Quote from: Amestech on June 20, 2023, 09:35:50 PM

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.

You want to measure from the transistor collectors (case) to the metal of the heatsink.
If the transistor is not shorted from emitter to collector, a low resistance reading will indicate the collector to heatsink insulator is not good.

#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.

The sarcasm and derision was not directed at your request at all, rather the amp marketing.
At it's price point, I can't see the schematic ever becoming available.  I would think if they are servicing under warranty at all, it would be board swap.  But most likely, during warranty the whole amps are replaced, like amps on the Fender 'do not repair' list.

For parts, their support page says: 'Replacement parts are not currently offered for our amplifiers'.

All that being said, I do see a service manual for the Acoustic Control B600 at electrotanya, so maybe schematics are available to official service centers, if there are any (service centers).

Are you wanting to switch 'on the fly'?
Then you might be concerned about whether the switch is 'make before break' or 'break before make'.
A 'make before break' type switch might allow parallel speaker combinations during switchover, which could allow too low a load impedance, or trigger protection circuits.

Other than that I don't see any issues, like joecool85 said above, solid-state amps are fine when there is no load.

Short answer is no, you can't do it that way.
This model has 128 programmable patches. So you need to make your 6 patches (or however many you want), set the volume for each patch, save them, and switch between them.
You need the exact footswitch (FS-10) to do that.

Q4 was the correct part to remove in order to disable the noise gate.
Glad you got it sounding better.
Q4 would not test like a usual transistor as it is a FET.  It must have been turning on as the noise-gate was doing something.

Did you ever try the octave feature to see if it is working?  That is the only other thing I can think of that might be dragging down the +14V line.  U8 and U12 are for the octave circuit, I was mistaken when I earlier said they were for the noise gate/limiter.

Zener D19 is up alongside R45, while D18 is beside R82.
R45 runs hotter, so that may be why D19 is hotter.

See post #7 about 15VX supplies.

Is there much difference in voltage across R45 when ch.2 is selected compared to ch.1?
What is the voltage across R86 (to tuner) ?

layout diagram attached
You cannot view this attachment.

Maybe it is Q4 that is responsible for Q5 source drop-out.
Looks like a limiter circuit consisting of Q4,Q5, U8 and U12.
Also, U8 and U12 are the only things running off 15VX (via R82), so maybe one of those IC's could also be responsible for the +15V rail issue.  Do either feel hot?
(edit: that would be the noise gate circuit that tassieviking mentioned, not a limiter)

Can you post the correct schematic for your unit?
Otherwise there is no way to tell what TP1 is.

Off the top of my head I would say to go with the lower reading for both channels, unless you see crossover distortion.

Did you verify the resistance of R42 and check it's solder joints?

Also, charity type thrift stores or youth drop-in centres would probably appreciate it.

That reminds me what Enzo used to always say, 'a tube tester can only tell you a tube is bad'.  I think that applies to most test equipment, and not just for tubes.
You can measure a part and find out it's either bad, or 'may be good'.
Real testing in actual use will tell you if it really is good in it's end application.

When you reverse that speaker that has wrong polarity, you should notice better bottom end/bass response.

Quote from: saturated on May 02, 2023, 10:55:03 AMI have read that yellow and red are pos
and blue and black are neg...
but i can not find any markings on the speakers or terminal

You are correct, that is the colour coding Peavey uses.  The red dots on the speaker baskets are the + terminal.  (that means one spkr in pic is wired wrong polarity)

I have a '77 K15 GMC, also with 4 spd.
The hood is in the same condition as yours, that's why it caught my eye.