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Old 31st July 2010, 05:41 AM   #1
loudel is offline loudel  Australia
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Default One channel louder than other

My Music Angel running 4KT88 in p/p has one side (channel) louder than the other. A little more info- the system has been running on and off for several months then one channel died. Took it to my Chinese 2nd hand audio repairer who replaced 4 (2x2) 3w resistors with 5w. Sound is back but noticebly less on the repaired channel. Have change the speakers/cables and outputs to no avail. I'm not very savvy about the inner workings but not afraid to change caps if need be (after draining them).Huffing it the repairer is a real chore as the unit weighs some 25k and I have to cart the thing in a suitcase on a plane.
Any suggestions?
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Old 31st July 2010, 06:10 AM   #2
TheGimp is offline TheGimp  United States
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1st I'd try switching tubes between channels, If you don't find any differences then start taking measurements.

I would recommend ohm-ing out all resistors and comparing the good to the low channel.

If no differences are found, then I'd measure the Output transformers and look for shorts. The problem is that the DC Resistance may be off considerably between channels. You will have to use a signal generator to verify winding ratios.
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Old 31st July 2010, 06:19 AM   #3
tinitus is offline tinitus  Europe
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maybe check your attenuator

bias ?

voltage ?
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Old 31st July 2010, 06:51 AM   #4
loudel is offline loudel  Australia
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Thanks, fellas, I had posted a similar query as I thought this 1st post did not get through. Will check and get back but it'll take me a bit of time.The guts of the Music Angel seem quite over-engineered compared to other (usually older) valve amps. Should the fault not be dtectable then I have a good mind to replace everything except the transformers and valves with simpler circuitry - there are several schematics floating around.
Regards
Lou
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Old 31st July 2010, 11:58 AM   #5
loudel is offline loudel  Australia
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Just an adjunct: have rolled the KT88s but same channel playing up. Then rolled the 12au/ats and seem to notice a small improvement in sound from affected channel.Could be onto something here - I have a couple of spare 12au/at and will roll them later this weekend.Fun.
Cheers and thanks.
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