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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

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Old 7th Apr 2018, 11:52 pm   #1
Michael Maurice
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Join Date: Feb 2006
Location: Wembley, Middlesex
Posts: 5,695
Default Bush SRG91

I've just finished repairing the radio chassis from this radiogram and had some very off faults.

When I got it the ECC83 had gone to air, so after a recap and replacing of some resistors, I found R50 was smoking, this was because one of the EL84's was taking grid current, ie the grid voltage was positive and the cathode was at 14 volts rather than 6-7 volts.

Next I couldn't get FM, and I found a hunts capacitor C39 lurking around the switch bank, I replaced it and I got FM.

The most surprising thing I found was that the grid of the ECH81 was also positive, so I removed it and the grid voltage dropped to 0V, so I replaced it and the grid voltage remained at 0V.

I supposed any valve can run into grid current though I thought it only power valves that this happened to.
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Old 13th Apr 2018, 2:23 pm   #2
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Join Date: Jun 2012
Location: Milton Keynes, Buckinghamshire, UK.
Posts: 100
Default Re: Bush SRG91

I remember this model very well, we sold quite a few in the early days.
it was always a favourite and performed very well.
Wish I had house room for one.
The only problem we had were the coupling capacitors to the output stage.
(that capacitor)
Hope all works out well for you
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