| K200B6 [message #28291] |
Tue, 10 August 2021 17:08  |
aeroboy47
Messages: 15
Registered: September 2019
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Junior Member |
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I posted last year about this amp. It's the one that had a #12 wire soldered across the fuse and had several bad transistors and the shorted bias diodes. After I got the parts replaced and the amp working again, I was concerned about the 120mv DC voltage at the output. I'm back working on it now and I have replaced other parts and the DC voltage at the output is now 48mv DC. I'm guesssing that 0vdc would be ideal but dont see that happening unless someone has ideas about what to do nest. I have replaced Q1-Q4, Q701-Q709 and CR701-CR703. All the voltage readings I have been able to take are very close to the schematic values except Q707 collector is at -2.4 vdc and Q703 collector is at +4.6vdc. Any technical expertise would be appreciated.
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| Re: K200B6 [message #28292 is a reply to message #28291] |
Wed, 11 August 2021 09:53  |
stevem
Messages: 4773
Registered: June 2004
Location: NY
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Senior Member |
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That's strange that the collector of 703 is positive when it should be negative!
What does the base of 705 test at and the collector of 701 test at?
[Updated on: Wed, 11 August 2021 09:54] Report message to a moderator |
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| Re: K200B6 [message #28321 is a reply to message #28291] |
Fri, 03 September 2021 17:53 |
aeroboy47
Messages: 15
Registered: September 2019
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Junior Member |
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The amp is back together. I just went ahead and replaced the FD111's with 1N4148's. It works but still has problems. the voltages at the collectors of Q707 and 706 went up slightly. The cathode of CR704 is -.72vdc (anode is -3.2vdc)and the anode of CR703 is 1.24vdc (cathode is 4.8vdc).The back of the amp seems to be getting hotter than it should but the fuse is not blowing and I have had it on for over an hour.
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