Hi all,
I have performed the service bulletin modifications on mine and have a strange issue with the voltage on the collector of the negative regulator pass transistor.
I’m getting +/- 36 volts in to the board ( NB+ & NB- ) and see the raw +38v DC on the collector of the positive regulator pass transistor, as well as the expected 100hz ripple.
On the collector of the negative pass transistor I measure about 28 volts and see no ripple.
The power supply is supposed to put out +/- 25 volts and puts out +/- 26.3 V.
I recapped it as well as installing TIP41Cs in the place of the original SD234 ( TR712 and TR715) pass transistors but am a bit worried about this strange result, any ideas?
Service manual is here: https://www.vintageshifi.com/repertoire-pdf/pdf/telecharge.php?pdf=Yamaha-CR-2020-Service-Manual.pdf
Many thanks,
I have performed the service bulletin modifications on mine and have a strange issue with the voltage on the collector of the negative regulator pass transistor.
I’m getting +/- 36 volts in to the board ( NB+ & NB- ) and see the raw +38v DC on the collector of the positive regulator pass transistor, as well as the expected 100hz ripple.
On the collector of the negative pass transistor I measure about 28 volts and see no ripple.
The power supply is supposed to put out +/- 25 volts and puts out +/- 26.3 V.
I recapped it as well as installing TIP41Cs in the place of the original SD234 ( TR712 and TR715) pass transistors but am a bit worried about this strange result, any ideas?
Service manual is here: https://www.vintageshifi.com/repertoire-pdf/pdf/telecharge.php?pdf=Yamaha-CR-2020-Service-Manual.pdf
Many thanks,
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Its quasi-complementary, one side is darlington, the other CFP, the emitter of TR715 corresponds to the collector of TR712.
Thank you Mark.
So it sounds like the voltage and lack of ripple are correct.
Is there some sort of reference I could read up in this further, it’s not the first linear power supply that has me confused and searching the web seems to mainly reference simpler designs?
So it sounds like the voltage and lack of ripple are correct.
Is there some sort of reference I could read up in this further, it’s not the first linear power supply that has me confused and searching the web seems to mainly reference simpler designs?