50C5 valve with a strange fault. - UK Vintage Radio Repair and Restoration Discussion Forum

Glowing Bits! · 14th Sep 2018, 2:26 pm

This would be a simple question but is likely to end up long and winded, what a surprise!
I'm nearing completion on an American GE set but have come across an issue with the above output valve when running it on the valve tester.
The first fault I found was that pins 2 & 5 (both internally connected to G1) seem to be operating the heater, as is pin 4 which is the correct pin for the heater, is this normal?
The other thing I couldn't help noticing was the fact that there appears to be some form of electrical leakage between the anode and cathode, this would usually be a bad sign at the best of times.
Would this render the valve scrap?
I don't fancy the idea of having 50v ac as opposed to the usual negative voltage driving the grid!

Any help/advice greatfully appreciated.

Regards, Rick.

ms660 · 14th Sep 2018, 2:45 pm

Are the heater connections correct, 5&3 mixed up?

Lawrence.

Boater Sam · 14th Sep 2018, 2:52 pm

Are the marking clear that it is a 50C5?

The structure inside of a 50C5 is very easy to see, can you establish that the pins are connected to where they should be?

If it is a faulty valve something quite horrible has happened to it.

Nuvistor · 14th Sep 2018, 2:52 pm

Are the leaks in the valve or valve holder?

Glowing Bits! · 14th Sep 2018, 3:40 pm

Thanks for the replies so far, the usual pins of 3 & 4 are working correctly for heating the valve, the filament return on the machine is to pin 3, pins 2 & 5 should not be connected to anything other than G1, but the valve still glows on these pins.
Another valve has been used on the machine to verify that the holder is working as it should.
When lightly (with finger only) tapping the valve whilst holding it (no test gear needed), there is a slight movement sound, I'm now wondering if the valve has had a bang at one time but not enough to break it.

All of this is more of a curiousity if anything, these are available on a well known auction site if need be.

Rick.

ms660 · 14th Sep 2018, 3:44 pm

Sounds terminal.

Lawrence.

14th Sep 2018, 2:26 pm	#1
Glowing Bits! Octode Join Date: Oct 2011 Location: Wrexham, North Wales, UK. Posts: 1,457	50C5 valve with a strange fault. This would be a simple question but is likely to end up long and winded, what a surprise! I'm nearing completion on an American GE set but have come across an issue with the above output valve when running it on the valve tester. The first fault I found was that pins 2 & 5 (both internally connected to G1) seem to be operating the heater, as is pin 4 which is the correct pin for the heater, is this normal? The other thing I couldn't help noticing was the fact that there appears to be some form of electrical leakage between the anode and cathode, this would usually be a bad sign at the best of times. Would this render the valve scrap? I don't fancy the idea of having 50v ac as opposed to the usual negative voltage driving the grid! Any help/advice greatfully appreciated. Regards, Rick.

14th Sep 2018, 2:45 pm	#2
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: 50C5 valve with a strange fault. Are the heater connections correct, 5&3 mixed up? Lawrence.

14th Sep 2018, 2:52 pm	#3
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: 50C5 valve with a strange fault. Are the marking clear that it is a 50C5? The structure inside of a 50C5 is very easy to see, can you establish that the pins are connected to where they should be? If it is a faulty valve something quite horrible has happened to it.

14th Sep 2018, 2:52 pm	#4
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,433	Re: 50C5 valve with a strange fault. Are the leaks in the valve or valve holder? __________________ Frank

14th Sep 2018, 3:40 pm	#5
Glowing Bits! Octode Join Date: Oct 2011 Location: Wrexham, North Wales, UK. Posts: 1,457	Re: 50C5 valve with a strange fault. Thanks for the replies so far, the usual pins of 3 & 4 are working correctly for heating the valve, the filament return on the machine is to pin 3, pins 2 & 5 should not be connected to anything other than G1, but the valve still glows on these pins. Another valve has been used on the machine to verify that the holder is working as it should. When lightly (with finger only) tapping the valve whilst holding it (no test gear needed), there is a slight movement sound, I'm now wondering if the valve has had a bang at one time but not enough to break it. All of this is more of a curiousity if anything, these are available on a well known auction site if need be. Rick.

14th Sep 2018, 3:44 pm	#6
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: 50C5 valve with a strange fault. Sounds terminal. Lawrence.