Pioneer SX-525 problems...
- Thread starter mattsd
- Start date
I also edited MY posts above... but yes.
A little less than 100 ohms if possible (82?), since it may already be starting to turn on at 100.
But if it makes getting two resistors harder, just go with the 100's.
IF you are going to order out for the resistors, please consider getting the KSB/D's.
But if it makes getting two resistors harder, just go with the 100's.
IF you are going to order out for the resistors, please consider getting the KSB/D's.
mattsd
Super Member
Okay, I think we are doing good!
I could only find one 100 ohm (darn!) but with in the right channel I was able to set the idle current to 30mv solid. The transistors got warm at this level so set down to 20mv and it seems to be fine. The pot is at about 70-75 ohms I would estimate.
I could only find one 100 ohm (darn!) but with in the right channel I was able to set the idle current to 30mv solid. The transistors got warm at this level so set down to 20mv and it seems to be fine. The pot is at about 70-75 ohms I would estimate.
mattsd
Super Member
Mark, should I order the transistors? Or do I need to do something else? I just let it play for about a half hour on both channels (found another resistor!) with the idle current set at 25mv and it worked just fine at low volume, transistors stayed warm, but not hot, however, when I turned up to about 1 watt power output with the treble knob at full right, it started clipping lightly. The bass was at flat. But if the treble knob was at flat, then it was fine at that output.
Just winging it here, but those are original caps? If so, any attempts about profiling frequency response really can't be trusted as typical performance.
mattsd
Super Member
No, the only caps that are original are the 3300uF filtering cap and the two 2200uF coupling caps. I did a complete recap of the control amp and the head amp, the control amp definitely needed it as it would send 3-4v DC pulses through the main amp every time you turned the bass knob, which is probably why the outputs and other components failed. I found this out when I had the voltmeter connected to the speaker terminals and I turned the bass knob. This was before I put in the new components, by the way.
I owned another 525 that did the same thing, unfortunately that was before I found all the wonderful and helpful people here, and before I started the hobby of repairing these vintage receivers, so I took it apart! :thumbsdn:
Oh well, I did have the presence of mind to save the parts from it, knobs, lights, etc. So to all you people out there with a SX-525, I would highly recommend that you recap the control amp. The difference it has made with mine is astounding and you will probably save yourself a lot of headache down the road.
Mark, just FYI, the caps I replaced the control and head amp with are the same kind that you had me replace the main amp with, the Nichicon low impedance, 105C caps.
edit: should I replace the main caps? I honestly think that the coupling caps are leaking. I connected a junk speaker after I had turned it on and as soon as I connected the negative wire and touched the positive wire to the positive terminal, the speaker popped quite loudly. I removed the wire and then tried again and it did not pop. What would you recommend?
I owned another 525 that did the same thing, unfortunately that was before I found all the wonderful and helpful people here, and before I started the hobby of repairing these vintage receivers, so I took it apart! :thumbsdn:
Oh well, I did have the presence of mind to save the parts from it, knobs, lights, etc. So to all you people out there with a SX-525, I would highly recommend that you recap the control amp. The difference it has made with mine is astounding and you will probably save yourself a lot of headache down the road.
Mark, just FYI, the caps I replaced the control and head amp with are the same kind that you had me replace the main amp with, the Nichicon low impedance, 105C caps.
edit: should I replace the main caps? I honestly think that the coupling caps are leaking. I connected a junk speaker after I had turned it on and as soon as I connected the negative wire and touched the positive wire to the positive terminal, the speaker popped quite loudly. I removed the wire and then tried again and it did not pop. What would you recommend?
Last edited:
OK, new electrolytics. Control amp, head amp and power amp.
This does this treble thing on both channels? Plus I can't call it clipping for sure without a scope - I will say it can sound like clipping and is distortion.
You MUST be sure it is on both channels equally, otherwise it could just be something like a treble pot needing cleaning.
In the absence of my usual instruments, I would do a bit of a balancing act, turning up the volume and fiddling with the treble to find the point where the distortion kicks in and whether that point moved down the treble dial as the volume dial is kicked up.
Clipping will probably track on the two dials somewhat, but distortion in the control amp will be more related to the treble adjustment regardless of the volume setting.
As to what to do, without instruments.... not a lot... hope it's cleaning, and one channel.
mattsd
Super Member
Okay, it is not clipping! :thmbsp: It was my CD player! I went through a bunch of CD's and found it would do the same "clipping" thing when it got to a dirty spot in a CD. I have it playing next to me right now and it sounds fantastic! I had both controls at flat then at full and then back to flat while adjusting the volume and it was fine. I did find that the volume pot is little dirty, as the THD would increase as I turned it up with no input, then decrease as it went past a certain spot, so it is getting cleaned. Other then that, it's working fine.
However, I still am questioning the filtering caps.
However, I still am questioning the filtering caps.
Probably won't make (much of?) a difference, but I won't get in the way...
The newer caps are going to be smaller, making innovation necessary to mount them. You can go up in capacitance and voltage for larger caps to fit (to a reasonable degree, may have to put in modern rectifiers to handle the turn on surge)
Go with nichicon UPW caps, then UHE, then Panasonic FC or FM.
Bypass the power cap with 1uf stacked film (ecq) caps. That WILL make a bit of a difference.
You can try doing the same on the 2200's but we will have to watch the amp for stability and evaluate the change in sound independent of the power cap's (3300) bypassing,
Last edited:
mattsd
Super Member
Just to confirm, bypassing the power cap means soldering the film cap across the terminals of the power cap, correct?
As for the main caps, I could not find the ones you suggested in the size diameter on Mouser or Digi-Key, even though I went up about 20% in size from the originals, however I did find these:
3300uF: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P7510-ND
2200uF: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P6675-ND
As for film caps, what do you recommend? Polyethylene, plastic or polyester?
As for the main caps, I could not find the ones you suggested in the size diameter on Mouser or Digi-Key, even though I went up about 20% in size from the originals, however I did find these:
3300uF: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P7510-ND
2200uF: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P6675-ND
As for film caps, what do you recommend? Polyethylene, plastic or polyester?
yes: soldering the film cap across the terminals of the power cap
use Panasonic ECQ caps. Look up their specs for details.
Hard to say on the big caps - mainly mounting considerations.
I have mounted ( in the formerly clamped caps places) caps soldered into a small oblong pcb that had holes that matched holes in the chassis, and most of the foil removed to avoid shorts.
mattsd
Super Member
This film cap?
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P4548-ND
I had never thought of that, in fact that gives me an idea on how to mount the caps.
Thanks a whole bunch for all that you have done for me, Mark, I really appreciate it. Next time I get a 525 that does this, I'll know what to do! :yes:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=P4548-ND
I had never thought of that, in fact that gives me an idea on how to mount the caps.
Thanks a whole bunch for all that you have done for me, Mark, I really appreciate it. Next time I get a 525 that does this, I'll know what to do! :yes:
I should have said: use THAT ONE.... for a few pennies more, as well as that they have more in stock too iiac...
mattsd
Super Member
Well, I finally received and replaced the main caps and put the bypass cap across the terminals of the power cap and wow! Even better then before, and I thought that was good! I have had it playing for a while to break in the new caps and it keeps getting better and better.
Thank you, thank you, Mark for all you have done, you ARE the man.
Thank you, thank you, Mark for all you have done, you ARE the man.