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Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 5th Aug 2005, 11:58 pm   #1
Tim
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Exclamation CCH35 equivalent to 6K8G?

Hi all
Just finished another Emor globe.
As received this odd set was fitted with a CCH35 in place of the 6K8G.
Fair enough,some might say.
And in most cases this would be fine. It actually worked, very well.
The only trouble was that I received a nasty "tickle" from the metalising!
Why?
The designers had used pin 1 on the valve holder as a jump off point for the HT!
Not a problem with a glass valve of course, but nasty if a metalised valve is used. The
same thing would have happened with an ECH35/X61M etc.
I will certainly check next time, and always before using a metalised F/C in place of the 6K8G!!
Of course in sets designed for metallised valves, pin1 would be grounded.
Mind how you go!!

Last edited by Station X; 23rd Nov 2005 at 2:46 pm. Reason: Title made more meaningful.
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Old 8th Aug 2005, 1:41 am   #2
Darren-UK
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Default Re: CCH35 equivalent to 6K8G?

I've heard of this kinda thing before and if I remember correctly one of Chas Millers books makes reference to it and includes a warning of the inevitable hazards.

Without hunting round for the book and checking, as I recall it Chas implies this sort of thing with metalised valves is/was not uncommon

Last edited by Station X; 23rd Nov 2005 at 2:47 pm. Reason: Title
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Old 23rd Nov 2005, 12:40 pm   #3
jim_jobe
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Default Re: CCH35 equivalent to 6K8G?

I had the same experience with my R1155 years ago. I had changed the original valves for metallised "equivalents",not realising that the spare pin on the holders had been utilised as an HT point! I ended up having to remove the metallising with sandpaper!
Jim

Last edited by Station X; 23rd Nov 2005 at 2:47 pm. Reason: Title.
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Old 24th Dec 2005, 4:46 pm   #4
zak
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Default Re: CCH35 equivalent to 6K8G?

THE CCH35 is not an equivalent to a 6k8.In a parallel fed heater line it will be underun since it has a 7.5v heater.If you have an AC/DC set it may be ok since its a 200 ma heater.
Its always better to use the correct valve
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Old 24th Dec 2005, 8:05 pm   #5
quantum
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Default Re: CCH35 equivalent to 6K8G?

Some sets are surprisingly tolerant of having the wrong FC fitted - I once had a set which should have had a heptode 6A8 fitted when it had a triode-hexode 6K8 instead. Apart from some reduction in sensitivity it worked quite well, and I didn't realise that the wrong valve had been fitted until I got hold of the circuit diagram...
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