Pioneer SX-525 problems...

[markthefixer]

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.

Once the amp and your ears have settled in together, try putting similar caps across the two big output capacitors, and see how that does... Sometimes it's good, sometimes it isn't...

 

[mattsd]

I will do that, I'm up to my ears in the SX-636 right now, but if I find time, I will do that. Thanks!

 

[TomHarrison1]

Ok, that is progress.

Either we add resistance (another 47 to 100 ohms fixed resistance) or change the outputs to the KSB/D transistors I mentioned.

My numbers are old... let me check...

I grabbed those old numbers from an old post, these are the in-stock numbers that I maintain in my master list.......
(da%$ shortcut bit me in the A!! again)
512-KSB596Y pnp to-220 bce 80v 4a 30w 3mhz 15-240hfe $0.62
512-KSD526Y npn to-220 bce 80v 4a 30w 3mhz 15-240hfe $0.62

I know this is an old thread, but I just want to mention that with the 525 I recently worked on, I tried using the TIP outputs and could not get bias down to 30 mV (lowest I could get to was about 70 mV). With the KSB596 and KSD526 pairs, both channels dialed in easily at 30 mV.

 

[markthefixer]

Onsemi seems to be migrating all of it's transistors to the "new whatever" that slightly lowers the Vbe.
Eventually this approach will have to be tried & perfected:
Increasing R26 from 4.7k to ??? (check e24(5%) resistor values series) to reduce the current through the thermal diodes and thus the voltage decreases.

Right now it is unknown how much of a current drop is needed per millivolt etc for the thermal diode...

I HATE to do mods, but this is becoming unavoidable.