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 Strange faults
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 Return to top of page · Post #: 1 · Written at 1:07:18 AM on 27 December 2024.
Marcc's avatar
 Marcc
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 5498

Today, working the graveyard shift to escape the heat (over 40), I got the second ever weird mechanical valve fault. The first one was a 6D6 where the envelope fell out of its base when the set was inverted: Not soldered.

Todays was a 6U7, a cantankerous tube at the best of times. Set (Howard) was having intermittent issues with this tube. Its socket was damaged to the point of replacement, but was not the actual problem, the actual issue was once again a pin. Pin 5 of the 6U7 had not been soldered?
 
 Return to top of page · Post #: 2 · Written at 8:13:02 AM on 27 December 2024.
Johnny's avatar
 Johnny
 Location: Hobart, TAS
 Member since 31 July 2016
 Member #: 1959
 Postcount: 575

Kriesler TV's had a similar problem at one stage.

It was found after some time that female workers during their monthly cycle imparted an acid from their fingers onto the filament loop of the EHT rectifier.
The solder joint after many months became dry as if never soldered.

I have seen similar effects in very old valves as you describe.
Corrosion of some sort with the solder/wire used at the time of assembly.
JJ
 
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