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Old 13th April 2005, 03:44 AM   #1
Brian Donaldson is offline Brian Donaldson  United States
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Default Kenwood KR-750

Ok, I bought a unique Kenwood reciever on Ebay that didn't work for $5. I have a working model I bought new, and still have. It's a really nice sounding reciever for early 80's Japanese.

Anyway, I opened it up and it had tin foil over the fuse and one of the outputs had a big black hole in it, so I set it aside. Then I found a new set of outputs on Ebay, So I started poking around. I cut the dead pair of outputs out so the protection circiut would let it power up and see if the other channel worked. The funny thing is they both now work, although the channel without output transistors badly distorts if you put any volume to it.

Just from following traces, it seems to be a CF output Shitklai pair and the pre driver first transistor of the pair is feeding the output, although greatly current limited. My question is ... Does this mean that the only problem is likely the blown outputs?. I'm afraid of just throwing a new set of these not so easy to find original manufactured (not crappy counterfit NTE garbage) outputs in just to have some bad Vbe diode stack blow them or something. I'll check and adjust the bais of course, and bring it up with my variac, but a little reasurance would help.

Another weird thing, this has 50V rails at the outputs, but it's only rated at 60W @ 8 ohms RMS. That's a lot of waisted voltage for an amp that only needs to put 32V peaks. Maybe it helps keep everything in the linear region and helps it sound good.

If any of you wise old tecks can advise, I would be greatfull
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