Hartke Headache

[drewl]

UGH! I hate fixing other people's "fixes".
Someone was in here, who knows what they did.
This one's weird.
The preamp works up to a certain point, than distorts like crazy.
Somewhere the signal isn't getting to the master.
The power amp is putting out about 20w then clips but only if you use the chassis as a ground reference, it lost it's ground path.
I have a schematic that's pretty close, and I'm slowly working through it fixing stages as I go.....
edit: one other thing, always check the pots on these...4 of them were open!
I believe a couple open pots like the SS gain sent a screaming hot signal through the thing and did some major damage.

[drewl]

Well I found the bad opamp in the preamp, actually there were a few.
It works great, but only if you ground the neg speaker output to the chassis.
remove the ground and the relay drops out, so that part's working just gotta find out what's flaky with the protection circuit.

[Enzo]

Which... Hartke... is... it?

[drewl]

HA3500....I just had to rant about cleaning up someone else's mess.
Seems the person removed one of those ground tabs that connect to the board which was the chassis ground for the power amp output/speaker output.
It was dimming the lights at ~400+ watts output!