Butcher MKII 120V switching issue

[jduma]

I don't know what happened to my other post. I got a Peavey Butcher MKII on the bench which is unable to switch anything on the front. I did some logic probing and it seems like the main program IC U12. Green is low logic and red is high logic, some pins respond to the front panel switching, red and green. There is also some pins that have intermediate voltage, red and green connected. Seems like the easiest thing is to replace the programmed IC, but maybe others have suggestions. Also what a great amp design I feel like this is a sleeper.

Thanks,

Justin D.

[guitarman59]

I have 2 and they are great amps. Definitely sleepers The master 1 and 2 LEDS dont work on the front panel. Any ideas??

I want to put a choke on one of them also. I assume removing R85??

Peavey cant tell me what the bias voltage is at the test point either.

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[guitarman59]

These really sound great with EHX 12ax7's in the PI slot. Im pretty sure the one that hasnt been touched shipped from Peavey with that tube in there.

[rogue777]

Is this the right manual? You guys must know more about this than I do.

https://www.americanmusical.com/itemfil ... manual.pdf

This manual implies the Master Volume 1 and 2 leds are controlled by the footswitch (which is a MIDI controller) or an external MIDI controller. You must use the 8-pin cable with the footswitch. The manual has MIDI info on pg 15. I would not replace U12 without testing using a MIDI controller.

[guitarman59]

Is this the right manual? You guys must know more about this than I do.

https://www.americanmusical.com/itemfil ... manual.pdf

This manual implies the Master Volume 1 and 2 leds are controlled by the footswitch (which is a MIDI controller) or an external MIDI controller. You must use the 8-pin cable with the footswitch. The manual has MIDI info on pg 15. I would not replace U12 without testing using a MIDI controller.

Yes thats the correct manual. I have 2 Peavey footswitches and cables that came with the amps as I have 2 Butcher Heads.

Amp One amp functions correctly,

Amp Two has all the functions Except the Master 1&2 LEDS do not light up at all with either switch or cables.

The Master volumes work correctly and the LEDS on both switches show the Master1&2 selected just nothing on the amp face.

Im not sure you can program the LEDS but I may be mistaken.

[rogue777]

Guitarman59, thanks for the reply. That’s good you have the two amps to compare them both. By selecting Master Volume 1 or 2 with the footswitch you are in effect controlling or programing the selected LED to light. Thanks for the pictures.

If you can use a DVM and make voltage readings with the amp pwr on, select a MV Led to “turn-on”. Record the voltage on each pin of the LED, measuring from the backside of the front panel bd. So don’t take things apart. An LED might need 1.8 V to 3.3 VDC across it to light. I’m assuming it’s a DC voltage.
The failure could be a power supply, or the LED itself, or the driver that causes the LED to turn-on/off. Reset or check those push-on gray connection cables that connect from the main bd to the front panel bd are making good contact, Specifically anyone that would be associated with the MV Led control signals or pwr supply. I’d think the LEDs are soldered in and not in sockets. You might need a schematic.
If the bad-amp LEDs don’t make any sense why they’re not working, you could take voltage measurements on the good amp, then check the bad amp to see where the discrepancy is. That would show where the problem is.

[rogue777]

Are you sure the lights are LED's? They could be little lamps and the filaments are open.

On one of the pictures - the back of the front panel bd has like little antenna leads sticking out. Those look like lamp leads. Also the voltage that makes it light could be an AC voltage. If they are lamps, with the pwr off measure the ohms of the filaments, to test.

[guitarman59]

Are you sure the lights are LED's? They could be little lamps and the filaments are open.

On one of the pictures - the back of the front panel bd has like little antenna leads sticking out. Those look like lamp leads. Also the voltage that makes it light could be an AC voltage. If they are lamps, with the pwr off measure the ohms of the filaments, to test.

Pretty sure they are LEDS but will have a look today and pull the small board out if necessary.