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Tube amp repair.

Hi, my name is Brian and I'm new to to the site and forums in general so let me know if there is somewhere else I should be asking this question.... My 1st tube amp was a Chinese Yaquin MC-100SE (ya I know, that's my problem right there, lol) that sounded pretty decent at first then started occasionally red plating the kt88 tubes. At the time I also did not know about using a Variac so this could could have started the problem or it it could just be a 50 lb paperweight. Anyway I'm wondering if anyone knows of someone in Minnesota (preferably SE Mn) who does tube amp repair. The thing has been taking up space for a few years and I'm trying to figure out what to do with it. Not sure it's worth the cost of sending it anywhere but thought if there was someone within drivin distance that would take a look I might do that.

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czarivey
5,671 posts
 

New Chinese amp will be cheaper. That's how it usually works with Chinese gear pretty much anywhere.

brian61's avatar
brian61 OP
2 posts
 

Could well be.

russ69's avatar
russ69
3,360 posts
 

Two questions. Why do you need a variac and why don't you think it just needs new tubes? 

mceljo
1,348 posts
 

I had a Yaqin MC-30L amplifier that world flawlessly for me for several years and a friend of mine has it now.  I think Yaqin is above the Chinese "junk" stereotype, but repairs can still be expensive.  My local shop (across the country) charges around $200 per hour for repairs I believe.

I'd check with some of the local hi fi shops as they may have a person that does their repairs.

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oldhvymec
5,101 posts
 

Is there a bias adjustments on each side. The desired voltage is written on the side 2V. There should be pots for the 6SN7 too. They are under the plate. Check the bias first, then it's most likely a bad valve. They have a soft start circuit, no need for a variac. Few newer valve amps require a variac. Most of the older ones if they have been worked on at all, something has been added to aid in a softer start.

Regards

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