Update. Ground issue solved. R150 popped. Missed that little piece of the schematic hiding in there.
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Show posts MenuQuote from: g1 on July 02, 2023, 01:58:51 PMPeavey uses several methods to connect circuit ground to chassis. Sometimes jacks, sometimes pot brackets, sometimes the screw posts touch a trace or wire jumper.
Partial or full disassembly of any unit can result in lost connections, it can be quite complex in some of the more modern stuff, for example some Yamaha mixers.
I guess there is a panel switch to select between clean/dirt channels and you want to toggle between lead and ultra? Then yes, grounding FS jack pin 2 will do so.
Quote from: Tassieviking on June 21, 2023, 10:57:22 AMIf you used thermal paste on the transistor insulators, make sure that you are using non-conducting paste.
It is very common to use conductive thermal paste in computers and other places where there is no need for any insulation between the component and the heatsink.
Thermal heatsink paste is a big no-no in amps, I refuse to have any at home just in case I make a mistake one day.
Good quality paste and just a very thin film of it is all you need, if you have the cheaper stuff it will dry up and become useless faster the the good stuff.
Quote from: DrGonz78 on June 21, 2023, 01:57:25 AMMy advice with Peavey designs that failed is to check every single little thing that resembles a diode. Those transistors count hugely but don't forget the 1N4148 diodes on the bias string for example. I am pretty compulsive with such a repair but I had issue with a peavey just like that. Thought I had checked everything but I missed one.
Quote from: g1 on June 21, 2023, 02:09:28 PMQuote from: Amestech on June 20, 2023, 09:35:50 PMYou want to measure from the transistor collectors (case) to the metal of the heatsink.Quote from: Tassieviking on June 20, 2023, 07:56:01 AMCould it be the TO-3 insulators, maybe you have a short from the power transistors to the heatsink.
... I couldn't tell with a multi since the emitter resistors are only .33ohms.
If the transistor is not shorted from emitter to collector, a low resistance reading will indicate the collector to heatsink insulator is not good.
Quote from: Tassieviking on June 20, 2023, 07:56:01 AMCould it be the TO-3 insulators, maybe you have a short from the power transistors to the heatsink.
Quote from: g1 on June 19, 2023, 08:27:52 PM#1 Do not connect any speaker or load until everything is working properly, all voltage correct.
If you had a speaker or load connected, recheck.
Secondly, it is not clear what you mean about disconnecting red wire of transformer. Please be more specific.
Lastly, this is a bit of an unconventional design, often called 'flying rails' where the normal spot we usually see the output is instead grounded. Where the center point of the pwr.amp supply is normally grounded, it instead goes to the speaker (+) terminal.
If you are not familiar with this type of design, it can be confusing.