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Old 22nd Apr 2017, 1:21 pm   #6
Chicoull
Triode
 
Join Date: Dec 2016
Location: Elgin, Moray, UK.
Posts: 31
Default Re: Bush DAC 90A Conversion

Before breaking into my restored Bush, I opened up an unrestored 90A this morning and disconnected the input to the volume switch - without connecting the Bluetooth.

The second radio has the same issue - a tuneable radio signal with fixed volume at the speaker. So, two radios - one fully restored with replacement valves, new caps, resistors and wiring - versus an untouched original.

The same issue in both suggests that the stray signal is in the design so I will revisit the circuit diagram - try and trace the route and attempt a block - possibly additional decoupling as suggested.

As to the Bluetooth output - it is stereo, so I have a couple of 1k resistors tied together to give a mono output and a 10k resistor across the output for a load.
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