Pioneer SX-1000TD left channel dead after re-cap

iplagolf

Well-Known Member
Hello...Posted a while back about this receiver. Life got in the way, yada, yada...I re-capped it and changed some problematic transistors. I checked the voltages on the boards today (see pic's) they seen ok, on the power supply board the output pin 5 says 78V (64V) got 82V, pin 6, 35V have 41.0V, pin 8 125V have -0.060 and pin 11, 23V have -0.060V. Now on pins 9 and 10 on the input for the board the readings are the same. I'm lost about this. Everything else looks good. I'm starting the hunt board by board to trace the signal with my multimeter and Rigol DS1054Z oscilloscope (what a learning curve that was and it's still smarter than I am). I've checked the boards for mistakes, caps put in backwards or a cold solder joint(s), I've checked a half dozen times and have found nothing. It's been a while since I've used a solid state receiver, is there supposed to be a click after it's turned on or not? I'm referring to the circuit protection. There is no click but the slightest pop in the working channel. I've looked for the circuit protection on the schematic, not sure what it is or where it's located. I'm splashing around in the deep end of the pool and learning a lot. If you've worked on one or have any ideas or input please let me know. Thank you.
 

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pin 8 is supposed to be 12.5 vdc, and pin 11 should be 23 vdc. Pin 9 to pin 10 should read 25-30v AC. pin 9 to ground should be ~15vac and pin 10 to ground should be ~15vac. (remember to switch meter to read either the DC voltage or the AC voltage.

If you are getting the proper AC voltage (which you should) fine. Make sure the grey wire from the transformer is connected to a ground point.
Check for 23 volts DC at the point where the 2 rectifier connections (Cathodes of D305 and D306) connect also to the positive connection of C304 (200uf) Make sure this cap isn't reversed. Look closely there for damaged foil connections as you probably had replaced that cap. If you can't see DC at that point, and the connections look good, the 2 rectifiers (D305 and D306 ) may be bad. If the 23vdc is missing, you won't be able to get the 12.5 vdc either.
 
Hello...Went back through the power supply board today all my readings match yours. Since I have one channel working would that suggest the PS board is good, it's a mono board so to say, no right or left? The numbers you mention D305 and D306, on my schematic I find a D905 and D906 some of the 9's look like 3's. I checked the voltages at D905/06 and found 22.6vdc at each. At C904 on the + side I have 22.6 vdc. If I couldn't blow it up on the computer I'd be in real trouble. Thank you, Fritz
 
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Hello...Here are the readings on the caps from the main amp board. The readings are mirror images of each other. I believe on C811/812 need to be measured in Millivolts, I'll re-check that tomorrow as will read the other boards. I do have a question, the negative side of C813/814 is 37.0 VDC, why so high? Thanks, Fritz
 

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