Repair service [resolved]

At this point you'd want to focus on the small board not working properly.  You can even unplug the 6080 for now and just run the amp with the 12AU7.

Can you do a DC resistance check between terminal 1 and ground?

Generally when a C4S board fails to function, we see high voltage on the output and resoldering is required.  Seeing 0V on the output is more typical for the output being somehow shorted to ground, which suggests debris or wire ends touching as a cause of the problem.
 
Paul, it's incredible just how knowledgeable you are about virtually every single scenario concerning the circuit and troubleshooting. I mean I know you're a designer lol, but still... Hats off to you for all your help :)
 
Not to confuse the issue with facts, Your reply post #28 and #32 photos IMG4686 & IMG4687 Indicate that your amp is ON and your meter (looks like) it is set to ohms/resistance. If infact you are looking for a resistance reading the amp should not be ON. On the other hand if you are trying measure voltage then your meter is not set to the correct position.

Chris/AB2KH
 
PB is the expert here! and I agree you should focus on the small board at this point.

My amp has the old style boards so the connection identifiers are most likely different but the circuit I believe is the same. So hopefully you can follow by following the schematic.

The point at which the B+ connects to the the small board should be somewhere around 170 VDC (at least on my schematic) now if you measure the point at which the board connects to the plate of the 12AU7 you should see about 75VDC (at least on my schematic). You should be able to confirm these voltages from the working side of the board.

If you don't have 170 VDC on the in put you have a power supply issue.

If you don't have close to 75VDC on the plate of the 12AU7 then there is / are faulty components on that side of the board or a grounding issue between the cathode and ground. You did say it was working before speedball so that most likely is not a problem.

My money is on the 2907 being damaged either from incorrect installation initially or from heat damage during extraction and re insertion.

I hope this helps

PB you have the floor.

Chris/AB2KH
 
I am a bit concerned that I damaged the 2907 from the de and re soldering I did.

The legs got pretty hot in order to extract it. Is there anyway I can test directly whether or not that transistor is damaged?

I’m at work right now, but when I get home I can check these values and see if they’re around what’s expected.

This is my very first experience with any of this stuff, so I’m learning quite a bit all at once. It’s both exciting and frustrating.

I’ll let you know what I find tonight after work.
 
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