Pye 39j/h

[Bushbaby]

Hi All
I 'be moved a number of radios into my new man cave (Christened Crinkly Bottom by a couple of friends.) In moving my Pye 39j/h into its new home I took the back off to have a good look at the chassis. I couldn't help noticing that it's been fitted with a 6V6 in place of one of the EL33's???????

Rob

[Murphyv310]

Probably will sound ok, may increase the harmonic distortion a bit though, may surprise you the things you find in old sets. My 39 J/H is a superb set, now safely on display in Bob,s museum.

[Bushbaby]

I think that I have 2 x EL33's as spares. I'm sure that I bought these before they command the silly prices I have seen them for sale. I shall try this will the 6V6 first (checking that the set has been modified to use it first).

Thanks

Rob

[Murphyv310]

Both valves are pin compatible but the 6V6 has a lower gm so if fitted alongside the EL33 there will be a mismatch increasing distortion. Most likely there has been no mods to do this as it fitting two different valves of different characteristics is not the correct way to do things. Two EL33's is the right way to go. These sets are excellent once restored.

[Bushbaby]

do the EL33's have to be matched pairs?

[Terry]

I doubt very much that Pye fitted matched pairs in the first place so I wouldn't worry.

Early transistors were often supplied in matched pairs because of the wide difference between individual samples but I'm not sure that you will find matched pairs of the more modern types. Valve performance is much more consistent than those early germanium transistors!

If the pair you have are new, that should be sufficient.

Otherwise two valves in similar condition should do the trick - if you've been happy in the past with the 6V6/EL33 mismatch, they can only be an improvement!

[Murphyv310]

Hi.
Totally agree with Terry. Two EL33'S is the way to go, its unlikely that Pye would have have them matched but they would have been off the same batch. Two 6V6 or 6L6 would work as well but of course the anode impedance and GM is different so output would be lower with these valves. The EL33 is a good valve and will be long lived, remember to replace any coupling and decoupling capacitors as a matter of course, the coupling caps can as you know pass DC when they get leaky which they will be which then makes the control grid more positive in relation to the cathode which in turn increases anode current, this shortens the valve's life and in an audio output stage increases the stress on the output transformer.

[Bushbaby]

Thanks Terry/Trevor,
I don't believe that I have switched this set on so I cant tell you what it sounds like. Now that I've move a number of 'woodies' into my workshop (Crinkly Bottom) its my intention to work my way through them restoration wise (recap, replace, rewire where necessary etc.) I have 2 PE60's to work on too but in both cases the dial glasses have been damaged.

Regards

Rob

[Geordie McBoyne]

A few near equivalents of the EL33 exist such as the Brimar 6AG6G and the Mazda 6P25, also worth considering is the Marconi-Osram KT61. All are high slope power pentodes with a slope of 9 to 10mA/V, rA in the region of 40 to 50 Kohm.
http://www.r-type.org/exhib/aad0232.htm

Geordie McBoyne.