Fellows

I have several fuses installed in most of these linear's.

Like a fast 750 ma 3agc style grid fuse... located between
chassis.. and negative terminal of 0-1 Amp grid meter.

Also have a 3 A cathode fuse [also a 3agc] in the center tap of
the fil xfmr circuit [ along with the 60 x 6A10 6-A , rotary
switched bias diodes. ] This 3 A cathode fuse has a 1k-25
watt ressitor across it.

Question is... what's an easy way to obtain a visual
indication /led/neon/etc.... to let us know said fuses are
blown ???

Most of the "visual indicating" type fuse holders I have seen...
all require use of the line voltage being fed into em... ie: 120
vac, etc.

I was thinking.. perhaps a 1-2 ohm resistor across each fuse
holder... such that the v drop across the resistor [with fuse
open] will trigger a led/etc. [this would amount to installing a
typ grid/cathode electronic overcurrent device..... except it
would only work IF the grid/cathode fuse opens].

Origionaly, we installed a 100 K- 2w-MF across the grid
fuse.... believing if the grid fuse blew.... the resulting bias
developed.. would cutoff the tube... and tube couldn't be
driven. In actual practise... with the typ globs of drive... you
can still drive the tube... albeit.. in class C ! So we
subsequently removed the 100K resistor. Now,,, if the grid fuse
opens... zero output... input swr rises from flat.. to
2:1. ..... No DC grid current.

Here's the real concern. With the grid fuse blown open.... there
is NO return for DC grid current... fine so far. But what
happens to the drive RF [800 ++ watts worth] ?? Are we burning
up the cathode.... and /or the grid ..or both ????

In all cases these RF decks/ power supplies are remote located 30-
50' away from the station. The station can however... read
all 4 bird line sections... and also continuously monitor the
PEP refelcted pwr [part of the high swr shut down circuit].

On a related note.... IF either HV fuse blow open..[1st one
in one leg of sec of plate xfmr... the 2nd in the B+].... and
with tube driven... ALL the electrons flow to the control
grid... instead of the anode... and you guessed it... the grid
current will skyrocket.. [read it will blow the grid fuse asap]

We have seen cases whereby the HV fuse + grid fuse will
blow open... cuz of an antenna problem... and high swr [trips on
high reflected pep power] circuit has NOT tripped the amp
offline.
We have also seen cases, where the high reflected power circuit
trips 1st.... and trips both linears offline.. [which also
applies -10 vdc to the ALC of the xcvr. ]

All depends sometimes... whether it's an arcing ant/badly
installed connector. [resulting in an INSTANTANEOUS wide open/dead
short... infintite swr] OR just a high swr... between 2:1
and 5:1

In some cases the B+ sandfilled fuse blows..... some times BOTH
sandfilled fuses blow.

For some added protection... we are thinking of an adjustable
spark gap between load cap ...and chassis..... set to fire at a
V higher than the normal low swr V.... and a point well below the
rating of the 5 kv vac load cap. I think Rich may have done
this ? I don't want the expensive ceramic vac load cap to ever
internally arc.

Sri for the drivel....... does anybody actually read any of my
posts....... or is this all old news ???

Later... Jim VE7RF

On Sep 29, 2006, at 1:08 PM, la3pna wrote:

I guess i need 8 resistors? but, how about the voltage drop over the
resistors? or should the resistors be so small that I don't need to
worry about that?

The V-drops across the cathode resistors is what helps to equalize the cathode currents in the 4, 811As. However, 4, individual bifilar filament chokes and 4. DC blocker/coupling caps are needed.

Since i have about 75 ohm input impedance, do I need an tuned input or
is there an easyer way to do it?

There is no substitute for the flywheel effect of a Pi-network tuned input with a Q of 2 to 3.

73 de Thomas

--- In ham_amplifiers@..., Steven Grant <w4iiv@...> wrote:

You dont need matched tubes -- just put some resistance in the
cathodes and they self match -- rich knows more about how to get the
right values of resistance -- im still learning
Steven Grant W4IIV


At 04:54 PM 9/26/2006, la3pna wrote:

Hi group.
I'm Thomas, La3PNA and I'm in the progress of starting to build an HF
amplifier with 4 811A tubes. I'm gone to use 4 of them because, I got
the tubes, sockets and Plate caps for 4. I have drawn an shematic that
can be found in the folder "LA3PNA 811 amplifier" in the Files section.

I have drawn it as an one band unit, mostly since the rotary switches
in Eagle are stupid drawn, I would like to make it work at all nine
HF bands, from 160M to 10M.

I wrote an e-mail to R L MEASURES and got an nice answer on some of my
questions. He recomended to use 5 of 811, but i think that it is a bit
hard to get 5 matched tubes?

I have found out that one 811 tube has an impedance of 300 ohm's so 4
of them should give an inpedance of 75 ohms. Is this correct? found
the data in an old ARRL handbook, on an article on an one tube amp.

Hope that some of you have time to take an look at my design and
please let me know if there is any errors.

73 de Thomas LA3PNA
PS: sorry for my bad English.

Yahoo! Groups Links

I had some problems with the selection, so here is the direct link to
rest of the world:


73 de Thomas

fre, 29,.09.2006 kl. 15.34 -0400, skrev Tony King - W4ZT:

--
Best Regards/MVH
Thomas S Knutsen
LA3PNA

Gents

A few years back... after consulting with John Lyles about my idea,
I decided to try it... it works !

Nothing really new here... but thought I'd pass along this info...
since you will never see it in any edition of the "ARRL
Handbook" any time soon.

We purchased two Type 43 ferrite rods [on sale at the time
from SSON] each 1/2" diam x 8" long. Also got the plastic
nylon re-enforced 1/2" clamps for each end of the rods.

Using some 10 ga polyimide magnet wire [on sale... u can find
plenty of cheap sources for magnet wire on the web].... we
bifilar wound the 10 ga magnet wire on 1/2" diam x 12"
long aluminium tubes.... leaving lots of pigtails at each end.
DON'T wind em on the brittle ferrite rods !!!

We then simply slipped the completed windings off the aluminium
tube... onto the ferrite rods... then installed the plastic
clamps at each end. Next, compression crimps/clamps were crimped
+ soldered on all the 4 x pig tails.. [after chopping excess
pigtails]

Two identical such assy's were built.

Now here's the kicker. To handle the 50 A of fil current in a
3CX-3000A7.... we had to parallel the 2 x bifilar's. [which will
then handle 60 A CCS] .

In order to still maintain Bifilar action [OPPOSING currents
flowing in EACH individual winding... of EACH rod] .. we
paralled ANY one winding from ROD-1.... with ANY one winding
from ROD-2.... and vice versa for the 2 x remaining windings.
This is done so the magnetic fields generated in each winding
will CANCEL.... and NO rod saturation will occur.... hence the
1/2" rod material is plenty.

Note: single wound rods WILL saturate the rod. Back in the
old days.... fellows would laminate a bunch of rods together...
like a bundle of dynamite... and then wind a single winding on
this mess. They built two such assy's.... one per leg.... that
was back in 69 !

Now... if u draw this out on paper... you can easily see that the
50 A of fil current splits into two paths... with 25 A of
current flowing in the "one winding per rod".... then
recombined.... feeds one side of fil..... out the other side of
the fil.... splits back into two paths.... 25 A back down each
rod... then again recombined ... and back to fil xfmr.

This works superb on 160-10m.


On the 80A fil [ for a 3CX-6000A7 /YC-243] just use 8 ga
magnet wire... instead of 10 ga. The paralled 8 ga handles
80A CCS all day long.. stone cold. Semi-moot point...since the
bifilars will be blasted with air from the blower anyway !

Beware....on the 3CX-3000A7.... you will lose aprx .3 to .4 V
ACROSS the bifilar. [rated at 7.5 V @ 50 A] .... and .3 V on
the 3CX-6000A7 /YC-243 [rated at 7.0 V @ 79 A]

We used 6 ga wire FROM the 50 A fil xfmr..... and 2 ga from
the 80 A fil xfmr... located in next shelf BELOW the RF Deck.
This method eliminates an additional 23 lbs from the RF deck,
which makes life easier on my back.


An alternate method is to simply install small 3-4 A CCS rated
bifilar chokes in the 120/240 v PRIMARY of the fil xfmr. In
this case... the fil xfmr HAS to be installed on the RF deck...
below trhe chassis... AND insulated from the chassis.. as it will
be hot with drive RF. This can easily be done with two
laminated sheets of micarta/ uhmw/etc. Use recessed screws to
mount the xfmr to the 1st sheet.... laminate a 2nd larger sheet
to the 1st... then bolt the 2nd sheet to the side wall below the
chassis. Also, ALL leads.. BOTH prim and sec have to be
bypassed to the fil xfmr metal casings... with .01uf disc ceramic
caps.

This alternate method has worked very well for years.... it's
only drawback is the additional weight of the fil xfmr itself on
the RF deck.

I don't see any magnet wire larger than 8 ga available.. anywhere..
so for 100 /160A fil requirement's [ 3CX10,000A7....
3CX15/20,000A7..... this alternate method is your only option.

BTW.... measured inductance of the 10 ga bifilar... [with
both bifilars wired in parallel as depicted] measures 38 uh.
On the 8 ga bifilars wired in parallel... it's down to 25 uh....
both are plenty on 160m.

Of course, .01 uf bypass caps are used on the 'cold ends' of
the bifilar windings.

Later... Jim VE7RF

I guess i need 8 resistors? but, how about the voltage drop over the
resistors? or should the resistors be so small that I don't need to
worry about that?

Since i have about 75 ohm input impedance, do I need an tuned input or
is there an easyer way to do it?

73 de Thomas

Just in case anybody is interested.... RF Parts has a sale on MANY
of their tubes.... both triodes... + tetrodes.

eg- Svetlana 3CX-3000A7 $695.00
Svetlana 3CX-6000A7 $855.00 [reg $975.00] !

Of course the above tubes require the expensive socket/grid
ring combo.... another $375.00 !! ouch !

Arnold Howell of Howell tube sales, sells the infamous Eimac
YC-243 [socketless 3CX-6000A7] for around $1100.00.... which
is IMO.. the best bargain of all.... comes with a built in 1/8"
thick, silver plated grid flange.. 4.25" diam........ and two...
just huge fil lugs. [5/16" threaded, embedded studs].

Both the 3CX-6000A7 + YC-243 are the sleeper of the year !
Although rated for 6 kw anode diss [205 cfm @ .4" water..
at an inlet air temp of 50 deg C].... this stock anode rating
can EASILY be increased to almost 9 kw.... simply by blowing more
air through it, and using a lower inlet air temp, and using a 9"
square box around the tube.. with a teflon top. [310 cfm @ .9"
water at an inlet air temp of 25 deg C]. A Dayton 5C508 dual
speed blower fits this requirement perfectly.




The YC-156 medical MRI pulls... can still be had from Norman
Hockler..[N8NH]... who also has the mating fil xfmr's.. SK-306
chimney's, etc. Norm also has new globars... 90 watt CCS...
glass bodied SP type... 3/4 " diam x 5" long.. 50 ohm. We use
these for parasitic suppressors... just wind em with 3 turns
of 3/4" wide strap... and install em in standard 3/4" silver
plated fuse holders...with end retainers. The SP globars
are good for 350 deg C... CCS ! ZERO fireworks, ultimate
parasitic suppressor....Rock stable.

Norm sells the YC-156's for aprx $375.00 - $450.00. These are
a 3CPX-15,000B7... with a 5 kw ..4.94" OD cooler.... built in
grid flange... no socket required.... and almost 19db of gain !

You fellow's who want a "project" this fall/winter.... well here
you go !

Later.... Jim VE7RF

The actual link is: <>

73, Tony W4ZT

Frank Goenninger wrote:

Hi Mike and all:

Am 29.09.2006 um 20:04 schrieb Mike(W5UC) & Kathy(K5MWH):

There is a site called The Wayback Machine, and references to old
or outdated URL’s are stored there. It can be found at:
www.archive.org/web/web.php

Wow ! Thanks for the pointer!

I went to where I got the inactive Svetlana URL(above) and plugged
it in to The Wayback Machine and it found several stored references
to the page. I printed the article from the internet page. I then
tried to copy & paste it into Word, but it came out all funky. If
you have trouble let me know and I will scan it and send it to you.
I think the original article appeared in CQ, but I don't know the
date. Good Luck.

Using the Mac OS X built-in PDF creator I made a PDF and uploaded it
to the files section of this group (Hey I love my Mac!). If someone
needs another one from another page/ document please let me know. I
also have Adobe Acrobat Professional so copying text passages or
images from within a PDF is possible for me, too. Just drop an email
and I'll see what I can do.

73, Frank DG1SBG

开云体育

Duh!

-John, N9RF

Am 29.09.2006 um 19:09 schrieb Tony King - W4ZT:

pentalab wrote:
<snip>

### I can't get into Svetlana's site either.....

I had this same problem... it insisted that since I was in the USA there
was nothing there for me. That was using my favorite browser, Firefox.

I opened the dreaded Internet Explorer, which I NEVER use, and it went
there just fine. Do NOT click on USA as your location. Select rest of
the world.

73, Tony W4ZT

??? How did achieve that? For me the query for the host www.svetlana.com itself does not work (using low level tools like nslookup [name service lookup] yields a "server unknown" message with a SERVFAIL (meaning the query did fail - not "there's no entry for www.svetlana.com). Strange, that!

Tony, could you post a link other than the bare www.svetlana.com that works for you? Thanks!!

73 Frank DG1SBG

--- In ham_amplifiers@..., "kr4da" <kr4da@...> wrote:

Passed the 100 total members mark this week.

de KR4DA Bob

### Now at 104 member's..... I'd say vehemently.... that
Rich, and anybody else who has ever either.. been booted
off 'amps'.... or had their posts trashed... or edited.....or
deleted.... has finally been vindicated !!

### This group has THE distinct advantage...... throwing in
stuff like jpegs, pix, schematics.. polls, and files, is just
gravy.

### My prediction was, [and still is] this group would grow
in leaps and bounds..... and leave 'amps'... in the dust.

## IF W8JI, et all... ever show up here.... it will
be..."poetic justice".

Later..... Jim VE7RF

pentalab wrote:
<snip>

### I can't get into Svetlana's site either..... have not been able to.... for a couple of yrs at least. I printed out some of their stuff but not what u need. What's the deal ? Svetlana's site was superb.... showing u insides of tubes, etc. Jim VE7RF

Does anyone have this conversion info or can someone out of the US

retrieve

the info and forward it to me.

Many Thanks
73,

Mike, W5UC

I had this same problem... it insisted that since I was in the USA there was nothing there for me. That was using my favorite browser, Firefox.

I opened the dreaded Internet Explorer, which I NEVER use, and it went there just fine. Do NOT click on USA as your location. Select rest of the world.

73, Tony W4ZT

--- In ham_amplifiers@..., "Mike&#92;(W5UC&#92;) &
Kathy&#92;(K5MWH&#92;)" <w5uc@...> wrote:

Good Evening All:


There is a Svetlana page with the info on it but I am told that we
in the US are presently unable to access that site at

### I can't get into Svetlana's site either..... have not been
able to.... for a couple of yrs at least. I printed out some of
their stuff but not what u need. What's the deal ?
Svetlana's site was superb.... showing u insides of tubes, etc.

Jim VE7RF

Does anyone have this conversion info or can someone out of the US

retrieve

the info and forward it to me.



Many Thanks



73,

Mike, W5UC









_____

Bob -- It would be interesting to compare this with the AMPS total, but that information has been kept secret ever since someone who got booted off of AMPS by the moderator/censor, downloaded the members e- mail addresses, bypassed the moderator/censor, and started posting direct to members.
I think it is pretty safe to say that censorship will never be very popular in America.

cheerz

Passed the 100 total members mark this week.

de KR4DA Bob

开云体育

Silicone rubber is used to insulate HV wiring.

I'm repairing a Bird 5000H element (2-30 MHz 5 KW) and the resistor in
the slug appears to be wrong. What is the nominal resistor value for
this element?

TIA

Does this mean there is no problem with routing the silicone cooling lines
out of the HV end of the line?

-John, N9RF