Need help with wiring on Power supply and Protection Board Pioneer SX-850

daveyh

AK Subscriber
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I am working on a Pioneer SX-850 and it has been worked on before. Upon removing the bottom cover all the boards lost their plastic stays and look like it overheated them until they become brittle and broke. The person who worked on this tried to fix the board by gluing them to the broken stays and didn't do a very good job. I since then have removed the plastic broke one and replaced them with new ones.

The unit has a wire off the pin # 10 from the protection board and i have no idea where it goes. I have checked the service manual but need someone to help me. Does someone have an actual picture a good HD closeup they can post?

Also it look like #13 off of the protection board has been soldered to the post.
 
Forgot the picture. The unit comes on for and plays for around ten minutes in both channels and then no sound. This is what I found so far.
 

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You can download the service manual from HiFi Engine and trace to see where pin 10 goes from the schematic. Those wires can break off once the board is flipped to access the bottom of it.
 
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Got it from the video BlueGlow electronics posted on YouTube. Thank you for your input.

Now can't get to stop the relay from clicking in and out. Or on and off. :mad:

First there is sound and then there is not, sound and then there is not, sound and then there is not.
 
Issues with protection board or power supply.. First set the DC offset and idle current as mentioned in the service manual
 
Got it from the video BlueGlow electronics posted on YouTube. Thank you for your input.

Now can't get to stop the relay from clicking in and out. Or on and off. :mad:

First there is sound and then there is not, sound and then there is not, sound and then there is not.

Rebuild the protection board with all new transistors. Plenty of post for transistors to use.

Recommend full treatment of the power supply board too.

Have rebuilt the SX850 and SX950 following recommendation of others.

http://audiokarma.org/forums/index.php?threads/project-sx-950.850960/
 
I can not set the DC offset because the relay will not stay engaged. I am going to rebuild the PS and PB and see if it will help things.
 
I can not set the DC offset because the relay will not stay engaged. I am going to rebuild the PS and PB and see if it will help things.
You can measure DC offset on the power amp (AWH-059) board pins before the relay, instead of at the speaker connection. It is pin 10 for the left channel, pin 25 for the right channel. No speakers should be connected while doing this.
 
Also those broken plastic standoffs are available, I’ve seen them discussed here before - search around.
I’ve had several SX-850’s and now an SX-950 as my smaller bedroom systems - they’re outstanding receivers.
 
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