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Old 26th Feb 2006, 3:05 pm   #5
Jim - G4MEZ
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Join Date: Feb 2006
Location: Newport Pagnell, Buckinghamshire, UK.
Posts: 95
Default Re: Bush VHF54 FM Problems

I have the same problem on my VHF64. +27V across the discriminator reservoir etc. I found that if the VHF and MW (or LW but not SW) keys are held down simultaneously it bursts into life on VHF. As far as I can see, doing this removes the 27V of VHF AGC from the second IF amp and tames it down a bit, perhaps stopping it from taking off.

Not sure if you can play the same trick on other Bush VHF series as an aid to fault-finding but loading down the anodes of the IF Amps with a highish value resistor (or even an AVO) will damp it down.

I'm off to change all the decouplers around the IF stages and see if it cures it.

Jim
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