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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 3rd Feb 2024, 2:11 am   #1
Chris55000
Nonode
 
Join Date: Aug 2007
Location: Walsall Wood, Aldridge, Walsall, UK.
Posts: 2,920
Default Very Unusual radio fault in French set

. . .I thought I'd share this case history from a French book of "500 Pannes" - roughly "500 Faults!" - it was both an unusual symptom and it had an even more unusual cause!

. . .In French the description given was :-

"302. - Récepteur alternatif. Manque de sensibilité."

"Le récepteur comporte les lampes suivantes : ECH42, EF41,
EBC41, EL41, GZ40 et EM4.
L'audition est normale et puissante sur les émetteurs locaux'.,
mais avec, de part et d'autre de l'accord, une coupure
nette, comme s'il y avait un réglage silencieux. Aucune réception
èles stations éloignées.

Cause : 1e défaut provenait d'un court-circuit · presque franc
entre la grille et la plaque de J'oeil magique EM4, monté suivant
le Fig. 184"

. . .In English :-

. . ."Fault 302 :- Unknown Set - Lack of Sensitivity"

"Five-Valve Superhet with magic-eye tuning indicator. Valves ECH42, EF41. EBC41, EL41, GZ40 and EM4.

Good loud reception from local transmitters, but on de-tuning the reception cuts out either side of the local station and no distant transmitters can be received".

"The cause was traced to an almost complete short-circuit between the indicator control-grid and one of the anodes within the valve, see circuit Fig.184". (redrawn below)

. . .(The description doesn't say how the display was affected!)

. . .Magic-eye indicator valves operate at very low anode and target currents and a fault causing overheating of the electrode structure within one is virtually unknown, I've never come across an indicator with an electrode system fault in it, has any other Member?

Link to the book :-

https://archives.doctsf.com/document...39&num_serie=7

Chris Williams
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It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed!

Last edited by Chris55000; 3rd Feb 2024 at 2:40 am.
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