Mullard EL34's? Originals?

Gassage

I've just revalved the Hiwatt.

Would these be the original valves from it? As dusty as hell.

And, any value in them?

ESchap

Mullard stated using that logo in 1971 approx.    There should be a 2 line code etched in the glass somewhere ..   First line will be xf and a number, next line will be a mix of letters and numbers starting with B  .... if you post that we can date them to the week for you ...

Value will depend if they have any life left in them i.e. they really need test results and also what number follows the xf

Gassage

XF3
B3K4 or 83K4

ESchap

4th week November 1973.  Made in Blackburn plant.   The xf3 was a fairly short lived version of the EL34.  The earlier xf2's get the premium prices.  

ICBM

While you can't tell for sure that they're good without measuring them properly on a valve tester, there are a couple of clues which show they're *not* in good condition -

If the silver getter flash at the top has stated to go thin, semi-transparent, or pinkish around the edges - that's a sign the valve has been leaking slightly, although it will continue working until it's all gone.

If the grey plates have "ribs showing" - horizontal lines in a discoloured patch in the middle - that's a sign the valve has been running far too hot, the lines are the shadows of the suppressor grid.

Valves with either of these signs may still work, but they're on the way out and worthless. If they don't, and look visibly in good condition, you then need a tester.


*Don't* try to clean the outsides of the valves, unless you're very careful - the print is very fragile and is easily rubbed off, which devalues them even though they work just the same. In particular don't wipe them with anything damp, or breathe on them and rub the glass - you'll take the printing off immediately.

Gassage

Well, new =C= in there- they always impress me in Hiwatts and a big upsurge in volume from the 103.

ICBM on one of them, there's silver going down the side of the tube?

ICBM

Gassage said:

Well, new =C= in there- they always impress me in Hiwatts and a big upsurge in volume from the 103.

ICBM on one of them, there's silver going down the side of the tube?

Is it a slightly different-looking  - more 'steely' - silver in a patch level with the plate, separate from the getter flash at the top?

If so that's another less common sign that the valve is knackered - it's evaporation/deposition from the grids having been run far too hot.

But in any case, if replacing them with modern valves gave a big increase in volume, they're ***ed. It would be the other way round if they were in decent condition.

I had a look at the pic of the amp you posted originally and at least a couple of them do look very thin around the edges of the getters too.

Gassage

@ICBM ;

This is quite a pretty feature of the valve that you don't get with new ones.

I do like aqua corrosion green.


https://scontent-lhr3-1.xx.fbcdn.net/v/t1.0-9/14222264_10153896581297066_1494064876923659944_n.jpg?oh=00fd0debf3323b7d960b39cb0925d379&oe=587DA960

Barrivee

Never fails to impress me just how much knowledge there is collectively on this forum. Seriously. 

Gassage

Barrivee said:

Never fails to impress me just how much knowledge there is collectively on this forum. Seriously. 

Nor me.

And the weirdest thing is- the more you engage with the forum knowledge giants like the lads who've posted here on thos very thread, the more you learn and the more you, in turn, can pass on to others.