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  1. This amp is getting to be like a bad penny. I...

    This amp is getting to be like a bad penny. I gave up, put the whole thing back together, powered back up to give a listen, assuming all still worked. I hadn't yet mounted the rear fan panel, so I...
  2. The Super Bassman is using Pin 8 for their...

    The Super Bassman is using Pin 8 for their Cathode connection. I'll have to look to see if Pin 1 is used for anything.

    After I posted my new findings yesterday afternoon, I found after putting in...
  3. New Findings! I took the previous pulled Sovtek...

    New Findings! I took the previous pulled Sovtek 6550 power tubes from the amp, less the one that failed (frosty white inside the bottle), and it's partner from V7/V8 positions, and installed those...
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    Ah, I remember this oscillator. That was my...

    Ah, I remember this oscillator. That was my first oscillator as I began building up a lab back in the mid-70's. I was working for BGW Systems at the time, and we had bought a number of these kits,...
  5. My last venture back into the chassis was going...

    My last venture back into the chassis was going thru and reseating ALL of the interconnects, including the power tube PCB side of the ribbon cable from the Autobias PCB mounted to the inside surface...
  6. I've removed the Auto-Bias PCB V1.3 PCB from the...

    I've removed the Auto-Bias PCB V1.3 PCB from the inside rear panel of the chassis and installed the V1.2 PCB I had tucked away. Hardest part of changing that board out is getting the tiny flexible...
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    Having been using surgical headlights for years,...

    Having been using surgical headlights for years, with their 150W 21V Tungsten Halogen lamp inside the lamp supply, and always having the inconvenience of the fiber optic cable attaching me to the...
  8. Fender Super Bassman Auto-Bias Circuit Issue

    I have a Fender Super Bassman on the bench which had one failed Sovtek 6550 in itís output tube set. Having exhausted my Sovtek 6550 spare pulls on hand, I ordered a fresh matched Sextet of J/J...
  9. The tube is still in my local trash box at the...

    The tube is still in my local trash box at the end of the bench, though will I be able to identify it from the others recently tossed in.....remains to be seen. I'll have a look. Thanks for the...
  10. Odd fault found an a Fender Hot Rod Deluxe

    This morning, having restored the mod's to the Drive/More Drive circuit on a client's new Hot Rod Deluxe amp, while also scraping off all the solder mask on the original size solder pads for the...
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    As you're using the light bulb limiter, I gather...

    As you're using the light bulb limiter, I gather you're not equipped with a Variac and a power analyzer (or you would have been using them all along). What you CAN do, which seems like you're...
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    Is this occurring on BOTH the LF and HF amps? Or...

    Is this occurring on BOTH the LF and HF amps? Or just on the LF amp. Apart from the power supply levels, the basic circuit topology of the two amps is VERY similar. AND......the 0.375V reading...
  13. I must have missed it when you posted this. ...

    I must have missed it when you posted this. THAT's the way to put sense into all of these Marshall amps with the cajillion jumper cables! Excellent drawing!

    Any chance you also have one for the...
  14. Marshall TSL-100/122 Amp Head Interconnect Cables List attached

    I have a client's Marshall TLS-100 Amp Head in with crackling. Initial findings were not even getting output signal, or just barely....only leakage, so I was well past looking for the mentioned...
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    Ah, another use for my collection of stainless...

    Ah, another use for my collection of stainless steel & glass syringes that I bought years ago when you COULD buy such things on ebay without a medical purchase agent license. Haven't tried that...
  16. Also inside the power supply 'doghouse', you'll...

    Also inside the power supply 'doghouse', you'll find date codes on those large electrolytic caps. On some removed Mallory parts from that area, I read 7937D and 8038A. This translates to 1979, 37th...
  17. Marshall JCM 2000 DC fault between V2A plate and V3B grid

    After pulling the rear panel PCB off this Marshall JCM 2000 to inspect, find and repair the traditional solder joint fractures of the Impedance Select Switch, along with those on the output jacks, I...
  18. The Preamp boards in the SVT-CL are vastly...

    The Preamp boards in the SVT-CL are vastly different than the -CL. First, there are 2 channels. The Ch 1 is similar to the SVT-CL, though the mechanics are very different. 5 tubes total in the...
  19. Rear Fan Grill Panel floating

    Having had no success in getting that clicking noise to reappear, I put it back together this morning. As I was installing the rear fan grille panel, I noticed there's no assurance it gets grounded....
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    GK 800RB Power Amp PCB Parts Placement guide Rev C attached

    I ran that PCB Parts Placement guide thru my Acrobat Distiller, now this should appear. It always comes up in my computer, but, that's local. I didn't check the result yesterday after providing the...
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    Have you checked diodes D11, D12 (flyback diodes...

    Have you checked diodes D11, D12 (flyback diodes on the LF amp, D5, D6 (flyback diodes on the HF amp)? Also Limiter connect diodes D8 & D9 on LF amp, D2 & D3 limiter diodes on the HF amp, along with...
  22. Ampeg SVT-VR making clicking noises when first turned on

    One of my steady clients sent me an Ampeg SVT-VR which is(was) making clicking noises in the speaker when first turned on. They stated it may go away after 10 minutes or so. Yesterday, when I...
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    You're getting this 0.375V using your DMM's Diode...

    You're getting this 0.375V using your DMM's Diode Test Function (or Ohmmeter in the 2k range, which is a 2V source and 1mA constant current source), connected between base & collector, base &...
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    Probe Clips

    While I have a few Probe Master DMM probes, with the thread-on insulating tips to save your butt from being careless, I'm very fond of the XL EZ-Hook Mini-Probes, as seen in the first image connected...
  25. Glue applied to middle of long springs where they join together

    I kind of thought that was the area you were referring to. It was tight on both ends on the Ruby tank, while a tiny bit of play on the Accutronics tank.

    What I had done here, after touching the...
  26. I wasn't hearing anything that suggested random...

    I wasn't hearing anything that suggested random pops or crackling noises, plus got the same results with the new tank. I've removed the new tank, and, if you read my edited post from a few minutes...
  27. The Accutronics 4AB3C1B Reverb tank arrived, so I...

    The Accutronics 4AB3C1B Reverb tank arrived, so I moved an Eden WT-800 off the bench to see if this would be a quick slam-dunk. Would that it were so.

    The new tank howls just as badly as the Ruby...
  28. Having found a break in my maintenance schedule,...

    Having found a break in my maintenance schedule, I compiled a list in Excel listing everything I had purchased from Digi-Key, Mouser, Allied, Newark, CE Distribution between 2009 and 2014. I had...
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