Hartke HA3500 - pops and crackles with EQ on

[davehux]

Press in the EQ button, the graphic lights up, but I get snap, crackle and pop out of the speakers. Really loud pops even on less than 1 on the master.

Switch off the EQ and it's quiet as a mouse all the way to 10 and sounds lovely.

I've read that Hartkes are prone to dry joints, and I've currently got the thing in bits, but I can't spot anything on the main board or the EQ board that looks remotely unusual.

Can anyone point me in the right direction? I'm competent with a soldering iron and don't really want to spend a lot of money on it, as it's not an expensive bit of kit these days. However, when it's on form, it's a hell of an amp, so I'm loathed to scrap it

Cheers

[mikeydee]

Might be dodgy pot wiper but if none of the pots effect it then suspect one of the op amps is shot. Does the noise get effected by guitar signal? If so probably op amp problems.

Mike

[Phil Starr]

Most of the Hartke dry joint problems were in the power supply, unsupported capacitors held in place by just the solder.

Anything to do with the eq and cleaning the sliders is the first point of call. possibly even the switch

If you are still struggling to locate the fault then get some freezer spray. It rapidly cools small components one at a time and if that sudden cooling makes the fault dramatically worse or better then you have located the little devil.

Good luck

[davehux]

Thanks Phil - that gives me a starter for 10

[icastle]

Hartke had numerous problems with dry joints some time ago.

I've found that the easiest way to track them down is to very carefully tap around the inside of the amp with something non conductive until the problem starts or stops and investigate from that point.

Once you've found the specific area then just desolder and resolder everything around it - these boards are sent through a solder bath after assembly, so chances are that there'll be more than one crap joint there.