.

Obviously I do NOT
subscribe to QEX. I've expressed my displeasure about the dumbing down
of QST but I haven't seen a response to that ;)

My guess is that the League is like the organization in Italy that hates like hell to admit to mistakes.

2. Many of the articles in QST were difficult to fathom because

the

author did a somewhat less than ok job of explaining what was

going

on so that new guys could understand.

Well, there is always a percentage like that but looking back at
many of
them, they were good.

Lack of explanation is not good because those who already know the
subject are not the ones most interested in reading an article, so
the article needs to be written so as not to lose those who want to
acquire the knowledge that the author acquired from the project at
hand. The word that describes this type of writing is "Readable".
I try to write readable stuff. If what I write is boring to experts,
I could not care less, the readers I hate to lose are those who
aren't experts.

And that's a very good point. I'd much rather have a solid base of folks
that weren't experts but were really interested than a few experts that
weren't interested in teaching the new folks anything. I appreciate your
efforts!

Thank you.

Of course they didn't see some things the same
way we do now... different view on technology or things learned

during

the last 50 years... but many were an honest effort to do a good

job.

Rich, you've spent a lot of your time trying to do a good job on
articles for QST so they're not ALL bad ;)

I made up my mind about the way articles should be written when I

was a

Sophomore in high-school and my parents gave me a subscription to

QST

for Xmas.

That's good. I'm not a good writer but I can appreciate things that are
written well and it's easy to see, after a lot of years, through those
that aren't.

...

One day when I was bicycling home from Jr. High School, I stopped
by the C-Street Market and I bought a 1955 Radio Amateur's Handbook.
On page 8 I read that we owe our amateur radio to the American Radio
Relay League. This strikes me as a bit odd. How about you?

The thought of it makes me puke... that was real stupid back then. I'm
glad it got changed.

On the opposite page (p.9) there's a picture of the inventor of

the firearms

silencer, Hiram P. Maxim, wearing a set of headphones - but

strangely

he is given no credit whatsoever for his brilliant invention.

Not surprised... considering a lot of them were/are gun grabbers and
such anyhow.

Hiram invented the silencer because his dad invented the machine-gun, and the damn things make too much noise.

HPM deserved credit for a lot of things but since the rag
was dedicated to ham radio, they didn't bother to acknowledge his other
achievements. That's too bad. There should have been and still SHOULD be
a short history lesson there so folks knew he was more than just a radio
geek.

I also find it disturbing that the ARRL tries to control the

way we use

amateur radio bands. Take a look at the 1.8MHz band: There are no
ARRL-approved sub-bands. No part of the band is reserved for

CW, for

AM, for spark. for SSB, for snobs, or for any we're better than

you

are elite group. We run what mode we want in any clear space we
want. Things pretty much sort themselves out, and nobody owns a
certain frequency -- with that one exception, of course.

True... even the new rules creating much larger phone segments

on 75/80

wont help some of that. 75 meters is terrible these days with

some of

the most inconsiderate, meowing, singing, trash mouth crap I

have ever

heard. Does not spreading manure around help to dispel the smell?

No, from personal experience ;) it actually increases the smell for a
time... but in the case of the bands, it probably will improve some
things though some of us will have to move away from the established
groups that have driven their stake deep into the core and will never move.

Good riddance methinks.

I have mixed feelings about total mixed use on the bands. You're right
that other countries don't have segmented bands like we do and, of
course, they don't have the amateur population that we do either. I
don't know if it would be better or not but I do have a concern that
there are those that would intentionally blow some established CW
activities away with their own wider bandwidth signals ON PURPOSE. I'm
not only talking about ARRL CW practice and bulletins but established CW
traffic nets and such don't function very well if folks have to contend
with SSB splatter all over them.

CW traffic nets don't function well with zero QRM. CW stations are also known to interfere deliberately with CW stations.

I suppose we will live with what we get
and use the new changes as an indicator for what will come in the
future. Perhaps one day we will have all modes on all band on all
frequencies like Jim spoke of and see what happens. I will say that it
is a shame to listen to the bottom end of 40 meters and hear SSB below
7010 blowing away weak signal CW DX... That's disgusting.

That's life, Tony. cheers

.

R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Nov 11, 2006, at 10:54 AM, Robert B. Bonner wrote:

Well I do have responses for the comments.

I do currently own a 3K-A. Have had virtually all of them in the

past.

Also have owned an L4B, Swan Mark II never SB-220 or TL-922

however

I've
worked on almost everything at one time or another.

The problem with Henry's and Heath's design is the SOCKETS. The
Johnson
socket mounted below the chassis on 4 bent metal brackets is

the

problem.

### Drake uses the same Johnson sub mounted sockets on the L4B.
[came out in 1969].. on aluminium cylinder standoffs. The 3-500Z
spec is for only .08" h2o... which is easy to achieve. That's
zip..pressure wise. Drake used real Eimac SK-410's on the older
plane jane L4 [1964]

The little holes in the Johnson socket were matched to the 4-XX
series of
tubes. 4-65, 4-125, 4-250 and were designed before they

developed

tubes the
size of 4-400, 3-400, 3-500. There is inadequate cooling around

the

bases
when using these sockets with the larger tubes.

I've seen Eimac 3-500's with the letters burned off one side in
amps like
the SB-220.

RICH SEZ...I have never seen an amplifier with a cooling system

like a SB-220's.

#### Sure their is. The Ten tec Centurion uses the same deal.
The chassis is raised UP, right where the sockets are. Resembles a
small box sitting on the chassis... with two[oposing] sides chopped
out.. so air can pass UNDERNEATH...and hit all the pins. The tiny
slots in the cab are where they screwed up... really restricts air
getting in and out.

The correct Eimac air system sockets REALLY move air through

them

in all the
right places. For instance the 410's and 510's have a collar

where you

actually hook up ducted air to the base.

### agreed. A 4-1000 Deck I bought from W6RU back in 1977 was
done exactly like that. Blower mounted below... with flexible
ducting that fit that collar like a glove.

## On HB 4-1000's... I carefully removed the pins from the SK-
510 socket... then sliced off that collar with a hacksaw... re-
asembled.. then installed em. In that case... blower was on rear
apron... pressurized the chassis.

The problem is that the 3-500Z air system socket requires a high-
pressure centrifugal blower, and Ham amps used an ordinary
centrifugal blower.

### See my note above. A 3-500Z only requires a .08" h2o pressure.

Back in 1970's it was recommended if you weren't using ducted

air,

that you
disassemble the sockets and hacksaw off the collar to allow

even

better
airflow during pressurized chassis operations.

### exactly. An if using the older aluminium Eimac sockets..
like the SK-500 and SK-400... well the pressure requirements on a
SK-500 was 50% higher than a SK-510 .9" vs .6" The 500-
+400 socket had an offset for the small diam air hose. The fix
was to take socket apart... and slice the entire bottom off
transversely with a bandsaw.... then it resembled a 510/410.. with
that collar chopped off.

### On a related note. IF anybody using a 500/400 socket...
beware... there is a screw adjustment for female pin rigidity.
The 500/400 sockets used hollow female tubes to terminate the male
pins of the tube. At the base of the female tubes.. there is an
adjustment to allow some slop or play. I have seen fellows crank
these super tight... then stress the tube seals when the tube is
inserted. IF tight... you have too much lateral force on the male
pins of the tube. Once heated.. the seals will crack.... leave em
loose.

( SO... The next problem with ham designs is the
stupid covers on the amps. Drilling holes to make the boxes look

pretty. BAD airflow. The best would be cut large holes with metal
screens barely blocking the airflow path.

### You just nailed it right there ! The top lid on my L4B's
gets hot with a severe test. I removed the top lid... repeat the
test, and all is well. Some fellow in Ore did ur mod on his
Henry 5 K. Redid the entire blower setup. The other problem with
the 5k is... the holes in the chassis were too small and severely
restricted airflow from below. He increased em by a huge
amount... and also cut nice holes above EACH 3CX-1200.. and
installed those "hamburger grilles"... [4 x hole mount grates..
like u see available for ANY fan, used to keep ur finger's away
from fan blades] In this case.. the grilles are used to keep
fingers away from the anodes... yet let air pass freely... plus
they look good.

RICH SEZ... That's how I do it. I also use a varnished cardboard

flap that hinges up to let the air out. It just doesn't look as
pretty.

### It would look like hell! Now that's what I call "K-mart
construction". Rich would call it part of his.. "ugly amplifier"
scene.

### somebody.. think it was W7RF, radio dan.. supplied curved
plexiglass covers for the henry amps.. to make the exhaust air do
a sweeping right angle... facing the back... this was supposed to
kill some noise.... it would stop dust from settling in.. when not
in use.




A Heath cover is a piece of junk. They paint more of the hole area
closed than have open...

### agreed. Both Heath and Drake woulda been better off to just
made the entire top and sides solid... and 2 x big diam holes..
with fan grilles... right above the tubes.

### here's the interesting bit. Eimac states the glass tubes
cool by infared radiation.... well my natural gas fireplace puts
out loads of radiant heat.... a 3-500Z doesn't. Even though the top
lid gets hot... the sides are stone cold. None of the flat black
sides gets warm... on the inside or out... ditto with surrounding
componnents.

### For a real eye opener... a buddy close by... built a 2 x 4-1000
in gg.... that used LEAD chimney's... made by Eimac too. They
looked identical to a Eimac Glass chimney. They each had a small
teardrop shaped inspection plate on the side... that pivoted... just
like an old oil furnace. He also had the mating 4PR-1000 tubes.
Apparently, these chimney's were used on pulse rated tubes... when
extreme HV was used in pulse service.... the lead of course,
absorbed the X-rays. Never seen a lead chimney b4 or since.
Weighed a ton. Believe they were cast aluminum chimneys... with an
inner and outer lead liner.

Later... Jim VE7RF

The only absolutely guaranteed measure of correct airflow is to
measure the temperature of the tube seals as specified by the tube
manufacturer, under full load for long enough for the tube to reach
max temp at that load. Any airflow beyond that is not necessary but
may give one peace of mind.

Bill, W6WRT


------------ ORIGINAL MESSAGE ------------

On Nov 11, 2006, at 10:54 AM, Robert B. Bonner wrote:

Well I do have responses for the comments.

I do currently own a 3K-A. Have had virtually all of them in the past.
Also have owned an L4B, Swan Mark II never SB-220 or TL-922 however I've
worked on almost everything at one time or another.

The problem with Henry's and Heath's design is the SOCKETS. The Johnson
socket mounted below the chassis on 4 bent metal brackets is the problem.

The little holes in the Johnson socket were matched to the 4-XX series of
tubes. 4-65, 4-125, 4-250 and were designed before they developed tubes the
size of 4-400, 3-400, 3-500. There is inadequate cooling around the bases
when using these sockets with the larger tubes.

I've seen Eimac 3-500's with the letters burned off one side in amps like
the SB-220.

I have never seen an amplifier with a cooling system like a SB-220's.

The correct Eimac air system sockets REALLY move air through them in all the
right places. For instance the 410's and 510's have a collar where you
actually hook up ducted air to the base.

The problem is that the 3-500Z air system socket requires a high- pressure centrifugal blower, and Ham amps used an ordinary centrifugal blower.

Back in 1970's it was recommended if you weren't using ducted air, that you
disassemble the sockets and hacksaw off the collar to allow even better
airflow during pressurized chassis operations.

My Ph.D. is in Physics, I spent a lot of my career after college in the
computer industry doing chassis design for a computer company. Basically
trying to put 10 pounds of electronic maird in a 5 pound box and cool it.

Chortle. Another useful French word.

In the lab we had a lot of temp probes in computers.

This was all PRE-IBM PC... Pc designs actually are some of the worst cooled
boxes around. :-( SO... The next problem with ham designs is the stupid
covers on the amps. Drilling holes to make the boxes look pretty. BAD
airflow. The best would be cut large holes with metal screens barely
blocking the airflow path.

That's how I do it. I also use a varnished cardboard flap that hinges up to let the air out.

It just doesn't look as pretty. A Heath cover
is a piece of junk. They paint more of the hole area closed than have
open...

The glass temperature is okay no matter what skeptics say.

...
So I think Between Jim VE7RF and myself we've answered why amps like Henry,
and The Sb-220 have had pin melting issues.

Only in a SB-220 when the fan motor bearings are not kept oiled

BOB DD

-----Original Message-----
From: ham_amplifiers@... [mailto:ham_amplifiers@...]
On Behalf Of pentalab
Sent: Saturday, November 11, 2006 6:25 AM
To: ham_amplifiers@...
Subject: [ham_amplifiers] Re: 3-500Z socket.... max current ratings

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

After my first 3-500 amp when I was 16 I always used sockets

and chimneys.

RICH SEZ.... Air system sockets and chimneys result in higher glass
temperatures than is the case with the transverse-fan cooling
system used in the SB-220 and TL-922.

### Nonsense. Depends on airflow... and speed of fan..or blower.
You def will get better, more uniform cooling with a blower and
chimneys... PROVIDED u use vertical finned anode connectors. With
chimneys... u def get better cooling of the pins.

I always felt it allowed the envelopes of the tubes to evenly

cool around the tubes. The tube pins get coolest direct air.

RICH SEZ... So why does the Henry 3K-A, which uses air-system
sockets and chimneys, have a history of melting solder out of tube
pins #1 and #5 ?

### Dunno... my guess is, since the 3K-A runs 4 kv.. and >2 kw
out... that some bozo at Henry screwed up. Maybe they use lousy
sockets.. with too much contact resistance. Who knows. Their
anode connector's may well be a problem. Lot's of homebrew 3-
500Z amps with chimney's... never a problem.

### There is hardly any air going through the pyrex coleman lantern
chimney's on a L4B... with it's puny... but quiet 1550 rpm
blower. No roasted ink either.... and no one ever melted solder
on pins 1+5.

### Use some heat sensitive paint(S)... like Eimac suggests... and
you can tell pretty quick... what's within spec.

Later.... Jim VE7RF

Yahoo! Groups Links

R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org