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man just saw this! i guess orange board posts dont generate emails to user?!?!?
hope you got it fixed but if you still have it, it's normal for you to induce hum into audio by touching some of the legs on an STK amp chip. no worries there. with a new chip in place crackling is likely to be from another source like the preamp/tone control electronics or dirty switches/controls. first place i would start is cleaning all controls and switches with an electronics cleaner like Deoxit. for more help on this i suggest you join the forum tapeheads.net
even though its a tape forum, there are many helpful and knowledgeable people there with no ego problems. it's one of the freindliest and most helpful vintage audio groups on the web.
After reading your instructables with lots of interest about bringing back to life an old receiver I signed up because I was hoping that maybe you could help me out with some problems I'm having with a casseiver I try to rescue. So far I've restored lots of gear with succes, going from amps, lots of cassette decks, turntables, etc. So here I go, picked up this casseiver that was going to be thrown away, a cheap Schneider team 20 but I liked the looks of it. It had one dead channel. I cleaned him completely, put new belts in it, bought a new stk chip for it, did replace some caps that had leaked. Since the stk was hard to access, I soldered it back in but used small wires soldered to the pins to bridge it to the printboard. The casseiver actually worked for a while(few weeks) so started buying new alu knobs and stuff like that to make it look nice.
One day I pop it on and have a lot of noise and crackling and notice that when touching the wires on the stk it gives lot of intermitent noise. Now, I'm not an ace in soldering. So I decided to try to resolder the stk in how it should, directly on the printboard(pain in the ass). Stk is bolted firmly with thermal paste to the heathsink, soldering looks ok but the noise got worse. It's very frustrating.
I don't know if the stk fried or if my soldering is crap. The thing is that I found a schematic of that stk part and noticed it's only rated 2x7wpc. It's a stereo stk amplifier. So i'm considering replacing the stk with an external amp board with some more power and hopefully less noise.
I have no blown fuses and except for the crackling noise, everything works. I understand every step you explain. The part you mention about finding the line level is not completely clear to me. I have lines on the board and no cable. Pin 1 and 15 are Uin L and Uin R. I also know where the ground is. I suppose this is the line level input from the preamp. I have a small class T amp to test before I buy a new amp board. My question is, do I just have to remove the stk and just run one red, one white and one black from the Uin R and L and ground from the board to the external amp (and the speaker wires of course) in order to get audio?
I have noone that can help me out with this and I'm in no way a technician. Everything I did so far I've learned from reading on the net. I learn quickly. Your expertise would be greatly appreciated. Thank you very much for your time and reading my stuff.
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