Fisher CA-800 Repair Question

i'm working on one of these too. got a new darlington in the blown channel and it worked for a while and then POP - dead. i haven't replaced those resitors yet... they measure the same from both channels - .7 or so.
 
Yeah, I have been following your thread too, hoping you would come to a solution, since it seems that we have the same problem (and I am just making semi-educated guesses and getting nowhere).
 
So, I ordered a service manual. I checked every resistor in the right side circuit. I tested them in-circuit, but if they read out of spec, I pulled them and tested them out of circuit. All of them test to spec, except R21. R21, according to the manual should be 10k, but on the board it's a 22k. That wouldn't be my problem, would it? It looks original.

Do you guys see anything else I could test? Just to refresh, originally Q05 was open, the darlington (IC01) was shorted, and one side of the R33 was open. I replaced Q05, R33, and IC01, and IC01 blows again in a few seconds, even though voltages are within range.

Thanks for your help thus far.

rightside.jpg
 
The two that were in it originally when I bought it were bad. I replaced them both, and the left side survived, the right did not. I did all of the above and smoked another on rhe right side. So I have a pile of 4 dead ones, but I only killed two of them myself :)

I have one more good one, and if I smoke it too, you might just see a curb alert on craigslist...
 
where is your curb? LOL - i have one good channel in my amp - together we have one good working amp.

(I also have the matching tuner and tape deck)
 
22K for that resistor is fine. They made a change to lower the current. Check Q05, Q07 and Q09.
It is possible you got counterfeit modules.
 
"counterfeit modules" - wow - i didn't think there were fake stk0080's going around.
i got mine from MAT and the channel worked for a few minutes on par with the other channel before it failed.
 
Sorry to dig up an old thread, but this one seems to have the most promise.

Where you ever able to successfully repair your CA-800? I was given one, & my symptoms match yours almost exactly. One channel has about 300mV DC offset, the other right around 62V. I have essentially zero experience repairing electronics and have a DMM to use for diagnosing. I can solder well enough & want to try fixing it myself. Rather than throw parts at it, I was hoping for some tips on what components to take measurements on. So far the 3 legged resistors & the STK packs are on my list. Anything else I should focus on if those turn out to be OK?

Thanks.

-Dave
 
I wish I had some constructive hints for you, but being that it's been almost 4 years ago, I don't remember anything other than I never did get it fixed, and I parted it out.
 
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