#1
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Columbia 360 "Series B" Amp Repair
I have this formally wonderful Columbia 360 record player that was handed down through my family. After some lubrication and cleaning to the changer it worked and sounded great for 2 years or so. Slowly it developed a low hum...you guessed it now there is no sound.
Before I start rebuilding the amp is there anything I should check to verify there is no major damage that won't be easily repaired? I attached a photo of the schematic since I see no specific model numbers. Amp is listed as Series B amp and cabinet 2201. Thanks in advance for your time and assistance. Bill http://imgur.com/OL9Ij |
#2
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Sounds like the electrolytic filter caps took a dump. Sounds like it's in need of a re-cap.
__________________
"It's a mad mad mad mad world" !! http://www.youtube.com/user/mwstaton64?feature=mhee |
#3
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That's what I thought as well but would bad caps alone cause no sound not even hum?
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#4
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Do the tubes light? Is there B+? Is the speaker properly connected?
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#5
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Maybe a tube bit the dust. You need to check tubes and voltages first.
__________________
"It's a mad mad mad mad world" !! http://www.youtube.com/user/mwstaton64?feature=mhee |
Audiokarma |
#6
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As long as the output transformer (rightmost on the schematic) has good windings,
this amplifier is easy to rebuild. All other parts are esaily available. This is a rather basic amp, with series-string tubes, but being a push-pull unit (two output tubes), it may be worth keeping and rebuilding, as noted above. Good luck! |
#7
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Thanks for all the advice!
The windings seem okay as best as I can tell, VOM reads 196 ohms and the tubes do light. I'll let you know how it turns out. Bill |
#8
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Often, the filter caps cause hum and then the cap becomes very leaky or shorts. When this happens, the shorted/leaky caps will destroy the rectifier tube and/or the surge resistor in the power supply. When this happens, the amp will be dead because there is no B+ voltage being developed. Since the output transformer test good, I'd replace the electrolytic and paper caps and then I'd check voltages.
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http://www.youtube.com/user/radiotvphononut |
#9
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Thanks for all the advise. So far I've replaced the electrolytic and paper caps (no change) then changed 35Z5GT. Now I have low hum but no audio from the cartridge. Cartridge is working when connected to a known good amp (used aux in on receiver). Next I'll change the 12AX7, will let you know what happens when the new tube arrives.
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