Re-checked ALL electrolytics for values and polarity and they are OK; (other then some are higher voltage). Checked the tone control board for voltage, (term.#4) and it is OK (37.5V). On powering, terminals #1, 3, 5, 7 read 18.5V and slowly recede to 0 volts. At turn off the voltage jumps to 16.5V and then slowly recedes to 0 vots. Noticed: higher the volume, louder the pop at turn off (main power).
audible pop in pioneer sx-950
- Thread starter karel.b
- Start date
Hi - excuse me for butting in here, but karel.b could you please confirm which switch is causing the noise? It seems that things got a little turned around here and I wonder if everyone is talking about the same symptom now. Is it making noise when the tone bypass switch is operated or is it making noise when the main power switch is operated? Thanks
Artie
Super Member
Cool. That gets us closer to the problem. The next thing I'd check is pins 12 & 21 of the "Flat Amp" assy. (AWG-038). Thats the input and output pins of the left channel. No real need to check both channels at this point.
If the problem is on 21, but not 12, then the problem is on that board. We can go from there when you check that.
The other option, and its not a bad one, is just always turn the unit on, go mix your martini, then come back to listen to music. But it is always nice to actually fix the problem.
Audiojones; Yes, we are talking about both switches, main ON/OFF(pops when turned OFF, gets louder with main volume icreased) and tone amp ON/OFF switch, which pops only right after the main is turned ON. Hope it will make some sense. Thanks
Artie,
I have to apologize for the testing I'd done is no good, because the meter I used (20 years to date) is totally inaccurate, which I found out this morning. So I went and bought a Fluke digital multimeter. It suppose to be fairly accurate. I tested the two board again and have the results. Voltage on all pins of both board reseds to zero after reaching maximum. Voltage on some pins varies, depending on tone control switch being ON or OFF. TONE AMP in by-pass mode (switch OFF): Power ON = pins #1, 3, 5, 7 are +6.3V; Power OFF = pins #1, 3, 5, 7 are -4.8V. Tone amp engaged (switch ON): Power ON = pins #1, 3 are +8.9V, pins #5, 7 are +2.2V; Power OFF = pins #1, 3 are -7.2V, pins #5, 7 are -1.9V;
FLAT AMP with tone amp switch OFF: Power ON = pins # 11, 12 are +4.8V, pins # 19, 21 are +6.3V; Power OFF = pins # 11, 12 are -1.2V, pins # 19, 21 are -4.8V;
FLAT AMP with tone amp switch ON : Power ON = pins # 11, 12 are +4.8V, pins # 19, 21 are +9.0V; Power OFF = pins # 11, 12 are -1.2V, pins # 19, 21 are -7.2V;
I hope you can make heads or tails out of all this.
If I ever fix this receiver, I'll have more then just one martini. And I dont even know how I'll be able to thank you.
Artie,
I have to apologize for the testing I'd done is no good, because the meter I used (20 years to date) is totally inaccurate, which I found out this morning. So I went and bought a Fluke digital multimeter. It suppose to be fairly accurate. I tested the two board again and have the results. Voltage on all pins of both board reseds to zero after reaching maximum. Voltage on some pins varies, depending on tone control switch being ON or OFF. TONE AMP in by-pass mode (switch OFF): Power ON = pins #1, 3, 5, 7 are +6.3V; Power OFF = pins #1, 3, 5, 7 are -4.8V. Tone amp engaged (switch ON): Power ON = pins #1, 3 are +8.9V, pins #5, 7 are +2.2V; Power OFF = pins #1, 3 are -7.2V, pins #5, 7 are -1.9V;
FLAT AMP with tone amp switch OFF: Power ON = pins # 11, 12 are +4.8V, pins # 19, 21 are +6.3V; Power OFF = pins # 11, 12 are -1.2V, pins # 19, 21 are -4.8V;
FLAT AMP with tone amp switch ON : Power ON = pins # 11, 12 are +4.8V, pins # 19, 21 are +9.0V; Power OFF = pins # 11, 12 are -1.2V, pins # 19, 21 are -7.2V;
I hope you can make heads or tails out of all this.
If I ever fix this receiver, I'll have more then just one martini. And I dont even know how I'll be able to thank you.
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Hi guys,
I think I may have found the problem. Going over the boards with a magnifying glass, I found a small crack on the power supply ass'y, that put the C10 (470uF, 80V) cap out of commission. I took the cap right out and nothing changed, the receiver is doing same as it was before. I orderd a new board, so when I put it together, I'll let you know how it performes.
Thank you all
BTW, Artie was right on the money the first time, when he wrote that it may be one of the power supply rails coming on too slow!
I think I may have found the problem. Going over the boards with a magnifying glass, I found a small crack on the power supply ass'y, that put the C10 (470uF, 80V) cap out of commission. I took the cap right out and nothing changed, the receiver is doing same as it was before. I orderd a new board, so when I put it together, I'll let you know how it performes.
Thank you all
BTW, Artie was right on the money the first time, when he wrote that it may be one of the power supply rails coming on too slow!
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I received the POWER SUPPLY ASS'Y board (AWR-101) today. It is brand new, but who knows when it was made. The supplier told me that I should have no problem using it the way it is. But I have some reservation about the use of new (but old) electrolytic caps, especially in the power supply. Could anyone help me with this issue? I would appreciate any input from you guys.
Thanks
Thanks
The board was warped due overheating before I re-built it. Some of the copper was coming off the board. Also there was that crack, as I pointed out before. I did the best I could to fix it. When I found a new one on Ebay it was a blessing. So, the only thing I have to do (or not) is to change the caps. Like I said before, the board is new, but old stock.
Changed the power supply board and no positive results. And top it all off, it is running hot. Replaced all the electrolytics (from the old board, they were new when I fixed it ), no change. The only thing I noticed, that the markings on Q1, Q2, Q8, Q9 are different. Q1 is D313D (was D313E), Q2 is B507D (was B507E), Q8 is D313E (was D313D), Q9 is D313D (this one is the same). And they are the ones that are running hot. The pop is still there, no change. I'm running out of options, other than take it to a repair shop, something I realy dont want to do. Any ideas? Anybody? I had ARTIE helping me, but I have not heard from him for a while. Did I do anything wrong? BTW; what is the difference between the "E" and "D", if any? Looking at the parts list Q1 is 2SD313P-E and Q2 is 2SB507P-E, Q8, Q9 are 2SD313-E. Are these markings made to confuse all none-professionals?
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Hey, it IS a hard problem, years ago my boss had to tell me to quit working on a different Pioneer (older) for that exact type of problem.I was just getting to T'd off because i was hell bent on fixing it. (well after quiting time no pay)
Thinking now I just cannot remember if I fixed it or not, I must have fixed it or I think I would still be pissed off.
All i can tell you it's a voltage imbalance coming from the tone board, you or the new caps did something, I think you said it used to work.
My best guess it is some small cap, or bad connection on the tone amp board or in that area.
The supply that runs hot, they do run hot but I can't tell online if it is normal or not.
Best thing is to step away, and tackle the tone amp board later.
All i ever cared about the letters, was get the same or higher, but it is essentially the same transistor.
Thinking now I just cannot remember if I fixed it or not, I must have fixed it or I think I would still be pissed off.
All i can tell you it's a voltage imbalance coming from the tone board, you or the new caps did something, I think you said it used to work.
My best guess it is some small cap, or bad connection on the tone amp board or in that area.
The supply that runs hot, they do run hot but I can't tell online if it is normal or not.
Best thing is to step away, and tackle the tone amp board later.
All i ever cared about the letters, was get the same or higher, but it is essentially the same transistor.
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pop in pioneer sx-950
After much wasted time trying to fix the receiver on my own, I took it to a repairman that specializes in vintage stereos. After 2 weeks I received a call from him, that he has no clue where the pop is coming from. He also told me , that he could not find anything wrong with the work I've done. The only thing he pointed out, that the tone amp had 10 tantalum caps that I replaced with Nichicon UKL (low leak) caps. Small difference in leakage: CSZA (tantalum)= 0.002CV, UKLs = 0.003CV. His suggestion : replace the UKLs with tantalum as originally supplied from Pioneer. So, that will be the last thing I'll try and if it does not work I'll sell it on Ebay for parts. I'll most likely regret it later, but that is how I feel now.
After much wasted time trying to fix the receiver on my own, I took it to a repairman that specializes in vintage stereos. After 2 weeks I received a call from him, that he has no clue where the pop is coming from. He also told me , that he could not find anything wrong with the work I've done. The only thing he pointed out, that the tone amp had 10 tantalum caps that I replaced with Nichicon UKL (low leak) caps. Small difference in leakage: CSZA (tantalum)= 0.002CV, UKLs = 0.003CV. His suggestion : replace the UKLs with tantalum as originally supplied from Pioneer. So, that will be the last thing I'll try and if it does not work I'll sell it on Ebay for parts. I'll most likely regret it later, but that is how I feel now.
I am told 'Noisy transistors" I had some in my sx950 sometimes a muffled pop or a sharp pop. MY SX850 at times would sound great then I'd lose
one side, right side. I turned rcvr off for say half to an hour, then back on, The rcvr would work very well for a while, so it depends I guess on volume
setting and maybe some dust not allowing sufficient cooling.