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In Reply to: I spoiled my Unison Research amplifier posted by tubers on February 16, 2007 at 13:50:14:
I have the same brand Performance amplifier, I had the same facility a few times dependable replacing new KT88 tubes drifting bias outside of range (some tubes are problematic)all you have to do is removing bottom plate and replacing the fuse, it is not difficult and no need any technician.
Follow Ups:
Follow-up after the technician's visit:When I removed the cover I saw that the resistor got loose from the circuit board. He soldered the disconnected resistor in place, but one of the Sovtek KT-88 tubes behaved abnormally (it did not produce blue light like others and was colder than others and caused scratchy sounds from the right speaker). We switched the amp off, reversed the tubes, and the bad tube behaved in the same manner in another socket. OK, he said, one tube is bad. For lack of other tubes, I inserted into the right channel two very expensive GEC KT-88 tubes, one of which became red hot and we immediately switched the power off.
The question is - should I insert four GEC tubes or it is very risky and this is the amplifier problem?
You may put every KT88 on your amp, and after turn on,just watch the tubes if they are healthy and /or their bias are inside of your amp's bias range everything would be fine,otherwise your one channel fuse will be blown,and it is inside your amp (small glass fuse
and might be 0,8 mA value)and replace it with a new one and try to find safe new KT88s for your amp.
I opened the cover and saw that one resistor (I believe it's a resistor) marked 5W100EJ got loose from the circuit board. I don't know whether it was initially soldered or mechanically connected to the circuit board by the manufacturer. There are several such resistors in the circuit. I called a technician who will come later today and, in the meantime, I will go to the matket and look for fuses (one type marked 250VT 500L and the other type 1AL 250VP).I will keep in touch. Thanks for assistance!
I will do that and report.
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