Dead MXR M87 Bass Compressor

[Alexi Bykovski]

That makes a lot of sense for the number of failures that keep being reported. I read somewhere that MXR's constant headroom technology is just a charge-pump circuit that doubles the voltage to 18V. The TLC2262 is 16V absolute maximum. So the voltage that is hitting these failures may be greater than the 16V max. Hmmmm.

-Frank

AD822 has +-18V supply voltage, +-30V input voltage, so hopefully I won't experience this problem anymore.
God bless Analog Devices

 

[spaghettiwestern]

Got my m87 back from Dunlop. Works fine, though the disappointing part is they said they couldn't recreate the failure. They replaced the entire electronics assembly in the enclosure just in case. $75.

In the end, wish I'd spent a little more time trying to track down the problem myself. Thanks for posting updates about replacing the op amp!

 

[boomertech]

Got my m87 back from Dunlop. Works fine, though the disappointing part is they said they couldn't recreate the failure. They replaced the entire electronics assembly in the enclosure just in case. $75.

In the end, wish I'd spent a little more time trying to track down the problem myself. Thanks for posting updates about replacing the op amp!

I have a feeling that they had a pretty good idea of what the issue is.

-Frank

 

[Precisionb87]

I've read that the issue is due to an IC not being properly selected within the circuit design:
MXR M87 Bass Compressor Repair - May Be Of Use To Someone?

I have a similar issue with mine (metering light fully lit all the time, no sound).
I plan on trying to fix mine (with having experience in SMT soldering).

Does anybody have the schematic for the M87?
If there are any other poorly selected components, I'd like to replace them while I'm at it. A schematic would be helpful.

 

[Kingkorg]

Found the issue with mine and it wasn't the opamp. The ratio switch was dead. The usual symptoms, no compression when engaged, leds go crazy... i fixed the existing one. It took some teethpulling in order to remove it from the board, but i made it. One of the internal sliders that make contact got broken off the rotating wheel.