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Diagnosing problem to repair vintage amp

T

Tinsleysboy

New Member
I hope I'm posting this in the right forum. I recently acquired a nice stack of Nikko separates (Alpha II, Beta II, Gamma I) and the amp has an issue. I am hoping to narrow down the likely culprit before just replacing all the capacitors. I tested the amp by connecting it pc > preamp > amp > speakers, but never even got to play any music. With no source the left channel was idle, but the right channel was getting loud popping noises every few seconds and the VU meter for the right channel was jumping all the way to the red. The left meter was dead still. Any help is greatly appreciated before I decide to just recap the entire thing.
 
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I wouldn't rush into recapping it before you work out what's wrong, start with the basic things, look for relays open and closing, electrolytics that are bulging and or leaking, get a magnifier and go over the PCB and look closely for cold solder joints etc. Other more knowledgeable souls may chime in.

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Thanks for the input. I didn't mean to imply that I'm in a rush, and I intend to start looking for the small things. I was just hoping someone may have had the same problem before and knew which transistors or caps to examine more closely. I took a glance when I was home over lunch and didn't notice any obvious bulging or leaking, but I will have to take it apart further for a better view when I have time and no dog or fiance fighting for the space.
 
okay but you need to perform an inspection.. as hypnotoad recommended. Post pics if in doubt of anything.
 
It sounds like the classic noisy pre driver transistor in your right channel main amp. A meter will show this compared to the other channel. Freeze spray will also be able to help point out the culprit.

Of course, check for cold solder joints through out the entire amp.
 
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century tek said:
It sounds like the classic noisy pre driver transistor in your right channel main amp. A meter will show this compared to the other channel. Freeze spray will also be able to help point out the culprit.

Of course, check for cold solder joints through out the entire amp.
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I'll be sure to check there after scoping out the board for bad soldering. That's the kind of suggestion I was hoping for! Hopefully this weekend I can get some free time to tear into it and get a good look.
 
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