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 Post subject: Re-Valving Amps
PostPosted: Tue Mar 25, 2008 5:15 pm 
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Location: Rochdale
Hi all, was looking for a bit of advice on revalving an amp. It's a late seventies Marshall 50w Super Lead I bought in about 1997. I had a look at the valves inside and they're made by Mullard and written on them is 'Made In Great Britain'. From what I can gather (from t'internet) Mullard tubes haven't been made in the UK since the late seventies / early eighties making it a real possiblity that the valves have never been changed since the amp was manufactured.

Could valves operate ok after 30 years? I generally used it (over a period of three years) for an hour a night and a three / four hour session over the weekend so, around ten hours a week.

I've asked about a few other places and the responses have been -

1. "You idiot! Get them changed NOW! These things have a shelf life"
2. "You idiot! British made Mullard valves are collectors items. Leave them where they are"
3. "You idiot! Marshall? Burn it"

I'm more than happy to leave the valves in (the tone sounds ok but I've little to gauge it against) but could it damage the rest of the amp?

With thanks!

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 Post subject:
PostPosted: Tue Mar 25, 2008 5:48 pm 
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Joined: Sun Jan 20, 2008 1:56 pm
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Location: Lancashire. The correct side of the Pennines
Mullards were fitted to Marshalls when new, back in the '60's and early '70's

If they are the large EL34 power valves, then i'm afraid it's about time they were changed. I don't use Marshalls personally, only Fenders (fitted with 6L6 and 6V6 power valves), but I try and change the main power valves about once a year/18months

The small 12AX7/AT7 preamp valves are probably still ok - they don't suffer the same stresses as the power valves, although I change mine ever so often.

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PostPosted: Wed Mar 26, 2008 4:22 pm 
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Pre-amp tubes are usually the first to go microphonic, so if you crank that amp and it starts a howlin, thats usually the problem, I'd re-tube it anyways keep it runnin sweet and avoid break downs at gigs........if you gig that is.

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