Another piece of ham lore is -- if you run the heater for a day, the getter will get hot and absorb the gas.
That's worth a try, and won't set your backyard or basement on fire.
73 Jim N6OTQ
On Fri, Sep 8, 2023 at 10:07?AM Chuck Neal < cdoneal@...> wrote: The tube is likely gassy and will only conduct when HV is applied.? It usually takes a few hundred volts for a gassy tube to conduct so the low voltage from a test meter will not reveal a gassy tube. ? Hint:? Watch the tube upon applying HV.? You might see a quick bluish flash before the fuse goes. ? -Chuck K1KW ? From: [email protected] [mailto:[email protected]] On Behalf Of Bob
Sent: Friday, September 08, 2023 10:21 AM
To: Ham Amplifiers Ham Amplifiers
Subject: [ham-amplifiers] 572B ? Hi all, I'll condense this, you'lll get the idea. A friend has an 811H with 3 year old 572B's. One shorted?and causes the fuse to blow immediately. Tube replaced and all is well. Measuring with a DVOM shows no shorts at all. I do know some tubes will short after they get warm/hot but this one blows the fuse immediately (no time to get hot) but does not measure any short circuit. I've now talked to two other hams on the air that say the exact same thing happened to them.
|
That's prolly the answer. I put my friends amp back together so I cannot test it now plus it obviously puts stress on everything so I'll mark it bad and test it at a later date. Your theory makes sense. Thanks. Bob W4JFA?
On Fri, Sep 8, 2023, 11:07 AM Chuck Neal < cdoneal@...> wrote: The tube is likely gassy and will only conduct when HV is applied.? It usually takes a few hundred volts for a gassy tube to conduct so the low voltage from a test meter will not reveal a gassy tube. ? Hint:? Watch the tube upon applying HV.? You might see a quick bluish flash before the fuse goes. ? -Chuck K1KW ? From: [email protected] [mailto:[email protected]] On Behalf Of Bob
Sent: Friday, September 08, 2023 10:21 AM
To: Ham Amplifiers Ham Amplifiers
Subject: [ham-amplifiers] 572B ? Hi all, I'll condense this, you'lll get the idea. A friend has an 811H with 3 year old 572B's. One shorted?and causes the fuse to blow immediately. Tube replaced and all is well. Measuring with a DVOM shows no shorts at all. I do know some tubes will short after they get warm/hot but this one blows the fuse immediately (no time to get hot) but does not measure any short circuit. I've now talked to two other hams on the air that say the exact same thing happened to them.
|
The tube is likely gassy and will only conduct when HV is applied.? It usually takes a few hundred volts for a gassy tube to conduct so the low voltage from a test meter will not reveal a gassy tube. ? Hint:? Watch the tube upon applying HV.? You might see a quick bluish flash before the fuse goes. ? -Chuck K1KW ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Bob
Sent: Friday, September 08, 2023 10:21 AM
To: Ham Amplifiers Ham Amplifiers
Subject: [ham-amplifiers] 572B ? Hi all, I'll condense this, you'lll get the idea. A friend has an 811H with 3 year old 572B's. One shorted?and causes the fuse to blow immediately. Tube replaced and all is well. Measuring with a DVOM shows no shorts at all. I do know some tubes will short after they get warm/hot but this one blows the fuse immediately (no time to get hot) but does not measure any short circuit. I've now talked to two other hams on the air that say the exact same thing happened to them.
|
Rich Measures (SK) wrote about this, and suggested (for different tubes) a possible way to fix it by swinging a live tube around your head.? I guess if you do it outdoors and the tube is already shorted, then no harm, no foul, right? ? Tom Rauchen Verboten?W8JI has more to say.? Locate his web site and read to your heart's content -- after Measures passed, Tom corrected all of his own errors and added a whole lot of new, better info.
Basically, this is usually caused by the grid not being concentric with the cathode / heater.? When the tube gets hot, the grid softens at red heat and falls into the cathode, thus shorting it.? When the grid cools, it welds itself to the cathode and the tube is toast forever.? Unless, of course, you want to try exciting the cathode and swinging the tube around your head once it gets good and hot. ?
This must have worked at least once, or else Measures wouldn't have published it.? For my part, I don't think it's a very good idea, because it's a red-hot lump of metal encased in glass, and my back yard is full of vintage sports cars and antenna structures.? And dry brush.? It hasn't rained here all summer and it's only a matter of time before everybody in the city?burns down their back yard.
If you don't mind burning down your basement, you might put an ohmmeter between the grid and cathode to confirm the short, and then get the cathode hot.? By bumping the tube with some force against a padded surface and giving it 1/8 of a turn each time, you MIGHT knock loose?the weld,?as shown by the ohmmeter indicating an open circuit.
Or you might try the anti-barnacle trick, which is to put a high-voltage, high-current charge across the grid and cathode, and evaporate the weld.? Whatever you do, keep in mind that this tube is dead and is good for nothing more than a night light now. ? So have fun, be safe, and you might get lucky enough to break loose the weld and have a usable tube again.? But don't bet the farm on it.
73 Jim N6OTQ?
Hi all,
I'll condense this, you'lll get the idea.
A friend has an 811H with 3 year old 572B's. One shorted?and causes the fuse to blow immediately. Tube replaced and all is well.
Measuring with a DVOM shows no shorts at all. I do know some tubes will short after they get warm/hot but this one blows the fuse immediately (no time to get hot) but does not measure any short circuit.
I've now talked to two other hams on the air that say the exact same thing happened to them.
What causes this??
73, Bob? W4JFA
|
Re: Operating RTTY FSK and Alpha 86
Jim, ? Can you point us to a good filter material to use?? Maybe a link? ? Jim – KR9U ?
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From: [email protected] < [email protected]> On Behalf Of Jim VE7RF Sent: Friday, September 8, 2023 1:13 AM To: [email protected]Subject: Re: [ham-amplifiers] Operating RTTY FSK and Alpha 86 ? This is exactly why you install or retrofit a filter on the air intake.?
On a side note, a shop vac on the bottom of the tube will get most of the crud + dust out...from the bottom.? ? Then try compressed air from the top. Then stick it in the dishwasher....that works superb.? ? Go to 3M's? home page.? ?They make filters as small as 7" x 7".? ?They also have washable, and cutable filters, that can be cut to fit a specific size.
Don't get ur fingers on the ceramic.? Any skin oil / fingerprints etc, will result in reduced hi-pot test results.
Jim? VE7RF
|
Hi all,
I'll condense this, you'lll get the idea.
A friend has an 811H with 3 year old 572B's. One shorted?and causes the fuse to blow immediately. Tube replaced and all is well.
Measuring with a DVOM shows no shorts at all. I do know some tubes will short after they get warm/hot but this one blows the fuse immediately (no time to get hot) but does not measure any short circuit.
I've now talked to two other hams on the air that say the exact same thing happened to them.
What causes this??
73, Bob? W4JFA
|
Re: Operating RTTY FSK and Alpha 86
This is exactly why you install or retrofit a filter on the air intake.?
On a side note, a shop vac on the bottom of the tube will get most of the crud + dust out...from the bottom.? ? Then try compressed air from the top.
Then stick it in the dishwasher....that works superb.? ? Go to 3M's? home page.? ?They make filters as small as 7" x 7".? ?They also have washable, and cutable filters, that can be cut to fit a specific size.
Don't get ur fingers on the ceramic.? Any skin oil / fingerprints etc, will result in reduced hi-pot test results.
Jim? VE7RF
|
Re: Operating RTTY FSK and Alpha 86
Gents,
?
{S N I P}
... make sure you check the tubes occasionally for a buildup of dust in the cooling fins.? Don’t simply look at the bottom of the tubes, but pull
them out and look through them at a light...
{S N I P}
?
?
Oh Jeff is so right.....
Remember when probably most everyone smoked?
?
The insides of radios collected the tar, and the
fins in the tubes would, too.
?
The only solution was to flush the anode coolers
with solvent: Yuuchh!
?
Manny who used to run Zonum out in sunny Cal would
chat about BC rebuilds where the first step was a soap and
hot water flush, and how the whole shop would smell
like an ashtray!
?
I bet a ’15,000 would get a boatload O’Goo built up!
?
Hal
W4HBM
?
?
|
Re: Operating RTTY FSK and Alpha 86
Of those two specs, the GRID current is the most critical.?
Protect against high grid current at all costs.
73/jeff/ac0c
alpha-charlie-zero-charlie
On 9/7/2023 12:49 PM, James Wolf wrote:
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One other thing Ron,? make
sure you check the tubes occasionally for a buildup of dust
in the cooling fins.? Don’t simply look at the bottom of the
tubes, but pull them out and look through them at a light.?
I know many a tube that was
toasted because of this.
?
Jim – KR9U
?
?
The muffin fan on the back is
the optional fan.? The optional fan adds to the air flow
through the tubes and a lot of air movement around the
transformer.
?
Jim – KR9U
?
?
Thanks for your reply. My 86 has
the blower and a fan on the rear panel. Is there
another fan that can be installed? The blower does
have ducting to the tubes.
There’s no problem
running RTTY on this amp.
If you keep the grid
current under 40 ma and the plate current under 875ma,
you will still make rated power and the tubes will last
forever.? If it doesn’t have the optional fan, install
it.?
?
Jim – KR9U
?
?
Hi,
New to RTTY. Looking to see what I need to know regarding
the use of the Alpha 86 and FSK on RTTY at recommended
power settings if any.
73
Ron
KK7GO
|
Re: Operating RTTY FSK and Alpha 86
One other thing Ron,? make sure you check the tubes occasionally for a buildup of dust in the cooling fins.? Don’t simply look at the bottom of the tubes, but pull them out and look through them at a light.? I know many a tube that was toasted because of this. ? Jim – KR9U ?
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From: [email protected] < [email protected]> On Behalf Of James Wolf Sent: Monday, September 4, 2023 11:32 PM To: [email protected]Subject: Re: [ham-amplifiers] Operating RTTY FSK and Alpha 86 ? The muffin fan on the back is the optional fan.? The optional fan adds to the air flow through the tubes and a lot of air movement around the transformer. ? Jim – KR9U ? ? Thanks for your reply. My 86 has the blower and a fan on the rear panel. Is there another fan that can be installed? The blower does have ducting to the tubes.
There’s no problem running RTTY on this amp. If you keep the grid current under 40 ma and the plate current under 875ma, you will still make rated power and the tubes will last forever.? If it doesn’t have the optional fan, install it.? ? Jim – KR9U ? ? Hi,
New to RTTY. Looking to see what I need to know regarding the use of the Alpha 86 and FSK on RTTY at recommended power settings if any.
73
Ron
KK7GO
|
Re: 12 KW CCS ON 160-15M...USING THE 3CX-6000A7... PART 2
On your tetrode, you are matching 50 ohms to? 1000 ohms (now 500 ohms), so the PI net values are all different........ vs? the 50 ohms to 50 ohms on the 3x6 (and 3x3).?
When matching to 500 ohms, the C1 and C2 values are a lot less, but the coil is a lot bigger.? The 4x10 ( and 4x5) tube has 100 pf of tube C? (control grid to cathode)? that has to be absorbed into the? C2 cap on the PI tuned input.? That alone creates another big problem, since then the loaded Q of the tuned input has to be increased by a bunch.....esp on upper HF bands.? ? On 15m, with a Q of 20, the C1 =? 530 pf. Coil is just .55 uh.? C2 =? 123 pf ( and the tube is 100 pf, so the required C on the C2 cap is now just 23 pf).?
?
On lower bands, you can use as low as an overall network Q of 4.5 on? ?160m + 80m.? On 80m C1 = 94 pf? L = 9.31 uh? ?C2 = 183 pf ( - 100 pf of tube C,? C2 is actually just 83 pf).??
On 160m,? C1 = 195 pf? L = 19.22 uh? ?C2 = 380 pf ( - 100 pf of tube C and C2 is actually 280 pf).? ? Required L on the 10-15 kw output tank is huge.? ?Now I can see why Asamoto? made it a 80-15m amp.? The required kintronics roller coil for 160m won't even fit.? The tuned input would be a mess on? 12+10m.?
?
And if a 1:9 un-un used...along with a 450 ohm globar resistor,? you still have to cancel out the? 100 pf of tube C.? ?That 100 pf of tube C is directly in parallel with the 450 ohm resistor.? You would need a different value of coil, directly in parallel with the 450 ohm resistor, to cancel out the 100 pf of tube C.? ?And the XC of the fixed 100 pf of tube C will? change on each band, being highest XC value on the lowest bands....and lowest XC? value on upper HF.? ?Lower HF gets the bigger coil values.? ?You got lucky with no neutralization required.? That's a major pita on a 4x5/10/15.? The small neutralization cap interacts with the tuned input. ( they throw each other off).? To tweak it up right, Scott had to use a Boonton RF voltmeter, + sig generator.? ?Regulated screen and bias supplies? + protection is no mean feat.? ?Lose the B+, and with screen voltage still present, you better have super fast protection installed.? ( Both screen and anode over current...and also grid over current).?
Dunno what the chinese 3x3 and 3x6 cost these days.? ?The tuned input is dead simple. On the 3x6, it needs an IPA.? With the mini turns counter + 6:1 vernier on both the tune and load caps on any SB-220 / L4B, it makes for dialing up pre-sets a snap, mere seconds.? Any SS IPA is even faster.??
?
So, yes, there is tradeoffs with a tetrode / triode.? In it's simplest format, the triode + IPA wins out.? ?Watch how the build progress's.?
|
Re: Operating RTTY FSK and Alpha 86
Morning Jim
Got it. Thank you
Ron
KK7GO?
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Show quoted text
The muffin fan on the back is the optional fan.? The optional fan adds to the air flow through the tubes and a lot of air movement around the transformer.
?
Jim – KR9U
?
?
Thanks for your reply. My 86 has the blower and a fan on the rear panel. Is there another fan that can be installed? The blower does have ducting to the tubes.
There’s no problem running RTTY on this amp.
If you keep the grid current under 40 ma and the plate current under 875ma, you will still make rated power and the tubes will last forever.? If it doesn’t
have the optional fan, install it.?
?
Jim – KR9U
?
?
Hi,
New to RTTY. Looking to see what I need to know regarding the use of the Alpha 86 and FSK on RTTY at recommended power settings if any.
73
Ron
KK7GO
|
Re: Operating RTTY FSK and Alpha 86
The muffin fan on the back is the optional fan.? The optional fan adds to the air flow through the tubes and a lot of air movement around the transformer. ? Jim – KR9U ?
toggle quoted message
Show quoted text
From: [email protected] < [email protected]> On Behalf Of Ron KK7GO Sent: Monday, September 4, 2023 5:05 PM To: [email protected]Subject: Re: [ham-amplifiers] Operating RTTY FSK and Alpha 86 ? Thanks for your reply. My 86 has the blower and a fan on the rear panel. Is there another fan that can be installed? The blower does have ducting to the tubes.
There’s no problem running RTTY on this amp. If you keep the grid current under 40 ma and the plate current under 875ma, you will still make rated power and the tubes will last forever.? If it doesn’t have the optional fan, install it.? ? Jim – KR9U ? ? Hi,
New to RTTY. Looking to see what I need to know regarding the use of the Alpha 86 and FSK on RTTY at recommended power settings if any.
73
Ron
KK7GO
|
Re: Operating RTTY FSK and Alpha 86
?
Dear Jim, (et al),
?
Nice to see a good suggestion about running RTTY
through an amplifier, e.g., TubeMax.
?
I run an Alpha 76A with a coupla 3CPX800A7’s
with an outboard supply, and the W7RY triode
board is set to clap me on the head if I misbehave.
?
Hal Mandel
W4HBM
|
Re: Operating RTTY FSK and Alpha 86
Thanks for your reply. My 86 has the blower and a fan on the rear panel. Is there another fan that can be installed? The blower does have ducting to the tubes.
Ron - KK7GO?
toggle quoted message
Show quoted text
There’s no problem running RTTY on this amp.
If you keep the grid current under 40 ma and the plate current under 875ma, you will still make rated power and the tubes will last forever.? If it doesn’t
have the optional fan, install it.?
?
Jim – KR9U
?
?
Hi,
New to RTTY. Looking to see what I need to know regarding the use of the Alpha 86 and FSK on RTTY at recommended power settings if any.
73
Ron
KK7GO
|
Re: Operating RTTY FSK and Alpha 86
There’s no problem running RTTY on this amp. If you keep the grid current under 40 ma and the plate current under 875ma, you will still make rated power and the tubes will last forever.? If it doesn’t have the optional fan, install it.? ? Jim – KR9U ?
toggle quoted message
Show quoted text
From: [email protected] < [email protected]> On Behalf Of Ron KK7GO Sent: Monday, September 4, 2023 12:03 PM To: [email protected]Subject: [ham-amplifiers] Operating RTTY FSK and Alpha 86 ? Hi,
New to RTTY. Looking to see what I need to know regarding the use of the Alpha 86 and FSK on RTTY at recommended power settings if any.
73
Ron
KK7GO
|
Re: Kenwood TL-922-Need a plate current meter.
I had to do that as well. A little Dremel and a few seconds. Lou does a good job with those replacement meters. Bob W4JFA?
On Mon, Sep 4, 2023, 3:50 PM Jim McPhee < jmcphee@...> wrote: Hi Bob,
You asked that I let the group know how things went. Lou sent the meter, and a soft key module, and both are installed and working perfectly. And the new meter looks just like the original. The one glitch I did encounter is the terminal posts on the new meter are longer than those on the original. As a result, the positive terminal contacted the metal tray that the meter circuit board resides in, preventing the meters from being mounted back in place. I removed the meter and ground both terminals down about as short as they could be and still clamp the ring terminals under the top nut and washer. That fixed the problem. I'd recommend anyone mounting a replacement meter to do? the same before attempting to install the meter.
--
Jim McPhee
Placitas, NM
W5ABA
|
Re: Kenwood TL-922-Need a plate current meter.
Hi Bob,
You asked that I let the group know how things went. Lou sent the meter, and a soft key module, and both are installed and working perfectly. And the new meter looks just like the original. The one glitch I did encounter is the terminal posts on the new meter are longer than those on the original. As a result, the positive terminal contacted the metal tray that the meter circuit board resides in, preventing the meters from being mounted back in place. I removed the meter and ground both terminals down about as short as they could be and still clamp the ring terminals under the top nut and washer. That fixed the problem. I'd recommend anyone mounting a replacement meter to do? the same before attempting to install the meter.
--
Jim McPhee
Placitas, NM
W5ABA
|
Operating RTTY FSK and Alpha 86
Hi,
New to RTTY. Looking to see what I need to know regarding the use of the Alpha 86 and FSK on RTTY at recommended power settings if any.
73
Ron
KK7GO
|
Re: 12 KW CCS ON 160-15M...USING THE 3CX-6000A7... PART 2
Not bad on the switch. Its worth the money For a tube like this.? Input sound standard. Similar to mine but less spacing on caps.? Also not band switched but just 14 taps of inductance from an air dux coil.? If you are going to only run ham bands and never
outside that would be easier to just tap it once for each band.
The big triode thing I don't get. You could use a 4cx3000, 4cx5000 and use the radio as drive.? Grounded screen. Screen keyed. All ya need is a screen transformer, Diodes caps and a relay.? ?
I think the big triode thing comes from CBers.? Then they can over drive the Triode and make more square waves to move the bird meter.? ?Why run and amp into an amp, Now you gotta tune both.? I guess if it was a solid state modern amp that followed the radio
around, it would be ok I guess.??
Are these 3x6's cheap and plentiful?
C
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Type 90 switch is? just under $500.00? ? It's rated at 40 amps @ 20 kv.? ?Scott doubled up on the contacts, and made it into 80 amp switch.?
I used a triple wafer model 88, and paralleled all 3 x wafers.? Modified into a progressively shorting switch by installing? 5 pole? sequential rotors on each wafer.? The 88 is rated at 30 amps @ 13 kv. With 3 x wafers in parallel it's now 90 amps @ 13 kv.
Triple wafer model 85 switches will also work. 30 amps @ 12 kv.? ?90 amps @ 12 kv? with 3 x wafers in parallel.? ?Beware, those current ratings are for 60 hz AC...not RF freqs.? The triple wafer model 85 / 88 are reasonably priced.
Tubing in the plumbing section of Home depot (aisle 16) is dirt cheap.? I silver plate em with the cool-amp glop from Ore.?
The correct? KINTRONICS 40 amp (1/2" tubing)? ?roller coil, new is $1821.00? ? Called a LV19-40.? ( 19 uh).? ? Damned thing is massive,? ? 17.625" long x? 11.625" wide? x? 11.5" tall.? ?Not including shaft out the end. Plus must be mounted on 4 x 6" tall standoffs.?
?Total height is then 17.5" tall. That just kills it for any amp...period.? You need a chassis the size of a dump truck.? I would take the Kintronics roller coil ratings with a grain of salt too.? The actual rolling contact is the weak point on em.? The fixed
tubing Kintronics coils are rated the same as their roller counterparts...which nobody else does.? Everybody else always de-rates the roller versions.? Since the roller is variable, required uh is easy to obtain. BUT the tubing used has to be sized for upper
HF, which means 1/2" tubing.?
On this setup, the 2.3 uh coil is 1/2" tubing....and combines the .6 uh pre-coil / L coil and the 1.75 uh 20m coil, all in one coil. 20m Coil tapped for 17+15M. The required uh for 80m is? ?9.25 uh.? 80m coil is just 7.5 uh, since? the 1.75 uh 20m coil is
already in series with it.? 160 required uh is 18-18.5 uh.? ?A simple 9.25 uh 160m coil is on the end of the mess.
Scott got lucky, and has a box full of silver plated 2.3 uh tubing coils, made from 1/2" tubing.? They all came from 13.56 mhz RF generators.?
?
20-17-15m coil is made from 1/2" tubing.? 80-40m coil is made from 3/8" tubing.? ?160m coil is made from 1/4" tubing.?
Any roller...... (or tubing coils in series, and bandswitched)? that covers down to 160m is gonna create grief.? ?You will get the dreaded ....'suck out' on 20-10m every time.? That's why we use a progressive shorting style bandswitch if 160m is involved.?
Multi-tech industries calls those switches.... 'multiple pole rotors'.? ?IE: instead of a single rotor, they use 5 x sequential rotor fingers...that all converge onto the central rotor hub.? ?1st rotor finger does the actual various taps, the remaining fingers
just provide for additional shorts across un-used contacts.? ?You can test for? suck out very easily.? Temp wire a resistor ( = to the plate load Z) between anode to chassis.? Tweak tune and load and roller for 160m..with mfj-259B on output connector for 1:1
swr.? Then sweep the mfj and see what the upper /lower freq is for the 2:1? points.? ?Then repeat on 80m.? On 80m, the 2:1 points should be twice the BW.? And double again on 40m.? And double again on 20m. With suckout, the 2:1 BW is extremely narrow. Temp
short out the last few turns at the 160m end of the roller...and the suckout effect? vanishes.?
?
On a roller that covers 160m, the only option is to use a relay, and it's contacts, to provide for one extra short in the middle of the coil, like where 80m would reside.?
?
Tetrodes are a? pita.? ?The 4x5 has a tiny under fin area? vs the 3x6.? It's dead simple to get 8 kw CCS anode diss from a 3x6. No screen supplies required, nor bias supplies, nor? screen grid protection.? (Lose the B+, with screen V still present, and you
are in for a rude surprise).? ?3x6 is simple resistor cut off bias.? No neutralization required.? ?On my own YC-243, it's a socketless version of a 3x6.? ?Build in grid? flange just bolts to the chassis.? 50 ohm input. Simple tuned input. Fil choke is now
dead simple....just slide on the fair rite oval beads over the pair of power cables.? Simple metering. Sorta like a SB-220 on steroids.
?
Scott already has a 4x15 installed in his aerocom commercial amp.? Damned thing idles at 1000 ma ! (@ 8 kv).? ?Sucks 3 kw on RX....and 10 kw when keyed, on idle....and no drive applied.? And sucks 45+ kw when driven.? 3 x blowers used.?
It uses a 75 kva pole pig configured for 240 input and 5600 vac output.? You need 400 amp service to run it.? ?Totally impractical.? ?It's going up for sale at some point.
?
Sure, a small IPA is required with the 3x6.? ?Everybody already has a 600 watt amp.? 80% of the drive power ends up in the output.
?
Here is the 4x15 aerocom amp.?
Here is the 75 kva plate xfmr that runs it.? ?
?
?The new cabinet is pretty small for this project.? ?It will all just barely fit.? Cab height, from chassis to top is only 9.25".
? Ok, that's the sob story for this week.?
|
Bob
HaL Mandel