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Peavey Mk IV Circuit diagram

#21
I have a four-button Peavey footswitch (right era, wrong model, probably from a guitar head) that switches between channels and combining channels (yes, these heads are designed to mix channels if desired). Automix is a weird feature I have never seen anywhere else, and I can imagine why, but that’s generally how I run mine ¯\_(ツ)_/¯
 
#22
You have signal at first startup on channel one.

So its likely the op amps are going high or low in this instance.

I didn't think it was a footswitch either cause its either grounded or its not. all that's happening.
So when engaged its probably doing its job.

Its the no amp signal description that got me confused. I imagined shutdown being triggered, but that cant really happen either. just a thermal breaker.

Possible its functioning as designed.

On start up it is Channel 1 on .
When the footswitch is engaged its turning off channel 1 channel 2 should be on.

In this case also possible Channel 2 is not getting turned on, but channel 1 is being turned off as designed.

There is no signal at all because channel 2 is not passing signal. And channel 1 is also off like its supposed to be.
So could be issue with Q4 the Fet that turns channel 2 signal on/off or U2B isnt turning on the Fet.

have to confirm voltages on U2 out pins/ and power pins, there is a led indicator it seems. if its lights up all good.
then confirm signal before and after the Fet/ and if it's gate voltage is changing.

I dont know what voltages the opamps are putting out at high/low or the current of the LEDS
but 1.5K dropping resisters seem little low, and if the LED is pulling 30 to 40 ma
thats close to max current id expect from a general purpose 4558
 
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#23
1.5k is 10mA so no problem there.

Without knowing what the foot switch does with the particular amp the op has, with an accurate schematic, it’s all just guessing. There may be nothing wrong with the amp itself.
 
#24
Riff Ranger said:
I have a four-button Peavey footswitch (right era, wrong model, probably from a guitar head) that switches between channels and combining channels (yes, these heads are designed to mix channels if desired). Automix is a weird feature I have never seen anywhere else, and I can imagine why, but that’s generally how I run mine ¯\_(ツ)_/¯
Click to expand...
With my Peavey Mark IV 400BH, that should say. Edits aren’t working right now.
 

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