SX 939 roadside find

PK007red

PK007red

New Member
IMG_7257.JPG Team,
I need help on a SX-939 roadside find. It was sitting half in a box with snow on it. I saw the wooden case and sure enough, vintage audio. Now I figured it was a toast but I hauled it home anyway. I dried it out for a day with a fan on it and gave it a try. It lit up nice and I could hear the protection circuit click, good news but no sound. Just some crackle when I messed with the knobs. I Deoxed it and it sounds great. But I found something odd. On the FM board, there is one wire that looks cut, it makes no sence because I have no idea why someone would do this and I don't thinks this could just separate on its own. Was this some sort of factory setting where it's cut for certain markets or it disables part of a board that is used in several models? Should I repair this wire? See pic.

I did try the FM radio without a antenna and didn't get anything, but that is common at my house.
 
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Those "may" be test points.
Pioneer did that in places. Left short wires sticking out to be used by service techs.

Just a guess.
 
THAT wire is on the tuner board and it has been discussed in previous posts. It connects pins 7 (mpx out) and pins 31 (mpx in) for the initial setup of the tuner at the factory, it BYPASSES the awm-063 muting circuit assembly - which would otherwise block the signal to the stereo decoder when the muting level is set initially too high - this would prevent setting the stereo decoder up. Once the muting level is correct, the mute circuit functions properly and the link is cut to send signal to the muting circuit to be sure the mute circuit DOES mute a weak stereo signal.

So, leave it alone.
 
markthefixer said:
THAT wire is on the tuner board and it has been discussed in previous posts. It connects pins 7 (mpx out) and pins 31 (mpx in) for the initial setup of the tuner at the factory, it BYPASSES the awm-063 muting circuit assembly - which would otherwise block the signal to the stereo decoder when the muting level is set initially too high - this would prevent setting the stereo decoder up. Once the muting level is correct, the mute circuit functions properly and the link is cut to send signal to the muting circuit to be sure the mute circuit DOES mute a weak stereo signal.

So, leave it alone.
Click to expand...
I like your sig... so true ;)
 
PK007red said:
View attachment 847133 Team,
I need help on a SX-939 roadside find. It was sitting half in a box with snow on it. I saw the wooden case and sure enough, vintage audio. Now I figured it was a toast but I hauled it home anyway. I dried it out for a day with a fan on it and gave it a try. It lit up nice and I could hear the protection circuit click, good news but no sound. Just some crackle when I messed with the knobs. I Deoxed it and it sounds great. But I found something odd. On the FM board, there is one wire that looks cut, it makes no sence because I have no idea why someone would do this and I don't thinks this could just separate on its own. Was this some sort of factory setting where it's cut for certain markets or it disables part of a board that is used in several models? Should I repair this wire? See pic.

I did try the FM radio without a antenna and didn't get anything, but that is common at my house.
Click to expand...
Good luck with the 939! I use the 9930 (939 blackfaced twin) and couldn't be happier :thumbsup:
 
markthefixer said:
THAT wire is on the tuner board and it has been discussed in previous posts. It connects pins 7 (mpx out) and pins 31 (mpx in) for the initial setup of the tuner at the factory, it BYPASSES the awm-063 muting circuit assembly - which would otherwise block the signal to the stereo decoder when the muting level is set initially too high - this would prevent setting the stereo decoder up. Once the muting level is correct, the mute circuit functions properly and the link is cut to send signal to the muting circuit to be sure the mute circuit DOES mute a weak stereo signal.

So, leave it alone.
Click to expand...
Great news,

It looked like to easy of a fix that it just made me question if it was intentional.

Thanks
 
Why can't I ever make these kinds of finds, you are a lucky guy the 939 is a great receiver when working properly, Congrats!
 
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