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 Diagnosing blown valves 
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God Of The Sun
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Joined: Mon Jul 10, 2006 10:49 am
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Location: london baby
Post Diagnosing blown valves
How exactly do I do this?

I'm hoping the valves have gone and its not something more serious

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Fri Jul 01, 2011 2:24 pm
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Superhero
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Joined: Sun Nov 24, 2002 8:51 pm
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Post Re: Diagnosing blown valves
If HT fuse has blown, its poweramp valves died.
They last aprox 2 years for me gigging.
Anymore details? If no life its them

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Fri Jul 01, 2011 4:39 pm
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God Of The Sun
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Joined: Mon Jul 10, 2006 10:49 am
Posts: 4801
Location: london baby
Post Re: Diagnosing blown valves
Amp turns on as normal

I turned it on for a lesson - flicked it off standby.... no sound.... I didnt have time to diagnose it as I had a student.

It all powers up, and the valves a light up (dimly)

I got it second hand a 18 months ago (bogner XTC) its the american one and i use a step down transformer.

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Suhr GG > peterson strobe 2 > EB wah > Rothwell compressor > Suhr Shiba > Suhr Riot > Jam boomster > Jam ripple > Delay Llama Bogner XTC > EB volume > bi-chorus > cornford 2x12


Fri Jul 01, 2011 7:04 pm
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Superhero
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Joined: Sun Nov 24, 2002 8:51 pm
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Location: away from here
Post Re: Diagnosing blown valves
valves glowing is not a sign they work.
check HT fuse.
you may need a shop/tech

http://www.chandlerguitars.co.uk/ are very good.
avoid Denmark street!
http://www.marshallamps.com/resources/s ... cement.asp

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old fan since 1986.
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Fri Jul 01, 2011 7:15 pm
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Viking Kong
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Joined: Fri Feb 18, 2005 6:46 pm
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Location: Torrance California
Post Re: Diagnosing blown valves
When I have had preamp tubes go bad my amp sounded pretty bad. It had little volume, and very little distortion. Since its a mesa boogie single rectifier it usually has more distortion/gain than I need.

Some times you can gently tap a tube with a pencil eraser, and see if one is much noisier than the rest. Other things to look for are if one is glowing noticeably brighter, or less bright than the rest. The problem I had on my bad preamp tube was it lost vacuum, and the silver stuff at the top of the tube turned black.

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Sat Jul 02, 2011 12:07 am
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