John Bowers Active Control Unit preamp: Info sought - Page 3 - diyAudio
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Old 28th October 2013, 07:49 AM   #21
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managed to work it out thanks.

12VDC relay was supposed to be in fact a 6VDC. When one pole was 13.8VDC the other was 7.4VDC. with a diode across the coil cathode end at the 13.VDC terminal, leaving a 6.4VDC difference to power a 6 VDC coil. workaround for the 12VDC relay is to send an earth the 7.4VDC pole and disengage the 7.4 supply by removing a resistor.

One day I will replace the relay with a 6VDC and remove the makeshift earth.

Reason why I was getting low voltages to the op-amps was that the 15AC powerpac it came with had no earth.
Solution: install a 12-0-12 transformer and the other circuits become active!! 12/13 VDC to each of pins 1 and 8 on every opamp
all good!!

Many thanks for taking me back to basics

cheers
Andrew
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Old 28th October 2013, 07:52 AM   #22
Mooly is online now Mooly  United Kingdom
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Great to hear you figured it out

Its definitely one of those things you need in front of you to visualise what's going on.
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