Hello!
I have unusual problem with the Sony PS-X45: when powered on it immediately starts to spin the platter backwards. When I press start - it starts in right direction, holds the speed, all the buttons and indicators works as they should. Even the crystal lock works fine. But when stopped it starts to spin back again until powered off.
I have a service manual (schematics attached) and a scope, but unfortunately have almost no experience at fixing electronics of that level of complexity.
Full service manual is available here: SONY PS-X45 Service Manual download, schematics, eeprom, repair info for electronics experts
So, do you have any thoughts where to start digging?
I have unusual problem with the Sony PS-X45: when powered on it immediately starts to spin the platter backwards. When I press start - it starts in right direction, holds the speed, all the buttons and indicators works as they should. Even the crystal lock works fine. But when stopped it starts to spin back again until powered off.
I have a service manual (schematics attached) and a scope, but unfortunately have almost no experience at fixing electronics of that level of complexity.
Full service manual is available here: SONY PS-X45 Service Manual download, schematics, eeprom, repair info for electronics experts
So, do you have any thoughts where to start digging?
Attachments
Try and clean and adjust your 2 offset potentiometers RV104 & RV105, or look for errors around this circuit.
it probably spins the motor in reverse to brake the platter when finished playing. There may be a "parking brake" belt that is worn.
Rv104 and RV105 may need adjustment as the 4558 based motor driver can provide reverse polarity to the motor.
Rv104 and RV105 may need adjustment as the 4558 based motor driver can provide reverse polarity to the motor.
Hmm... I was sure that if the motor runs correctly in the play mode then offset is ok. And yes, I have constant negative output on pin 1 of the IC102 DC motor controller in stop mode.
Thank you all for your advice. I have some not very good news.
I tried to adjust gain/offset as you recommended using the guide from the manual (pic attached).
At the point 2 I have no AC voltage except some high frequency noise and about -1.5V DC on pin 1 of IC102. Adjusting the 50K resistor has almost no effect on voltage. The backward rotation slows a bit when I connect that shunt but does not stop.
However, I tried to adjust all the RVs mentioned and got something very close to the values in the manual, but with no significant positive effect - it still rotates backwards (a bit slower although) and accelerates when I remove the shunt...
So, what do you think should I try next?
I tried to adjust gain/offset as you recommended using the guide from the manual (pic attached).
At the point 2 I have no AC voltage except some high frequency noise and about -1.5V DC on pin 1 of IC102. Adjusting the 50K resistor has almost no effect on voltage. The backward rotation slows a bit when I connect that shunt but does not stop.
However, I tried to adjust all the RVs mentioned and got something very close to the values in the manual, but with no significant positive effect - it still rotates backwards (a bit slower although) and accelerates when I remove the shunt...
So, what do you think should I try next?
Attachments
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