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SX-1250 suddenly dead

Robayb

Robayb

Active Member
All of a sudden my Pioneer SX-1250 is dead. The lights for the selectors are all dead, the lights for the speaker selection are all dead. The FM radio signal is dead, the meter does not move when flipping through the channels. The only thing working is the main panel lights. Its not in protection mode. Does this sound familiar to anyone??? Hopefully not a catostraphic failure. Seems wierd that selector lights and sound are all of a sudden dead together.
 
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sounds like you lost the 13.5v regulated DC. It is supplied by the stabelizer board. Usually the TO220 Q9 transistor open base-emitter, or gets leaky and causes the 3.9 ohm resistor R17 to open. Easy way to check is to measue the DC on the collector of Q9 (heat sink and look for 20 volts. You should then check pin 9 of that board for 13.5v (or pin 15 on the AM/FM IF and MPX board which may be easier to get to. The 5.4v DC for the indicator lamps requires the 13.5 to be working. If the transistor is open, you will probably see 23v dc or a little more on the collector as its not conducting. If you see 0 volts on the collector, look to see if the resistor is open, or see if you are missing the 23v in on pin 7 of the stabelizer board.
But always first thing is to check for blown fuses, although I don't think this is causing your problem.
If your problem is on the regulator board, make sure to check the other transistors in the 13.5 volt circuit, especially transistors, zener diodes, rectifiers, and look for leaky capacitors as well.
 
Tom B said:
sounds like you lost the 13.5v regulated DC. It is supplied by the stabelizer board. Usually the TO220 Q9 transistor open base-emitter, or gets leaky and causes the 3.9 ohm resistor R17 to open. Easy way to check is to measue the DC on the collector of Q9 (heat sink and look for 20 volts. You should then check pin 9 of that board for 13.5v (or pin 15 on the AM/FM IF and MPX board which may be easier to get to. The 5.4v DC for the indicator lamps requires the 13.5 to be working. If the transistor is open, you will probably see 23v dc or a little more on the collector as its not conducting. If you see 0 volts on the collector, look to see if the resistor is open, or see if you are missing the 23v in on pin 7 of the stabelizer board.
But always first thing is to check for blown fuses, although I don't think this is causing your problem.
If your problem is on the regulator board, make sure to check the other transistors in the 13.5 volt circuit, especially transistors, zener diodes, rectifiers, and look for leaky capacitors as well.
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Thanks alot
 
I was going to post a link to that thread soon as I saw your symptoms, but Tom beat me to it. Note, I replaced a blown fuse and the receiver has been playing daily for a couple months now with no problems. You may have other issues though if it's original. Mine was completely gone through and a lot of those trouble spots were replaced/upgraded. Hope you get it sorted out.
 
And to improve reliability, get it restored. It takes a lot of risk away from using vintage gear. The key is to get it done by a reliable tech. Even better, an artist. :D
 
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