Valves for testing (now with photos)

TonyR

Having a bit of a sort out in the loft and I came across a stash of valves that I assume are from one of my previous amps.

There are several EL34s, EL84s and 12AX7s that appear to come from different sources - Yugoslavia and Japan being identifiable. Makes include Mazda, Peavey and Phillips plus some with no markings at all. 

I know the EL34s won't fit any of my current amps, the others will, but without having to dismantle my amps to try the valves how can I go about getting these valves tested to see if they're any good?

ecc83

Even if you COULD be arsed to strip out your amp to check the valves I would advise against it. There is always the possibility that an unknown valve, output valve anyway, will cause damage to the amplifier, worse case a forked OPTraff!

Then, "testing" a valve can mean "Ooo! It lights up!" to a very in depth measurement of its parameters and curve tracing. The latter requires very sophisticated, read expensive test gear.

IMHO, get all the numbers of the valves and take some good photos and post them here. I dare say someone with the necessary kit will come in with you to test the valves and do a deal?

Alternatively, stick them on the bay as "Untested, offers"  ?

Dave.

TonyR

Thanks for your input Dave, I'll get the camera out then!

jpfamps

You can safely test the 12AX7s in an amp.

I'd test them in V1 as this will reveal if they are unusably microphonic.

The power valves, as ECC83 says, could cause damage, so unless you can sort this out yourself, I'd not attempt this.

TonyR

As suggested by @ecc83 here are some photographs of all of the valves I found:

Unnamed EL34s (Country: ?)

Back

Bottom (note missing Pin 6 - this is the same for all three valves)

Mazda EL34s (Japan) - these valves are slightly slimmer than the three above

Front

Back

Bottom (note all pins are present)

National Electronics EL34 (East Germany) - again slimmer than the three at the top

Front

Back

Bottom (note all pins present)

Unnamed EL84 (Japan)

Unnamed EL84 (Country: ?)

Peavey 12AX7 (Country: ?) - taken out of my 1990 Peavey Classic 20 amp (now long gone), probably had very little use

E1 12AX7s (Yugoslavia) - the white one is kaput ya?

 

Philips 12AX7 (Country: ?)

Unnamed 12AX7 (Country: ?)

Mazda 12AX7 (Japan)

Hopefully those photos will be useful - I do have the hi-res versions if necessary.

ESchap

OK,  I'll have a go ....

Top 3 EL 34's are Mullard, xf4's which is the last version of the EL34 they made.  There should be another line of code below it which will reveal the date of manufacture.

Both the the "Japan" Mazda's and the National are RFT (East Germany) made EL34's.  The open anode staples are the give away of RFT manufacture.

EL 84's not sure.

Peavey labelled 12Ax7's are Chinese manufacture

Ei's  yes the white one has lost its vacuum

The Phillips ECC83's,  I can see an I63 code on one.  That is a Mullard ECC83 code (the last version they made).  There will be another line of code which will reveal the manufacture date.

The unnamed 12AX7 looks like a Hungarian Tungsram.  The confirmation will be a silver "tab" on the leg of the getter ring.

The Mazda could be a Hungarian Tunsgram as well, again if there is a silver tab, it is.

Hope this helps.

guitargeek62

@jpfamps - I've got a box of ~200 old valves here that I can drop off to you if it's of any interest? Mostly mullards, but I think they're tv types for the most part? I've been meaning to catalogue them but just haven't made the time!

jpfamps

I would definitely be interested.

I've a couple of valve testers and assess a wide variety of valves.

guitargeek62

Cool, I'll try and drop them off to the shop this weekend. I don't know if many will be of any use to you but I'd rather know they *might* be of some use than just binning them outright!