"Cracling" MXR EQ

[drewl]

got a blue MXR EQ that's crackling big time....
sounds like a noisy plate resistor would in an amp.
any ideas on the cause?
I replaced the filter caps, and the input opamp....any other ideas before I replace the other 5 op amps?

[oc disorder]

fader clean perhaps ?

Gee havent seen one of those for a long time - seem to recall that the wrong gunk in the faders would cause havock I would clean with caig deoxit and as i recall they had some connectors that need cleaning as well.
It wouldn't hurt to replace all the IC's and perhaps if it still persists try a can of "freeze" on individual components whilst listening to the output ...
also check the bigger components haven't come adrift from the circuit board
sounds like you are on the right track though...
thats my 2 cents worth good luck !

[Enzo]

Op amps, if they are duals, have their outputs on pins 1 and 7. Scope those pins and see if the noise is there. Any controls that affect the noise are AFTER its source. SHouldn't take more than 10 minutes to change out 5 8-leg ICs anyway. On low voltage circuits like this, semiconductors are far and away the most common source of noise.

[drewl]

yeah, IC pinouts were burned into my head long before tube pinouts!
the noise is so very low it barely shows up on a scope, but a couple milli-vanilli volts of static is all it takes once it hits the front end of an amp!

Just looking for ideas before changing all those "vintage" 4558 amps......maye I can sell them on fleabay!
thanks guys.