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Deadman

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My Marshall AVT50 used to be a great amp. I looked through the vent in the top a couple of years ago to see it glowing away. Recently, it hasn't sounded so good. Lo and behold, today I check the valve and it's lifeless.

I've ordered a JJ Tesla, ?8 odd off Ebay. I'm expecting great things! :D

What do you guys recommend/use? Obviously this is only a preamp valve (ECC83/12AX7) and I understand that it can get expensive. My old Fender Twin cost me ?75 to revavlve (Groove Tubes).

Lastly, any tips for me? It seems a really simple task to carry out?
 
Be aware about new JJ tubes. I have two on my 18 watt clone and one is very microphonic. Buy them from a reputable seller and return them if they became microphonic with some hours of use.
 
OK Luis.
The ebay store has 100% feedback and they're a top reviewer too. They do a great review of the JJ. I'll be sure to follow your tip though! :wink:
 
Just a quick question:

Is it safe to handle the valve with your bare hands prior to installation? Or do you have to use a cloth/gloves? (like a high-wattage car headlamp bulb)
 
I?ve never wear gloves. I use my hands to put them and not problem.
These JJ sounds good enough, specially on a Marshall style amp.
Another beware, one of the JJ 6l6gc I have on my 5e5-A clone went microphonic too after a short period of use again.
 
Got a pair of JJ 6V6's on my tweed deluxe clone, also use their 12ax7 and have a 12au7, never had a problema and they have great tone...

you can handle them with bare hands...

the only time you shouldn't handle them with bare hands is if you have to handle them while hot, because you might hurt yourself (but even that shouldn't be a problem, because tubes should be allowed to cool off before being handled anyways, because you might ruin them if you don't)...
 
OK Bruno, thanks.
The new valve will be here tomorrow. I wonder how much difference there'll be to the tone?
 
The reason that you don't handle valves...tubes or glass lamp elements with bare hands is because the oils from your skin leave a film on the glass surface which heats up that particular spot.
 
That was what I thought, Oz. I don't reckon I'll handle it, just in case.
The **** thing was delivered this morning but the postman couldn't fit it through my letterbox. Now I have to wait 6 hours before I can pick it up from the Post Office. ****! Can't wait to get it installed...the amp sounded, well, even fuzzier last night. :-?
 
Ozeshin said:
The reason that you don't handle valves...tubes or glass lamp elements with bare hands is because the oils from your skin leave a film on the glass surface which heats up that particular spot.

I've never had a problem with that sort of thing. It might apply to modern car headlamp bulbs, but valves are plenty sturdy enough.
 
Tube manufacturing these days is a hit and miss game and there is no guarentee that NOS tubes are any better than new ones.

Best thing you can do with tubes is find someone who knows their stuff and see if they have a tube tester. They should be able to match sets up for you.

I have a stack of old NOS tubes in a box. Mullard, Phillips, GEC, Brimar to name a few. Some have been matched up.

Of the newer ones I've found Svetlanas are ok and pretty good value for money. GT's are graded and are usually good but you pay extra for all that fancy stuff.

If you must handle tubes then wipe them gently with a clean cloth before you put them away in a box or just after you put them in your amp. OBVIOULSY, DONT' DO THIS WHEN THEY ARE HOT BECAUSE YOU WILL SURELY REGRET IT.
 
AND FOR THE THICKO'S OUT THERE.

DON'T EVER HANDLE THEM WHEN THE AMP IS SWITCHED ON AND DON'T EVER USE A DAMP CLOTH TO WIPE THEM.

BETTER STILL...... LEAVE THEM ALONE!
 
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