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Old 28th Oct 2020, 5:45 pm   #55
DMcMahon
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Join Date: Apr 2019
Location: Worthing, West Sussex, UK.
Posts: 6,587
Default Re: Vortexion reel to reel tape recorder WVA series 5

If the components around the 12BH7 check out OK and you are happy that the valve is good, then I wonder if the bridge rectifier may have a partial fault and be dragging/reducing down the bias signal seen by the meter.

If you have a scope then check the bias signal at the Set Bias pot area and make sure it is a clean and stable sinewave and note its amplitude, the manual indicates frequency will be around 58kHz.
Also check the rectified signal going to the meter.
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