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Old 8th May 2024, 1:33 pm   #1
Michael Maurice
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Default Pioneer SX-727 receiver

This receiver had some unwanted attention from its owner.

The RH O/P stage had failed and instead of the output being at 0V it sat at around 17V.

The original transistors are no longer available, so I fitted BC237's as the input long tail pair, BD829/830 for the driver stage and 2SC1586 / 2SA909 for the output pair.

However it would seem that the output pair are not being driven correctly because as soon as you put a load onto it, there is terrible distortion. There is also no voltage across the output transistors emitter resistors.

So is it the drivers or the O/P transistors.

If i need to change them then I could use BD911 / 912 for the drivers and 2N3773 / 2N6609 for the outputs. ?

Any thoughts
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Old 14th May 2024, 9:56 am   #2
PJC58-Hythe
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Default Re: Pioneer SX-727 receiver

If you have fitted BC237's in place of the 2SA572's then you have fitted NPN instead of PNP - KSA992's would be a good substitute.
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Old 14th May 2024, 10:21 am   #3
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Default Re: Pioneer SX-727 receiver

Quote:
Originally Posted by Michael Maurice View Post
This receiver had some unwanted attention from its owner.

The RH O/P stage had failed and instead of the output being at 0V it sat at around 17V.

The original transistors are no longer available, so I fitted BC237's as the input long tail pair, BD829/830 for the driver stage and 2SC1586 / 2SA909 for the output pair.

However it would seem that the output pair are not being driven correctly because as soon as you put a load onto it, there is terrible distortion. There is also no voltage across the output transistors emitter resistors.

So is it the drivers or the O/P transistors.

If i need to change them then I could use BD911 / 912 for the drivers and 2N3773 / 2N6609 for the outputs. ?

Any thoughts
Did you mean BC327 ?
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Old 15th May 2024, 11:10 am   #4
Michael Maurice
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Default Re: Pioneer SX-727 receiver

Quote:
Originally Posted by FIXITNOW View Post

Did you mean BC327 ?
Yes my mistake BC327!
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