EM34 and 6U5G - UK Vintage Radio Repair and Restoration Discussion Forum

Radio Tech · 10th Feb 2021, 7:55 pm

Hi Folks

EM34 and 6U5G difference,

I have looked up the two magic eye valves and I am a little confused over the two, the set I have should have the EM34 but it has been fitted with the 6U5G , the current valve fitted does not give any form of tuning display at all and now wonder if the EM34 and the 6U5G are compatible with each other, the base connections seem different and I think this is the reason why there is no green brilliance being displayed. Any thoughts on this please.

Regards

Ken

Sideband · 10th Feb 2021, 8:43 pm

Nope not compatible. That's not to say that the 6U5 can't be made to work after a fashion but it will need a base rewire. The EM34 has two anodes for a start since it has two sensitivities shown on its cloverleaf display.

I'm not surprised the 6U5 doesn't show any display since the target is pin 4 and on the EM34 it's pin 5. More worryingly pin 5 of the 6U5 is grid which means that HT is being applied so I wouldn't run it any longer with the 6U5 in place.

I'm quite sure if you search these forums, you will find information on EM34 subs or how to rewire for an alternative eye.

You could try swapping pin 4 and pin 5 over to see if the 6U5 will give any display.

jonnybear · 10th Feb 2021, 11:27 pm

I thought the Em34 had a universal octal base and the 6U5G has American UX6 base.I suppose if you rewire it with UX6 base it would be OK,6E5G has octal base but only has single triode apposed to EM34 having double.
John

paulsherwin · 10th Feb 2021, 11:58 pm

Confusingly, there are 2 versions of the 6U5G, one UX6 and the other IO.

You often find 6U5s subbed for EM34s, as the latter are scarce and expensive. A base rewire is needed though, it's not a pin compatible substitute.

Radio Tech · 11th Feb 2021, 9:22 am

Thanks Paul

Will look at base wiring and check

Ken

Chris55000 · 12th Feb 2021, 9:48 pm

Hi!

I have posted detailed information on this conversion before – I'll find the post and link it for you!

Chris Williams

10th Feb 2021, 7:55 pm	#1
Radio Tech Nonode Join Date: Dec 2012 Location: Bocking, near Braintree, Essex, UK. Posts: 2,071	EM34 and 6U5G Hi Folks EM34 and 6U5G difference, I have looked up the two magic eye valves and I am a little confused over the two, the set I have should have the EM34 but it has been fitted with the 6U5G , the current valve fitted does not give any form of tuning display at all and now wonder if the EM34 and the 6U5G are compatible with each other, the base connections seem different and I think this is the reason why there is no green brilliance being displayed. Any thoughts on this please. Regards Ken

10th Feb 2021, 8:43 pm	#2
Sideband Dekatron Join Date: Oct 2003 Location: Croydon, Surrey, UK. Posts: 7,580	Re: EM34 and 6U5G Nope not compatible. That's not to say that the 6U5 can't be made to work after a fashion but it will need a base rewire. The EM34 has two anodes for a start since it has two sensitivities shown on its cloverleaf display. I'm not surprised the 6U5 doesn't show any display since the target is pin 4 and on the EM34 it's pin 5. More worryingly pin 5 of the 6U5 is grid which means that HT is being applied so I wouldn't run it any longer with the 6U5 in place. I'm quite sure if you search these forums, you will find information on EM34 subs or how to rewire for an alternative eye. You could try swapping pin 4 and pin 5 over to see if the 6U5 will give any display. __________________ There are lots of brilliant keyboard players and then there is Rick Wakeman.....

10th Feb 2021, 11:27 pm	#3
jonnybear Octode Join Date: Nov 2010 Location: Cullompton, Devon, UK. Posts: 1,435	Re: EM34 and 6U5G I thought the Em34 had a universal octal base and the 6U5G has American UX6 base.I suppose if you rewire it with UX6 base it would be OK,6E5G has octal base but only has single triode apposed to EM34 having double. John

10th Feb 2021, 11:58 pm	#4
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,970	Re: EM34 and 6U5G Confusingly, there are 2 versions of the 6U5G, one UX6 and the other IO. You often find 6U5s subbed for EM34s, as the latter are scarce and expensive. A base rewire is needed though, it's not a pin compatible substitute.

11th Feb 2021, 9:22 am	#5
Radio Tech Nonode Join Date: Dec 2012 Location: Bocking, near Braintree, Essex, UK. Posts: 2,071	Re: EM34 and 6U5G Thanks Paul Will look at base wiring and check Ken

12th Feb 2021, 9:48 pm	#6
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,874	Re: EM34 and 6U5G Hi! I have posted detailed information on this conversion before – I'll find the post and link it for you! Chris Williams __________________ It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed!