Posted: 5/2/2026 4:21:39 PM EDT
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Fixed the meter protection diode. Now I'm getting the proper meter movements per Tom W8JI instructions. Can hear the relay click and get a red transmit light. Running bypassed my swr meter reads normal power level. Switch to OPR and there is no transmit power. Tom's website says to remove one tube at a time to test for a bad tube. Good place to start? What else? |
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Transmitting into a 1.5KW dummy load. Have over 1.5KV HV current. Pic below of attempting tuning. Attached File |
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Well shit, there are 2 different types of tubes in here. Two in the radio matched and the other one matched the 2 extra tubes that came with the radio. Tried the 2 extra tubes so that all 3 matched and still nothing. Thinking I got someone's mess. Pictures of the 2 different tubes. The first 2 have a mirror coating and small circular protrusion and the others do not.Attached File Attached File Attached File Attached File |
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Better pictures of all 5 tubes that came with the amp. Attached File Attached File Attached File Attached File |
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Originally Posted By AnalogKid: How good are your troubleshooting skills? I see a couple potential areas on the schematic to check for signs of problems if you have the required test gear. I have a fluke 600 volt meter and can measure voltage and continuity. Resistance would be new to me. My big problem is a tremor. It's not evident until I grab a soldering iron and try to hold it still. 😅 |
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Originally Posted By Ramcharger_pilot: I have a fluke 600 volt meter and can measure voltage and continuity. Resistance would be new to me. My big problem is a tremor. It's not evident until I grab a soldering iron and try to hold it still. 😅 If you want an opinion, I will give one. Your first troubleshooting job should not be a "death machine" like this amplifier. I would HIGHLY suggest you take it to someone that has some skill at working on tube type amps. Just my 2 cents and you can take that for what you paid for it. Good luck and 73 James, K0UA |
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| I had one of these amps (the 4 tube H model) and yes I had problems with it and was able to repair it each time. BUT I had over 50 years of electronic troubleshooting experience under my belt before I ever saw it. Including working on tube equipment with lethal voltages. And my hands don't shake. |
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OP the Tulsa Amateur Radio Club (W5IAS): This is the primary club for your area. They host a dedicated "Ask an Elmer" session and a Tech Night on the first Tuesday of every month at the University of Tulsa (Keplinger Hall). This might be the best place to find a local expert who can safely assist you with tube amp diagnostics. https://w5ias.com/meetings/ |
“Every man has two deaths, when he is buried in the ground and the last time someone says his name. In some ways, men can be immortal. “ - Ernest Hemingway
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Thanks everyone. I agree a "death machine" is not where to start. I had a membership to the Tulsa club last year but didn't get any correspondence. Signed up at the local hamfest and paperwork may have been lost. Was just looking at the website and will contact them. Thanks again everyone. Tremors suck. It's not usually noticeable except for holding something long, like a soldering iron or shooting benchrest. |
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Will wait for an AAR from OP after he gets help with the unit, but given the fact that idling current is present when the amp is switched into transmit I tend to think that part of the T/R changeover relay plus filament and HV supplies are in order. This leads me to three possibilities, especially if no output is present on ANY band: One, RY1 - the relay which switches drive energy into the input filters. Two, S1A - the rotary switch which selects the proper input filter for a given band. Three, the filament blocking capacitor which couples drive power from the input filter section to the filament line. My SWAG is S1A. OP, you said this amp is an unknown quantity. Methinks someone may have been mucking around that section and possibly mis-timed it. |
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Originally Posted By AnalogKid: Will wait for an AAR from OP after he gets help with the unit, but given the fact that idling current is present when the amp is switched into transmit I tend to think that part of the T/R changeover relay plus filament and HV supplies are in order. This leads me to three possibilities, especially if no output is present on ANY band: One, RY1 - the relay which switches drive energy into the input filters. Two, S1A - the rotary switch which selects the proper input filter for a given band. Three, the filament blocking capacitor which couples drive power from the input filter section to the filament line. My SWAG is S1A. OP, you said this amp is an unknown quantity. Methinks someone may have been mucking around that section and possibly mis-timed it. One of the many problems I had withe amp was The Relay. I replaced it but it was a PITA to take everything apart to get to and was a major pain to unsolder. Of course the diode problem which failed several times until I replaced it with a 3 amp diode. And I was VERY careful to get the switch timing set back up correctly. I made alignment marks to re assemble it. In my opinion the entire amp was a pain to work on and like I said, I have a lot of experience working on things that are a PITA. |
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Originally Posted By Ramcharger_pilot: 2 or 3 and 0 grid. Plate setting 7.5 Load setting 4.5 'HV / IP switch in iP, iP should read zero not keyed, just checking the meter zero point. With the amp keyed and no drive power, you should read 110 ma on the bottom of the meter. You are reading 2 or 3 so you have basically zero plate current. Could easily be a bad tube or 2. With drive you have plate current but no output. Also sounds like a bad tube or 2. Those 2 tubes with black on the inside don't look so good. |
Mach
Nobody is coming to save us.
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Nobody is coming to save us.
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Originally Posted By Frank_B: The reflective coating is from the getter being "flashed". I don't see any evidence of the clear tubes even having a getter. The clear tubes don't appear to have one. The Tulsa amateur radio club president emailed and recommended an amp repair person a couple of hours away. I'll give him a call. Thanks. |
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Originally Posted By Ramcharger_pilot: The clear tubes don't appear to have one. The Tulsa amateur radio club president emailed and recommended an amp repair person a couple of hours away. I'll give him a call. Thanks. Hopefully you will get this sorted out in short order. |
“Every man has two deaths, when he is buried in the ground and the last time someone says his name. In some ways, men can be immortal. “ - Ernest Hemingway