Recapping SX-950

Yes. The VR1 and VR2 potentiometers are for adjusting the DC offset, VR3 and VR4 for bias. You can make your life a little easier by jamming your meter probes into the speaker outputs (making sure that whichever speaker group you choose is ON!) when setting the offset, rather than probing directly at the board.

I see, thank for the tip!
I am going to give this beauty a good cleaning today.
 
Help!

I put new caps on the power supply board in my sx-950 and when I turned it on to test the new caps it blew all 4 fuses on the power supply board. Any thoughts about why?
 
I put new caps on the power supply board in my sx-950 and when I turned it on to test the new caps it blew all 4 fuses on the power supply board. Any thoughts about why?

You should really start your own thread, then explain further about how and why you changed out the caps. Was it dead, was the protection not engaging?:scratch2::scratch2:
 
If I were to push this up a notch and use even better components, should this be possible and should there be any tangible benefit, where would I go.
Makers?
Performance?
Voltage?
Etc.
 
Pioneer ran their units "hot" or right at the upper limit of the SOA. Most of the Receivers I've seen from PIONEER have the Power supply on the bottom, facing down and the heat made is trapped. I'd replace all the transistors with modern equivalents that dissipate more heat, and are not affected as much by the heat generated. Also if you have the room upgrading or adding to the heatsinks will help.

Given that both these TO-220s ran very warm, I'm thinking this is what you may have had in mind:

PioneerSX-950PowerSupplyHeatSinks.jpg


They are lower (higher?) than the tallest E-cap on that board, and now have mica and insulating washer so the sinks aren't live.

The dual TO-220 array is also shrouded by the bottom cover, preventing any convection air from passing their heat sink. Measured heat on the stock heat sink was acceptable (I could hold my finger on it indefinitely) but there was concern over the shrouding. Extending the factory vent hole pattern to allow air under the area may not have been necessary, and I hope it doesn't negatively affect the air flow there.

PioneerSX-950BottomVentilation.jpg
 
667-ECQ-V1H224JL2 is not available on mouser anymore. I found on a forum for sx1050 that 505-MKS2C032201B00KS is a compatible alternative. Any opinions on this?
 
Also these guys are not available:

667-ECO-S1KP681BA
667-ECO-S1HA222BA

Just wondering if anyone has found good alternatives before I go searching.
 
Great thanks for the help.

For the big power supply caps I did a quick filter search on Mouser and found these:

Some candidates for the AWR-101 C10: 470uF 80v ACH-038 (previously 667-ECO-S1KP681BA)
598-81LX681M080J202 (probably this one?)
661-ELXG800VSN681MP2

For AWR-101 C12: 2200uF 35v ACH-039 (previously 667-ECO-S1HA222BA)
647-LKS1H222MESA

Any experience with these? Do they look acceptable?

Thanks
 
Couple more question

1. What do most people use for the main power caps (ACH-059 22000uF 63V; C1 and C2 from 'miscellaneous parts',). I have seen the big blue Nichicon used a lot, which I'm guessing is this: 647-LNR1K223MSE? However I have seen some people recommending something like this: 647-LKG2A681MESZCK from the KG series. Not sure what the benefit of using capacitors from the "high grade audio" category would be for these types of capacitors.

2. Related to this, just wondering what the overall stance on 'high grade audio' capacitors in general is for pioneers. I know this has been discussed extensively and there seem to be varying opinions. Most of the important caps on these lists use UKL series from Nichicon, which I know are good for the low leakage. Is this a better benefit than any of the high end audio capacitors can offer? Just wondering since I've never used them. Also, why are pioneer people so into Nichicons rather than Elna say. Price?
 
For the large filter caps I use whatever I can find that fits the clamps and is priced decent. Audio grade caps I am not going to go there I use them but really can not say I can hear a diffrence
 
For the large filter caps I use whatever I can find that fits the clamps and is priced decent. Audio grade caps I am not going to go there I use them but really can not say I can hear a diffrence

Yeah, I guess I've always found it hard to imagine there's really an audible difference. And looking at the spec sheets I don't see anything that looks very impressive or different. I know they are supposed to be made with different materials that somehow affect their behavior, but I have no idea what that means and I can't find much technical information about it. I think in high end audio there's always a lot of voodoo superstition that personally never seems to make a difference to me. Like 80 speaker wire classic example. But I'm still learning so who knows. I think on my next project I'll experiment with some high end caps and see if it really makes a difference...
 
Yeah, I guess I've always found it hard to imagine there's really an audible difference. And looking at the spec sheets I don't see anything that looks very impressive or different. I know they are supposed to be made with different materials that somehow affect their behavior, but I have no idea what that means and I can't find much technical information about it. I think in high end audio there's always a lot of voodoo superstition that personally never seems to make a difference to me. Like 80 speaker wire classic example. But I'm still learning so who knows. I think on my next project I'll experiment with some high end caps and see if it really makes a difference...
Yea my feelings too I use the muse caps in the signal path but who knows if they really sound any different.
 
I started working on the tone amp this morning and noticed it is a "AWG-039 C". It looks like it might be an alternate version, like the equalizer amp 'B' version that some people have (including myself). Is there any known documentation of this alternate? My schematics don't match the board...
 
I have a paper schematic that came with the original unit, which is closer to the BOM list:

Tone Amp Board (AWG-039)

BOM list || Paper schematic | PDF schematic

AWG-039: C13: 2.2uF 25v CSZA: 647-UKL1H2R2KDDANA 2.2uF 50v || 2.2/25 | 10/25
AWG-039: C14: 2.2uF 25v CSZA: 647-UKL1H2R2KDDANA 2.2uF 50v || 2.2/25 | 10/25
AWG-039: C15: 2.2uF 25v CSZA: 647-UKL1H2R2KDDANA 2.2uF 50v || 2.2/25 | 10/25
AWG-039: C16: 2.2uF 25v CSZA: 647-UKL1H2R2KDDANA 2.2uF 50v || 2.2/25 | 10/25
AWG-039: C19: 100uF 10v CEANL(NL): 647-UKL1A101KEDANA 100uF 10v || same | same
AWG-039: C20: 100uF 10v CEANL(NL): 647-UKL1A101KEDANA 100uF 10v || same | same
AWG-039: C21: 47uF 35v CEA: 667-EEU-FC1V470 47uF 35v || same | same
AWG-039: C22: 47uF 35v CEA: 667-EEU-FC1V470 47uF 35v || same | same
AWG-039: C23: 2.2uF 25v CSZA: 647-UKL1H2R2KDDANA 2.2uF 50v || same | same
AWG-039: C24: 2.2uF 25v CSZA: 647-UKL1H2R2KDDANA 2.2uF 50v || same | same
AWG-039: C25: .22uF 35v CSZA: 667-ECQ-V1H224JL2 .22uF 50v || same | same
AWG-039: C26: .22uF 35v CSZA: 667-ECQ-V1H224JL2 .22uF 50v || same | same
AWG-039: C29: 10uF 25v CSZA: 647-UKL1E100KDDANA 10uF 25v || same | same
AWG-039: C30: 10uF 25v CSZA: 647-UKL1E100KDDANA 10uF 25v || same | same

On the actual board, it looks like C13-C16 were all 2.2/50 though, which is weird. Also, there were two places where there was NO capacitor and just a little wire jumper, but I didn't have the foresight to write down which ones since I kind of ripped everything out en masse before I started. Oh well. Anyway, not sure how much it matters, just curious...
 
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