I picked up a Pioneer SX-737 the other day that has some issues. The seller described the issue as "plays good for a few minutes and then its like the antenna stops picking up". From reading other threads in this forum I asssumed it was having some protection circuit issues, so I took the chance. When I got it home I cleaned all of the switches and pots with deoxit, and then powered it up to see what happened. Sure enough the relay would open up after a minute or so and it would sometimes toggle back and forth a few times before ultimately staying open. I checked the DC offset and it was very high especially in the right channel.
I found the corrected bias and DC offset procedure here on the forum and gave that a shot. I was able to get the offset down in both channels, but the adjustment pots did not provide enough adjustment to get things dialed down to 0 in both channels. I was able to get the protection circuit to stop cutting things out however.
At this point the left channel is down around 0, but it does swing around a bit. Every once in awhile it will just run away to up around a half a volt. It usually will come back down after a few seconds, then it runs away again.
The right channel seems to be stuck around -.2 volts. It also seems to swing around as well. Fine adjustment on this channel does not seem possible.
I have found the recap parts list for this receiver, and I am planning to go ahead and order all of the parts to have on hand. I would like to go ahead and replace all of the parts on the list, but I am hoping that I can get it working correctly first rather than just taking the shotgun approach and replacing everything.
Any advice on next steps would be greatly appreciated. I have been reading the service manual, and I do have the voltage readings from several of the boards that I can provide. I am new to this hobby, but would really like to expand my knowledge. If I can also end up with a nice SX-737 in the end then that would also be a bonus.
I found the corrected bias and DC offset procedure here on the forum and gave that a shot. I was able to get the offset down in both channels, but the adjustment pots did not provide enough adjustment to get things dialed down to 0 in both channels. I was able to get the protection circuit to stop cutting things out however.
At this point the left channel is down around 0, but it does swing around a bit. Every once in awhile it will just run away to up around a half a volt. It usually will come back down after a few seconds, then it runs away again.
The right channel seems to be stuck around -.2 volts. It also seems to swing around as well. Fine adjustment on this channel does not seem possible.
I have found the recap parts list for this receiver, and I am planning to go ahead and order all of the parts to have on hand. I would like to go ahead and replace all of the parts on the list, but I am hoping that I can get it working correctly first rather than just taking the shotgun approach and replacing everything.
Any advice on next steps would be greatly appreciated. I have been reading the service manual, and I do have the voltage readings from several of the boards that I can provide. I am new to this hobby, but would really like to expand my knowledge. If I can also end up with a nice SX-737 in the end then that would also be a bonus.
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