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 Marshall AVT50 Guitar amp repair		  New Topic  Reply to Topic
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davidkien68
New Member

Japan
1 Posts
Posted - Jan 09 2015 :  2:24:28 PM  Show Profile  Reply with Quote
HI,

I have a Marshall AVT50 which has stopped working. The speaker has been blown but there are also other problems. I can get output from it by plugging a CD player into the CD in jack and unsing headphones in the headphone socket. Both of the clean and drive channel LED's light up but I only get a slight hum from the drive channel through the headphones. The main fuse is OK.

Clearly I need a new speaker, but there is obviously another issue. The guys at Marshall that I've spoken to (parts dept) suggested that the power stage of the amp could be blown. Does anyone have exoprience of this amp/problem?

Richard.

(Edit...Remove spam link...is this a sophisticate spam bot? Curiosity compels me to not close the post and find out if the link reappears.)
Edited by - davidkien68 on Jan 12 2015 02:58:08 AM

Aaron Cake
Administrator

Canada
6718 Posts
Posted - Jan 10 2015 :  10:26:59 AM  Show Profile  Visit Aaron Cake's Homepage  Send Aaron Cake an ICQ Message  Send Aaron Cake a Yahoo! Message  Reply with Quote
It does suggest the output stage of the amp is damaged.

Not being familiar with this exact amp, I can only suggest the generic procedure. You need to trace the signal through the amp with a scope, taking not of where it disappears and whether or not it increases in amplitude when expected.

That said, probably the first test is to check the output stage which is probably made up of MOSFETs. If you find signal at their gates, but nothing at the output, it's a fairly good guess the MOSFETs are fried.
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