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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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23rd Mar 2018, 5:39 pm | #1 |
Heptode
Join Date: Apr 2016
Location: Cheltenham, Gloucestershire, UK.
Posts: 872
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Odd valve coating?
I've just finished off a little late 50's German radio and noted that all the valves have an odd pale brown/cream coating on their uppermost envelopes. The valve line up is very standard e.g. EABC80 etc. - and I've never seen this on other valves of their respective types ..... but I have in photos of similar [German] sets.
The coating is obviously not metallised screening and only covers the 'crown' of each valve. Most of my 'examples' are also crazing and flaking too. What is it and what was its intended purpose? A heat shield?
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23rd Mar 2018, 5:57 pm | #2 |
Hexode
Join Date: Mar 2012
Location: London, UK.
Posts: 347
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Re: Odd valve coating?
It could well be some kind of heat shielding. Could you post up a couple of pictures?
Thanks, Peter |
23rd Mar 2018, 6:55 pm | #3 |
Retired Dormant Member
Join Date: Jan 2007
Location: Westbury, Wiltshire, UK.
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Re: Odd valve coating?
Does a meter show it as conducting or not even though you say it's not metallic?
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23rd Mar 2018, 8:29 pm | #4 |
Heptode
Join Date: Apr 2016
Location: Cheltenham, Gloucestershire, UK.
Posts: 872
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Re: Odd valve coating?
Stand by for pics .... it's just a 'smear' covering the crown of each envelope top ....
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23rd Mar 2018, 9:00 pm | #5 |
Dekatron
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
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Re: Odd valve coating?
It could indicate it has been tested before putting in the production line.
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Frank |
24th Mar 2018, 11:13 am | #6 |
Nonode
Join Date: Jan 2010
Location: North Somerset, UK.
Posts: 2,129
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Re: Odd valve coating?
Could it be some sort of paint or varnish, not applied deliberately but a by product of prolonged use of the set in a workshop that applied such products by spray.
Particles would be suspended in the air, settle on the valves and be baked into a coating that might look intentionally applied. Possibly even valves re-used from a workshop set that became so encrusted that it was discarded after saving the valves. |
24th Mar 2018, 2:24 pm | #7 |
Heptode
Join Date: Apr 2016
Location: Cheltenham, Gloucestershire, UK.
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Re: Odd valve coating?
Patience Brethren ..... I'm just boxing the Little Devil up - and taking some shots!
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24th Mar 2018, 5:14 pm | #8 |
Heptode
Join Date: Apr 2016
Location: Cheltenham, Gloucestershire, UK.
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Re: Odd valve coating?
Your patience is rewarded ..... all valves feature this coating - and I've seen it on shots of similar sets located in Denmark etc. etc. What the devil is it and what is it's purpose?
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24th Mar 2018, 7:17 pm | #9 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
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Re: Odd valve coating?
Looks like someone dipped them in paint... perhaps to be able to tell if someone had fitted replacements from another shop?
David
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25th Mar 2018, 7:37 am | #10 |
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Re: Odd valve coating?
Maybe someone didn't like the look of the shiny black top to the valve so painted them.
Mike |
25th Mar 2018, 8:23 am | #11 |
Heptode
Join Date: Apr 2016
Location: Cheltenham, Gloucestershire, UK.
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Re: Odd valve coating?
I think Wrangler may be correct in that Grundig may well have 'dipped' their OEM valves prior to shipping these sets ............
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25th Mar 2018, 5:52 pm | #12 |
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Re: Odd valve coating?
Maybe to assist in checking how many valves accidentally dropped into people's pockets just before they went home?
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25th Mar 2018, 7:10 pm | #13 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
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Re: Odd valve coating?
Southern Germany/Austria... fondued valves? No sillier than cryogenic treatment.
David
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