Re: Artificial centre tap for GG 3CX1200
Dear ‘1200 Builder,
?
When dealing with Heavy Iron it is not wise to
Jury-Rig.
?
Save for the ability to purchase the right iron.
?
In fact, HARBACH may just have the perfect item in
stock, or would be able to wind up something in a heartbeat.
?
Hal Mandel
W4HBM
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Re: Artificial centre tap for GG 3CX1200
A 6.3 VAC @3A ?CT transformer will work just fine.? That’s what I used ? -Chuck K1KW ? ? ?
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From: ham-amplifiers@groups.io [mailto:ham-amplifiers@groups.io] On Behalf Of va3dxv
Sent: Friday, December 01, 2023 5:07 PM
To: ham-amplifiers@groups.io
Subject: Re: [ham-amplifiers] Artificial centre tap for GG 3CX1200 ? On Fri, Dec 1, 2023 at 11:58 AM, Chuck Neal wrote: Yes I have done this and it works very well. Ahh that's good to hear, Thanks! Any idea on whats needed of the required transformer? I'm kind of thinking that as long as the winding can handle the DC current, and doesn't have a huge DC resistance, then it's probably ok? Like a 12V 1A maybe?
I'll poke around and see how easy it would be to add a CT, didn't really consider that at first, but yeah. Thanks Guys.
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Re: Need Help with Amp Supply LK500ZC
The clue is surely in the grid current reading. It should be zero with no drive.
73, Alek VK6APK.
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On 2/12/2023 5:49 am, Adrian Fewster wrote: I had asked for that. what is the same result for each tube on its own with the other removed ?
Also voltage across zener keyed and unkeyed ?
73
vk4tux
On 2/12/23 06:47, John Roland wrote:
Someone asked about idling current.? With no drive but the amp keyed I'm seeing about 80 ma? plate current and about 30 ma grid current.? Both meters drop to 0 when unkeyed.
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Re: Artificial centre tap for GG 3CX1200
On Fri, Dec 1, 2023 at 11:58 AM, Chuck Neal wrote:
Yes I have done this and it works very well.
Ahh that's good to hear, Thanks! Any idea on whats needed of the required transformer? I'm kind of thinking that as long as the winding can handle the DC current, and doesn't have a huge DC resistance, then it's probably ok? Like a 12V 1A maybe? I'll poke around and see how easy it would be to add a CT, didn't really consider that at first, but yeah. Thanks Guys.
|
Got an 80B here and I am having meter issues. The swr and power meter were not working properly and I put in a new op amp on the meter board and I also changed out the 2 2n3904's going to the op amp.
Now the meters are at full scale. At this point its over my head. Was wondering if anyone had any ideas.? The grid and plate meter is fine and the amp puts out bear a KW. I am just using me external meter for the time being.
Tia
Dave N8DC
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Re: Need Help with Amp Supply LK500ZC
Adrian and all
I measured the voltage across what I believe to be R6 in the 1988 power supply schematic or R1 in the 1983 schematic.? It is visible in the 4th picture I sent yesterday evening (PST) in the upper right corner of the 4th picture down as a large 100k resistor attached to the large zener diode.
? I hooked up my tranceiver output to the dummy load but left the relay connected to the amplifier and keyed and unkeyed the transceiver in RTTY mode.? Amp in XMT mode.?? Transmitter unkeyed, the voltage across the resistor was around 44.5 volts.?? Keyed, the voltage was a few millivolts.??
Someone asked about idling current.? With no drive but the amp keyed I'm seeing about 80 ma? plate current and about 30 ma grid current.? Both meters drop to 0 when unkeyed.
XYL insists I clear the 300 foot driveway of the foot of snow that fell last night so I'll be away for the next few hours.
/John
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Re: Artificial centre tap for GG 3CX1200
Quote: “I've also heard of using the secondary winding of a totally separate transformer that does have a CT, and using it in parallel across my filament winding, then using that transformers centre tap.” ? Yes I have done this and it works very well.? Using the resistors for a fake CT will add a variable bias as the cathode current varies which will hurt the IMD performance.? Also as suggested, you might be able to make your own CT.? Try probing the secondary winding with a DVM fitted with a pin to see if you can find the ? voltage point.? I have also done this and found a CT at a very easy point to get to between the two layers of the secondary at the physical end between the two layers. ? -Chuck K1KW
?
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From: ham-amplifiers@groups.io [mailto:ham-amplifiers@groups.io] On Behalf Of va3dxv
Sent: Friday, December 01, 2023 1:57 PM
To: ham-amplifiers@groups.io
Subject: [ham-amplifiers] Artificial centre tap for GG 3CX1200 ? Hi, I've been trying to gather parts for a 3CX1200D7 build. I had trouble locating a sufficient filament transformer. Tube requires 6.3V @ 25A. Ended up finding one for 6.3V @ 28A - Would like to have more overhead but thought it would be the best I'd find, and only $50 brand new! Perfect!
BUT In my haste to complete an order of needed parts, I wasn't paying close enough attention. It turns out that it doesn't have a CT. (it's dual secondary - parallel is 6.3V@28A and series is 12.6V@14A) - D'oh!
Now what... when I used to play with guitar/audio amps, a semi-common thing to do would be to take a pair of low value resistors, put one end of each to each end of the filament winding, and ground the joint in the middle for a fake CT. Unsure how this will affect a cathode bias.
I've also heard of using the secondary winding of a totally separate transformer that does have a CT, and using it in parallel across my filament winding, then using that transformers centre tap. Further, I've heard of using a pair of diodes, each anode to each end of my filament winding and tie the cathodes together in the middle... or maybe that was t'other way around... either way I dunno about this either.
Anyways, obviously the best way forward would be to actually use a proper transformer, but since I can't find one and I already made this oopsie... I'm wondering what the next-best-way forward is? :)
Thanks :)
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Re: Artificial centre tap for GG 3CX1200
Still another easy way out is to unwind those heavy windings and
put in your own center tap. There can't be more than 20, 25 turns
of wire per 6V winding?? Transformer secondaries are always wound
on the outside, meaning modifying them is very easy.
Steve, K0XP
On 12/1/2023 10:56 AM, va3dxv wrote:
Hi, I've been trying to gather parts for a 3CX1200D7 build. I had
trouble locating a sufficient filament transformer. Tube requires
6.3V @ 25A. Ended up finding one for 6.3V @ 28A - Would like to
have more overhead but thought it would be the best I'd find, and
only $50 brand new! Perfect!
BUT In my haste to complete an order of needed parts, I wasn't
paying close enough attention. It turns out that it doesn't have a
CT. (it's dual secondary - parallel is 6.3V@28A and series is
12.6V@14A) - D'oh!
Now what... when I used to play with guitar/audio amps, a
semi-common thing to do would be to take a pair of low value
resistors, put one end of each to each end of the filament
winding, and ground the joint in the middle for a fake CT. Unsure
how this will affect a cathode bias.
I've also heard of using the secondary winding of a totally
separate transformer that does have a CT, and
using it in parallel across my filament winding, then using that
transformers centre tap. Further, I've heard of using a pair of
diodes, each anode to each end of my filament winding and tie the
cathodes together in the middle... or maybe that was t'other way
around... either way I dunno about this either.
Anyways, obviously the best way forward would be to actually use a
proper transformer, but since I can't find one and I already made
this oopsie... I'm wondering what the next-best-way forward is? :)
Thanks :)
--
See my QRZ.com page at
|
Artificial centre tap for GG 3CX1200
Hi, I've been trying to gather parts for a 3CX1200D7 build. I had trouble locating a sufficient filament transformer. Tube requires 6.3V @ 25A. Ended up finding one for 6.3V @ 28A - Would like to have more overhead but thought it would be the best I'd find, and only $50 brand new! Perfect!
BUT In my haste to complete an order of needed parts, I wasn't paying close enough attention. It turns out that it doesn't have a CT. (it's dual secondary - parallel is 6.3V@28A and series is 12.6V@14A) - D'oh!
Now what... when I used to play with guitar/audio amps, a semi-common thing to do would be to take a pair of low value resistors, put one end of each to each end of the filament winding, and ground the joint in the middle for a fake CT. Unsure how this will affect a cathode bias.
I've also heard of using the secondary winding of a totally separate transformer that does have a CT, and using it in parallel across my filament winding, then using that transformers centre tap. Further, I've heard of using a pair of diodes, each anode to each end of my filament winding and tie the cathodes together in the middle... or maybe that was t'other way around... either way I dunno about this either.
Anyways, obviously the best way forward would be to actually use a proper transformer, but since I can't find one and I already made this oopsie... I'm wondering what the next-best-way forward is? :)
Thanks :)
|
Re: Need Help with Amp Supply LK500ZC
One picture clearly shows the the CT bias resistor and the zener diode being switched by a relay (blue)mounted on the center wall. ?The PC board which looks like a relocation of the ALO board might be doing some detecting of swr or something that might shut down??the ptt? or something. ?Bug it sure doesn’t look transistor bias switching with the wiring I see over to the blue relay. He’s got a radio Dan?gizmo with a coax going onto it. ?I’m wondering if that senses RF and triggers the relay PTT line, ? This is definitely one for my memoirs. ?Just when you thought you’ve seen it all something comes along and takes the cake. ?Engineers build?amplifiers and hams cone along and try to make it better. I could fill up a 55 gallon drum of modifications I ripped out of amps. ?With no documentation it gets costly to spend the time to figure out what some?? screwdriver happy ham had in his brain. Jeez
On Friday, December 1, 2023, 12:39 AM, John Roland <johnroland51@...> wrote:
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Re: Need Help with Amp Supply LK500ZC
What I think Lou is saying is...... the cut off bias isn't being applied on RX....( cuz of lousy bias relay contacts on RX)...... hence the tubeS are sucking normal idle current.? BUT if that was the case, the plate current meter would be indicating normal idle current.? ?Now that the amp seems to be functioning ok...... what is the normal idle current ????? (keyed, but NO drive applied).?
?
With normal idle current, how much idle current is there...and what is the loaded B+?? ?Knowing that, simple calc to determine idle anode dissipation.?
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Re: Need Help with Amp Supply LK500ZC
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Re: Need Help with Amp Supply LK500ZC
Another thing not to be overlooked which is prevalent in many Ameritron amps is a shorted bypass cap on the bias line anywhere along it’s length?.??In rare cases, but possible,?a bypass cap that’s shorted on the filament choke can cause such issues. ?If ?shorted?however in the second test he did it seemed like the tubes behaved which would rule out a short and point to something intermittent like a moving contact perhaps.
On Thursday, November 30, 2023, 9:21 PM, Louis Parascondola via groups.io <Gudguyham@...> wrote:
Not all LK500 amps had QSK and vacuum relay output, it was an option. ?Some had a standard 3PDT relay like an SB220 et Al. ?Even if your amp has a QSK option it’s not working and the previous owner did a CF modification as is clearly shown by those outboard coaxial relays. ?That?said whoever did that probably has a third relay inside the amp for bias switching. ?REGARDLESS OF HAVING THE QSK OPTION OR NOT, THE BIAS SWITCHING IS NOT DONE DIRECTLY WITH ANT TRANSISTOR, THE BIAS IS STILL RELAY SWITCHED WITH CONTACTS IN EITHER?CASE. ?Don’t get bogged down with a bad transistor. ?Now that we know this amp has had the golden screwdriver done to it, it’s time to pop the top and show a photo of the rest area so we can see how the “ tinker” handled the bias switching. Sent from the all new AOL app for iOS
On Thursday, November 30, 2023, 7:44 PM, Adrian Fewster <vk4tux@...> wrote:
The comments about a bad bias contact do not make sense to me ;
If K1C contact was welded (closed #) , which is highly unlikely
in such a low current circuit unless a fault current came through,
then that may be a possibility.
The issue was in standby , with relay open. If K1C is open and
not #; R1 (I requested check in earlier post) would need to be
shorted as that provides resistor bias cutoff.
D3 would probably need to be defective as well. The meters seems
to work so plate current should be checked on TX with and without
drive to check bias current? ?
73
vk4tux
On 1/12/23 09:46, Dave w6de wrote:
There
are burnishing tools for exactly this purpose.?
Using finger nail files and files for this purpose is
risky, as the potential damage of removing too much contact
material is high.
?
I
have one of these:
Here
are two more:
?
?
Burnishing
tools have very fine almost invisible teeth.?
Using a burnishing tool is a safe method for cleaning
relay contacts.?
Every radio amateur that works on equipment with open
frame relays should have one in his tool kit.
?
73,
Dave,
w6de
?
?
John,
you just might have a worn out contact that switches bias on
the antenna relay. ?If the contacts are severely pitted they
might not make up too good sometimes and other times ok.
?You need to inspect the that set of contacts in particular.
?If you carefully remove the rear spring on the relay you
can lift the armature off and inspect all the contacts. ?The
contacts that switch the RF can be cleaned gently, the
contacts on the bias may be in bad shape, there may be a
tiny point on the armature contact and a tiny depression on
the body contact. A gentle filing to remove the “pit” and a
cleaning should restore reliable contact. ?It’s not unusual
at all to see the bias contact hood bad with the age of thst
amp especially being used on CW a lot. ?Seen it quit often
and by doctoring up the bias?contact that problem went away.
?Lou
Sent from
the all new AOL app for iOS
?
On Thursday, November
30, 2023, 3:58 PM, John Roland <johnroland51@...> wrote:
|
Re: Need Help with Amp Supply LK500ZC
Running any kind of paper currency or?business card or the like will only help the RF rx side of the switch contacts which are the NC contacts. ?NO or NC contacts on the??armature contacts C on the bias can develop a “ pit” and “tit” scenario on the contacts. ?They can not be clean with any miracle spray goop of paper treatment. ?A mild file is needed to fix up those contacts and followed with a buffing. ?If done correctly contact surface can be?successfully?restored. ?The contact flashing isn’t?needed so much on the bias contacts as it is needed on the NC contacts in the receive path! ?Dentron amps are specifically?prone to the issue. ?I’ve had to restore damaged bias contacts several times before.
On Thursday, November 30, 2023, 7:18 PM, Steve <k0xp@...> wrote:
Very often, all that is necessary is to run a bizness card
between the contacts. A card with a particularly-rough finish is
great, but don't use a card with an epoxied smooth or glossy
finish on one side. If you do, then try to stick a sheet of
ordinary notebook paper to that side of the card so it doesn't
contact the relay contacts. The epoxy or gloss may rub off onto
the relay contact and make the problem even worse.
When you run a bizness card thruogh the contacts and examine it,
you will notice gray or black residue is left on the card.
However, the card will not clean up a burned or pitted contact
very well.
73,
Steve K0XP
On 11/30/2023 3:46 PM, Dave w6de wrote:
There
are burnishing tools for exactly this purpose.?
Using finger nail files and files for this purpose is
risky, as the potential damage of removing too much contact
material is high.
?
I
have one of these:
Here
are two more:
?
?
Burnishing
tools have very fine almost invisible teeth.?
Using a burnishing tool is a safe method for cleaning
relay contacts.?
Every radio amateur that works on equipment with open
frame relays should have one in his tool kit.
?
73,
Dave,
w6de
?
?
John,
you just might have a worn out contact that switches bias on
the antenna relay. ?If the contacts are severely pitted they
might not make up too good sometimes and other times ok.
?You need to inspect the that set of contacts in particular.
?If you carefully remove the rear spring on the relay you
can lift the armature off and inspect all the contacts. ?The
contacts that switch the RF can be cleaned gently, the
contacts on the bias may be in bad shape, there may be a
tiny point on the armature contact and a tiny depression on
the body contact. A gentle filing to remove the “pit” and a
cleaning should restore reliable contact. ?It’s not unusual
at all to see the bias contact hood bad with the age of thst
amp especially being used on CW a lot. ?Seen it quit often
and by doctoring up the bias?contact that problem went away.
?Lou
Sent from
the all new AOL app for iOS
?
On Thursday, November
30, 2023, 3:58 PM, John Roland <johnroland51@...> wrote:
--
See my QRZ.com page at
|
Re: Need Help with Amp Supply LK500ZC
Not all LK500 amps had QSK and vacuum relay output, it was an option. ?Some had a standard 3PDT relay like an SB220 et Al. ?Even if your amp has a QSK option it’s not working and the previous owner did a CF modification as is clearly shown by those outboard coaxial relays. ?That?said whoever did that probably has a third relay inside the amp for bias switching. ?REGARDLESS OF HAVING THE QSK OPTION OR NOT, THE BIAS SWITCHING IS NOT DONE DIRECTLY WITH ANT TRANSISTOR, THE BIAS IS STILL RELAY SWITCHED WITH CONTACTS IN EITHER?CASE. ?Don’t get bogged down with a bad transistor. ?Now that we know this amp has had the golden screwdriver done to it, it’s time to pop the top and show a photo of the rest area so we can see how the “ tinker” handled the bias switching.
On Thursday, November 30, 2023, 7:44 PM, Adrian Fewster <vk4tux@...> wrote:
The comments about a bad bias contact do not make sense to me ;
If K1C contact was welded (closed #) , which is highly unlikely
in such a low current circuit unless a fault current came through,
then that may be a possibility.
The issue was in standby , with relay open. If K1C is open and
not #; R1 (I requested check in earlier post) would need to be
shorted as that provides resistor bias cutoff.
D3 would probably need to be defective as well. The meters seems
to work so plate current should be checked on TX with and without
drive to check bias current? ?
73
vk4tux
On 1/12/23 09:46, Dave w6de wrote:
There
are burnishing tools for exactly this purpose.?
Using finger nail files and files for this purpose is
risky, as the potential damage of removing too much contact
material is high.
?
I
have one of these:
Here
are two more:
?
?
Burnishing
tools have very fine almost invisible teeth.?
Using a burnishing tool is a safe method for cleaning
relay contacts.?
Every radio amateur that works on equipment with open
frame relays should have one in his tool kit.
?
73,
Dave,
w6de
?
?
John,
you just might have a worn out contact that switches bias on
the antenna relay. ?If the contacts are severely pitted they
might not make up too good sometimes and other times ok.
?You need to inspect the that set of contacts in particular.
?If you carefully remove the rear spring on the relay you
can lift the armature off and inspect all the contacts. ?The
contacts that switch the RF can be cleaned gently, the
contacts on the bias may be in bad shape, there may be a
tiny point on the armature contact and a tiny depression on
the body contact. A gentle filing to remove the “pit” and a
cleaning should restore reliable contact. ?It’s not unusual
at all to see the bias contact hood bad with the age of thst
amp especially being used on CW a lot. ?Seen it quit often
and by doctoring up the bias?contact that problem went away.
?Lou
Sent from
the all new AOL app for iOS
?
On Thursday, November
30, 2023, 3:58 PM, John Roland <johnroland51@...> wrote:
|
Re: Need Help with Amp Supply LK500ZC
Here's the photo of the relays that I tried to attach to my last post.
|
Re: Need Help with Amp Supply LK500ZC
Steve, Dave, Lou, and allOne of my problems is that I'm doubtful that I have a complete schematic for this amplifier.?? Best I've been able to find is from a 1988 users manual I found? . The previous owner who refurbished the amp replaced what I believe is the relay you refer to with what I was told are high-end vacuum relays, which if so, I wouldn't expect to be the problem and if it is, I wouldn't think burnishing contacts would be feasible. I'm also not understanding on how a bad relay would relate to the overheating when the amp was idling??
I have on my to-do list the task of reconciling the schematic with the existing circuitry, which is not something I feel I'm very good at.? I was told the QSK circuitry was bypassed (removed?) ("They're nothing but trouble")? and I've never seen the ALO light come on so not sure it hasn't also been disabled.? Other questions I have about the amp are whether it is good on the WARC bands and how to tell if it has a soft-start circuit which I read somewhere were factory installed on later models but I don't recognize in the schematic I have.
And to clarify my earlier post, the tubes were refitted not replaced.? Thanks Adrian.
Cheers for now.
/John
|
Re: Need Help with Amp Supply LK500ZC
Very often, all that is necessary is to run a bizness card
between the contacts. A card with a particularly-rough finish is
great, but don't use a card with an epoxied smooth or glossy
finish on one side. If you do, then try to stick a sheet of
ordinary notebook paper to that side of the card so it doesn't
contact the relay contacts. The epoxy or gloss may rub off onto
the relay contact and make the problem even worse.
When you run a bizness card thruogh the contacts and examine it,
you will notice gray or black residue is left on the card.
However, the card will not clean up a burned or pitted contact
very well.
73,
Steve K0XP
On 11/30/2023 3:46 PM, Dave w6de wrote:
There
are burnishing tools for exactly this purpose.?
Using finger nail files and files for this purpose is
risky, as the potential damage of removing too much contact
material is high.
?
I
have one of these:
Here
are two more:
?
?
Burnishing
tools have very fine almost invisible teeth.?
Using a burnishing tool is a safe method for cleaning
relay contacts.?
Every radio amateur that works on equipment with open
frame relays should have one in his tool kit.
?
73,
Dave,
w6de
?
?
John,
you just might have a worn out contact that switches bias on
the antenna relay. ?If the contacts are severely pitted they
might not make up too good sometimes and other times ok.
?You need to inspect the that set of contacts in particular.
?If you carefully remove the rear spring on the relay you
can lift the armature off and inspect all the contacts. ?The
contacts that switch the RF can be cleaned gently, the
contacts on the bias may be in bad shape, there may be a
tiny point on the armature contact and a tiny depression on
the body contact. A gentle filing to remove the “pit” and a
cleaning should restore reliable contact. ?It’s not unusual
at all to see the bias contact hood bad with the age of thst
amp especially being used on CW a lot. ?Seen it quit often
and by doctoring up the bias?contact that problem went away.
?Lou
?
On Thursday, November
30, 2023, 3:58 PM, John Roland <johnroland51@...> wrote:
--
See my QRZ.com page at
|
Re: Need Help with Amp Supply LK500ZC
There are burnishing tools for exactly this purpose.?
Using finger nail files and files for this purpose is risky, as the potential damage of removing too much contact material is high.
?
I have one of these:
Here are two more:
?
?
Burnishing tools have very fine almost invisible teeth.?
Using a burnishing tool is a safe method for cleaning relay contacts.?
Every radio amateur that works on equipment with open frame relays should have one in his tool kit.
?
73,
Dave, w6de
?
toggle quoted message
Show quoted text
From: ham-amplifiers@groups.io <ham-amplifiers@groups.io>
On Behalf Of Louis Parascondola via groups.io
Sent: 30 November, 2023 22:56
To: ham-amplifiers@groups.io
Subject: Re: [ham-amplifiers] Need Help with Amp Supply LK500ZC
?
John, you just might have a worn out contact that switches bias on the antenna relay. ?If the contacts are severely pitted they might not make up too good
sometimes and other times ok. ?You need to inspect the that set of contacts in particular. ?If you carefully remove the rear spring on the relay you can lift the armature off and inspect all the contacts. ?The contacts that switch the RF can be cleaned gently,
the contacts on the bias may be in bad shape, there may be a tiny point on the armature contact and a tiny depression on the body contact. A gentle filing to remove the “pit” and a cleaning should restore reliable contact. ?It’s not unusual at all to see the
bias contact hood bad with the age of thst amp especially being used on CW a lot. ?Seen it quit often and by doctoring up the bias?contact that problem went away. ?Lou
?
On Thursday, November 30, 2023, 3:58 PM, John Roland <johnroland51@...>
wrote:
|
Re: Need Help with Amp Supply LK500ZC
John, you just might have a worn out contact that switches bias on the antenna relay. ?If the contacts are severely pitted they might not make up too good sometimes and other times ok. ?You need to inspect the that set of contacts in particular. ?If you carefully remove the rear spring on the relay you can lift the armature off and inspect all the contacts. ?The contacts that switch the RF can be cleaned gently, the contacts on the bias may be in bad shape, there may be a tiny point on the armature contact and a tiny depression on the body contact. A gentle filing to remove the “pit” and a cleaning should restore reliable contact. ?It’s not unusual at all to see the bias contact hood bad with the age of thst amp especially being used on CW a lot. ?Seen it quit often and by doctoring up the bias? contact that problem went away. ?Lou
On Thursday, November 30, 2023, 3:58 PM, John Roland <johnroland51@...> wrote: Lou, Mike, Jim, Adrian and all, I removed the tubes one at a time.? I let the amp idle (no drive) for 10 minutes with each tube in place individually.?? No signs of anything overheating.? I then replaced both tubes and let it set another 10 minutes, still no sign of overheating.?? I then applied about 20 watts of drive in RTTY mode and was getting around 200 watts out.? (I'm still using my Heathkit watt meter circa 1978)? Attached is a photo of my grid and plate current with that 20 watt drive.? The meter shows 2900 volts when idling and drops to about 2600 when transmitting.?? (I'm operating 240 volts on about a 20 foot length of 12 AWG from the panel.)? The pictures below are 1.? the front tube at 10 minutes.? 2. the rear tube at 10 minutes? 3. Both tubes back in place after 10 minutes.? 4.? A picture from yesterday of both tubes just after switching off the power (light) which looks to me like both tubes are overheated. 5.? A picture of my meters with 20 watts RTTY drive applied.? The Plate volt meter does return to 0 when switched off. So it now looks like I may have some kind of an intermittent ?? Thanks again /John? W7SWB     
|
HaL Mandel