AC30 - I think this valve is U/s

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AC30 - I think this valve is U/s

Postby SJB » Fri Apr 14, 2017 12:21 pm

I recently looked at a Rose Morris era AC30 which had gone dead.

On removing the chassis I noted the PSU 10 Ohm resistor was on the bottom of the case.
Seems it had soldered itself. The resistor was still usable - although I did change it.

I think this is the culprit :-
6BQ5 with hole blown in the anode a.jpg
6BQ5 with hole blown in the anode a.jpg (398.87 KiB) Viewed 689 times


Opening up the Vavle we see the flash-over occurred from the Cathode to the Anode taking out grids on the way.

6BQ5 with hole blown in the anode a.jpg
6BQ5 with hole blown in the anode a.jpg (398.87 KiB) Viewed 689 times


This AC30 does not have a 500mA fuse in the HT.
All is now well again. Been on soak test for hours.

Not sure if the valve glass fractured first. Current must have been there for a while to de solder the resistor.
So on re-fitting the fuse I have not wrapped the resistor ends around the tags - seems we need a fuse sometimes.

SJB
Attachments
6BQ5 with hole blown in the anode - 3.jpg
6BQ5 with hole blown in the anode - 3.jpg (317.34 KiB) Viewed 689 times
SJB
South Coast Shadows, Surrey Shadows,
South Wales Shadows,
SJB
 
Posts: 78
Joined: Tue Jan 06, 2015 12:50 pm
Location: Hampshire
Full Real Name: Stuart J Best

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