HH MA150 Help Please

[Mike H]

Right I'll try that but can't do it till a week Tuesday. That's when we rehearse next and I can use a bit of volume. Can't try this in the house - neighbours might complain.
Mike

[Mike H]

Tried it last night. Output from Echo Send to a separate power amp didn't cause distortion. Took output from Aux In but got no sound, master vol control made no difference. I guess the problem lies around pre-amp output IC3 and IC4.

[Roly]

Output from Echo Send to a separate power amp didn't cause distortion.

Which means that all the individual mike preamp stages are okay, and the busses through to the Fx post amps are okay (Reverb Fx PCB), but the main post amp isn't.

I guess the problem lies around pre-amp output IC3 and IC4.

Yep.  And those 741's will be no loss to humanity or fidelity.   8|

[Mike H]

I'll try replacing the 741's and the electrolytics too just to be sure.
Wish me luck......

[Roly]

I'll try replacing the 741's and the electrolytics too just to be sure.
Wish me luck......

First replace the op-amps and re-test.

Then replace the caps if you're so inclined.

{There is madness in my method  :duh  :dbtu: }