I have a pioneer sx-727 receiver, I'm the original owner (33 years). Recently the radio stopped working. Everything else works great. FM, AM no difference does NOT work. The tuning meter does not move as I turn the tuning dial. If I turn the volume up, I can hear some static thru the speakers. Occasionally the radio will spontaneously work for a while, and then return to this dead mode. All the other inputs cd, turntable work fine. Any ideas what the problem might be? Thanks.
Sounds like something is intermittent in the radio section (assumes amplifier/auxiliary input/tape/etc. all are still working fine). I'd start by looking for cold/broken solder connections under a magnifying. Or alternatively, if that does not work and you can get at the board safely while the unit is powered up, you can try pushing at various points with a wooden dowel or similar non-conductive item. This may help you isolate the area to take a closer look.
If these do not help, then you'll either need a schematic, a volt meter, scope, and some troubleshooting skills to check the power supply voltages at key points and then follow the signal through the radio section or take it to someone to do the work for you.
OK I took the thing apart and sure enough, there was a sanyo 313E mounted on a V shaped piece of metal(heatsink?). When I tapped gently on the metal, everything now works fine. The small board in question is AWR-011A, which according to the schematic is the power supply unit. I would think that if this was the roblem it would effect everything, not just the radio. Anyway I will run it for awhile with the case open, and see if the problem recurs.
It has been a long time, but I seem to remember a common problem of a voltage regulator in the power supply section becoming thermally/ mechanically/whateverly intermittent. If the entire tuner section is going dead, this might be worth looking for. Seems a reasonable candidate if the tuner works occasionally as you stated.
Look for a 3-pin voltage regulator in a TO-220 case - might not even be on a heatsink. Try tapping it with something non-conductive, or heating it, or freezing it, or, you might actually measure its output voltage. Worth a quick look, I suppose.
I have left the case open, and have the thing sitting on a shelf vertically. It worked flawlessly for about 3 days, then spontaneouslt the radio went dead again. I ever so gently tapped the heatsink that this transistor is on, and once again everything is fine. I have not lifted the board yet to look at the solder underneath. However I'm beginning to think that it is the transistor itself that is the problem. Can I find the exact replacement at radio shack? If I'm going to lift the board, I'm thinking it's probably makes sense to replace the device.
Just resolder the transistor. You will see that the solder connections there have ring cracks from age and heating / cooling over the course of time. Common problem.
I decided to lift the board and look at the solder for the device sanyo 313e. Before I could do anything the V shaped metal (heatsink?) attached to the device just fell off. The plastic screw holding it had just cracked in half. There also is a thin piece of plastic between the device and the heatsink. I'm assuming that they do want the device to touch the metal. I could not find a another plastic screw, so I use a metal one with an insulating washer. I hope that is ok. Why does the device need to be insulated from the metal heatsink. Is it strictly pecautionary, in case the heatsink comes in contact with something else. Would it be ok to put some cpu grease between the device and the plastic insulator? Anyway after all this the solder looked ok, so I did not resolder. I wonder if my problem all along was that the heatsink was just hanging on by a thread. Anyway it seems to work ok. I'll run it for a while with the case open as a precaution.
I decided to lift the board and look at the solder for the device sanyo 313e. Before I could do anything the V shaped metal (heatsink?) attached to the device just fell off. The plastic screw holding it had just cracked in half. There also is a thin piece of plastic between the device and the heatsink. I'm assuming that they do want the device to touch the metal. I could not find a another plastic screw, so I use a metal one with an insulating washer. I hope that is ok. Why does the device need to be insulated from the metal heatsink. Is it strictly pecautionary, in case the heatsink comes in contact with something else. Would it be ok to put some cpu grease between the device and the plastic insulator? Anyway after all this the solder looked ok, so I did not resolder. I wonder if my problem all along was that the heatsink was just hanging on by a thread. Anyway it seems to work ok. I'll run it for a while with the case open as a precaution.
insulating washer. I hope that is ok. Why does the device need to >be
as a precaution.
If the solder is really OK, which I doubt. Then the transistor is failing. On this TO-220 case transistor this most commonly happens from a base-emitter junction opening up internally.
If you were to look very closely at the solder connections ( I recommend a magnifying glass) I believe you will see the ring-cracks around the transistor leads.
In this particular case the heat sink has no other electrical connection, but you are still going to need another screw and nut. Another mica insulator and some silicon grease would be good, although as I say, in this case I think you could dispense with the mica.
Alternatively you could use a newer style TO-220PL plastic case transistor such as a 2SC4793 which requires no insulator.
It's unfortunate in a way that your skills and experience don't seem to quite be up to the task. I don't say that as a put-down, but this whole thing should have been over long ago.
If you decide to replace the transistor, you'll need a source for the part, and most suppliers have 15.00 to 20.00 minimum orders.
You might consider OEQuotefix to fix your problem with Outlook Express making messy looking posts. It's a free download.
No need to be nasty. The solder looked ok to me. The board is very old, so the plan is to proceed cautiously. I have attached the device properly to the heatsink. If the problem recurrs, I will reheat the solder joints. If that does not solve the problem then I will replace the device. I'm assuming that a 2sd613 will be an adequate replacement, correct?
No need to be nasty. The solder looked ok to me. The board is very old, so the plan is to proceed cautiously. I have attached the device properly to the heatsink. If the problem recurrs, I will reheat the solder joints. If that does not solve the problem then I will replace the device. I'm assuming that a 2sd613 will be an adequate replacement, correct?
***************************** A 2SD 613 would be fine.
I'm not sure why the > marks aren't showing in the quoted sections, I had to add them manually last time.
I don't feel I was being nasty before, even said so:
I was watching as several other responders were telling you to replace the transistor and a lot of back-and-forth when as I say this coulda / shoulda been over with long ago.
OK thanks sounds good. One more question. In the process of lifting the board to examine underneath, the plastic tabs that hold the board in place are very brittle. One broke and the others half broke off. Can I pull these out from the side that the power supply board is on? I'm thinking that mayb I can replace these with some computer mainboard ones that I have lying around?
Yes, if the area to be soldered can only be accessed by pulling the board up - it's been a long time since I've worked on a 727. I was thinking the board could be accessed from underneath.
Regarding: "If you decide to replace the transistor, you'll need a source for the part, and most suppliers have 15.00 to 20.00 minimum orders."
Consider:
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( "No order is too small." )
For the datasheet on a 2SD613:
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( click on, Click Here, at the page - make sure you have Adobe Reader )
Incidentally, Mouser does not have a minimum order however, they do not show stock on a 2SD613. Needless to say shipping has gone way up for *everyone.*
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At 1490 pages, Mouser [typically] has what you need. I don't doubt that they have an equivalent to the 2SD613 in stock. However, with the above actual transistors, you have alternatives.
Well just when I thought everything was fixed... The receiver had worked flawlessly for over 3 weeks. Then suddenly today the radio went dead again. I took it apart and this time reheated one of the solder joints on the questionable transistor (d313e). Anyway everything is back together and working. Hopefully this will permanently fix the problem. The plastic tabs that hold the board in place are disintegrating. Anybody know where I can get similar tabs? Thnaks.
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