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Pioneer SX-3700 upgrade to 15000uF caps?!

jpreza

jpreza

Active Member
Happy Monday everyone,

I'm in the middle of recapping a Pioneer SX-3700 receiver. After looking at options regarding the current 8200uF caps, I've read that other AKers have upgraded to 10000uF. I'd like to take it further and use 15000uF high quality caps from either Nichicon or Samwha which are the same diameter as the original.

My question is: are there other things to consider before in essence doubling the capacitance? Should I upgrade other caps beside these two?

TIA....JP
 
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I'm not sure but you might run into excessive inrush current when you first turn it on. Some receivers with caps that big have a soft start circuit to mitigate that.
 
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The old caps likely measure at or close to 10 if you were to do a capacitance test. 10k is rational, will give you a bit smoother low end. Raising uF supports bass, dropping it supports highs. Just beware that as you raise capacitance you are dropping the voltage to your main rails.... which means you are working the power supply harder. In my experience there isn't much to gain from jacking up filter uF, more about getting some the unit will jive with
 
12344321 said:
The old caps likely measure at or close to 10 if you were to do a capacitance test. 10k is rational, will give you a bit smoother low end. Raising uF supports bass, dropping it supports highs. Just beware that as you raise capacitance you are dropping the voltage to your main rails.... which means you are working the power supply harder. In my experience there isn't much to gain from jacking up filter uF, more about getting some the unit will jive with
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The original 8200uF caps are reading close to 5800uF which I guess it's pretty good for 40+ years of service.
 
I would say that the guys who designed that unit probably knew what they were doing, and going over about 10K uF won't really gain you anything other than an overworked transformer and bridge rectifier. Not only power on inrush current, but any time the charge on the caps is depleted, it has to be recharged.
 
Bigger caps won't change the voltage that results in clipping since that's determined by the rail voltage. Up to that point you may get better low frequency response, but remember that drum beats are NOT low frequency clean waves, they are a complex waveform riding on a single rise followed by decaying harmonics. One of the fun subjects in physics class was vibration modes in diaphragms. They do all sorts of crazy things at variable frequencies depending on weight, size, tension, and impact. Bigger caps have little impact on those higher frequencies.

It was fun to see the "distortion" from undersized caps in that video -- what was causing the "distortion" was the 120 Hz recharge of the caps. Larger caps let the PS "fly over" that because there was sufficient current available to prevent voltage disruptions. And 1000uF for a 30 watt/channel amp is insane, my Heathkit Compact had 1000uF for 10 watts per channel! My Technics turntables have 1000uF 35V main filter caps, and all they do is turn the platter and move the tonearm.
 
Curious if there's anyone that can offer advice here. I see a lot of threads discussing replacement filter cap sizes, but it's mostly theoretical & not much of iron clad/tried & true advice - unless I'm missing something. I have an SX-3700 with bad filter caps and power transistors 2SC2525 x2 & 2SA1075 x2. Question is two-part: does anyone have a capacitor that they have good experience with/that they've personally used? All due respect, not looking for a user to take the specs and do a Mouser search and report back/want to hear from people with experience as I can surmise on my own. Secondly, would mouser #647-LLS1J103MELB work as an upgrade to the factory 8,200uF/50v the unit comes with? Thanks in advance!
 
I think that replacement part # will work fine. It's a 10,000uF and I'd expect it to measure more like 9,000uF since all the manufacturers seem to intentionally target the low side of the tolerances these days. If you go up much farther though you'll probably have to think about a soft start circuit. I haven't looked at a 3700 schematic but guessing there's no soft start in that model already.
 
Brian1970 said:
I think that replacement part # will work fine. It's a 10,000uF and I'd expect it to measure more like 9,000uF since all the manufacturers seem to intentionally target the low side of the tolerances these days. If you go up much farther though you'll probably have to think about a soft start circuit. I haven't looked at a 3700 schematic but guessing there's no soft start in that model already.
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Totally. Yeah I've never worked on this specific unit but I've done this upgrade on similar spec filter caps/no soft start with no issues & seems plenty of other users have as well. Should be fine. Hard to find a step up with these specs that have dimensions that will work on this board. Anyway, thanks for the confirmation. There's so much conjecture on AK when it comes to these filter caps on an SX-3700, so thought I may be missing something when I quickly found this on mouser but noticed no other posts/past projects using this one..
 
8200 uF caps may be easier to find anyway. I'd go up a voltage rating, line voltage is a little higher than it was when that unit was new, and sometimes manufacturers ran them very close to voltage limits.

Higher than 10,000 uF would just be wasting your money, 8200 uF is plenty for 45w/c. Personally, I've never run any amp close enough to output rating to stress the main filter caps, a couple watts is more sound pressure than I want anyway.

If you have shorted output transistors, everything from the differential pairs on is suspect, and very likely at least one of the main filter caps has been over-stressed. Only times I've found bad main filter caps is when an output was blown. Shorted outputs is also short circuited main filter caps, and a direct short on a fully charged 8200 uF cap can generate some heat!
 
painttoad said:
it's only 45wpc. i can't see any benefit to using a pair of 15,000uf caps.
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Wait are you responding to my question about the 647-LLS1J103MELB (mouser) being ok to use, or the posts about using 15kuF from 2023? Agree 15kuf would be overkill on this application - was asking about the mouser number mentioned here which is 10kuf/62v I believe. Thanks!
 
AndyCares said:
Wait are you responding to my question about the 647-LLS1J103MELB (mouser) being ok to use, or the posts about using 15kuF from 2023? Agree 15kuf would be overkill on this application - was asking about the mouser number mentioned here which is 10kuf/62v I believe. Thanks!
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ahhh, i see...this is what happens when you piggyback someone's thread.
 
painttoad said:
ahhh, i see...this is what happens when you piggyback someone's thread.
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Oh I apologize; didn't know piggybacking was an issue as long as the post was inline with the overall subject. On the other hand, I see other users giving grief to users that start new threads when there are existing ones on the subject. Seems I have a lot to learn about forum-posting etiquette! Duly noted/thanks for the heads up..
 
AndyCares said:
Oh I apologize; didn't know piggybacking was an issue as long as the post was inline with the overall subject. On the other hand, I see other users giving grief to users that start new threads when there are existing ones on the subject. Seems I have a lot to learn about forum-posting etiquette! Duly noted/thanks for the heads up..
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When I have an issue I can't figure out I'll search the forums for similar threads. This usually gets me what I need.

I don't piggyback an old thread unless it's helpful to the original. I think I did that one time regarding the repair of a sub where I added more information to help with the repair.

If you can't find something, start a thread. Don't worry about what others think. You're looking for help and they should provide some or leave well enough alone.
 
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