just an update -
I ended up replacing every IC on the preamp - after a fiddly 'biamp crossover' pot that almost sent me back to square one - it was one of those 'everything works!' and then put in back in the chassis and nothing works again! - but luckily just a bad solder contact -
we are back in business!! I replaced the flimsy ribbon cable with individual stranded wires - time consuming but much more sturdy - and had to replace a couple broken send/return jacks on the back -
looks like there was something serious that happened to the +/- 15 rails because all of the op-amps were fried. but I've ran it for quite a while now and we seem to be back in business. I did replace the zeners and regulator transistors for the low voltage rails - think those were the initial problem.
anyway, thanks guys! kind of a long saga but all's well that ends well
I ended up replacing every IC on the preamp - after a fiddly 'biamp crossover' pot that almost sent me back to square one - it was one of those 'everything works!' and then put in back in the chassis and nothing works again! - but luckily just a bad solder contact -
we are back in business!! I replaced the flimsy ribbon cable with individual stranded wires - time consuming but much more sturdy - and had to replace a couple broken send/return jacks on the back -
looks like there was something serious that happened to the +/- 15 rails because all of the op-amps were fried. but I've ran it for quite a while now and we seem to be back in business. I did replace the zeners and regulator transistors for the low voltage rails - think those were the initial problem.
anyway, thanks guys! kind of a long saga but all's well that ends well