power supply capacitors for Sony STR-AV920 receiver

I was asked to fix the hum problem of this 20 years old Sony receiver. I download the service manual and plan on trying to replace the power supply capacitors first (Sony Parts no. 1-125-479-11). The C801/851 capacitor are 10000uF/63V electrolytic with very unusual terminal pattern. Anyone knows what they are and where to get them?
IMG_1186.jpg
 
Are they low esr?
No point in replacing the main smoothing capacitors if they are not faulty. I have had 40year old Sony capacitors that read good without issues and traced the fault further down the line, usually poor ground connections.
They are made specifically for Sony by their capacitor company in Japan, probably Rubycon and are extremely reliable.
You will find, if 100/120HZ hum one of these has gone dry;
 

Attachments

  • Screenshot 2020-01-03 at 09.30.06.png
    Screenshot 2020-01-03 at 09.30.06.png
    95.1 KB · Views: 47
Last edited:
Are they low esr?
No point in replacing the main smoothing capacitors if they are not faulty. I have had 40year old Sony capacitors that read good without issues and traced the fault further down the line, usually poor ground connections.
They are made specifically for Sony by their capacitor company in Japan, probably Rubycon and are extremely reliable.
You will find, if 100/120HZ hum one of these has gone dry;
Thank you for your suggestion which is very helpful. Can you explain what do you mean by "one of these has gone dry"? What are the devices you refer to? What do you mean by "gone dry"? Do you mean the connection to and from the POWER IC BOARD?

If I poke around the schematic part you showed for 120Hz hum with a scope, what do I look for and where?
 
Last edited:
If the insides of a filter cap dry out chemically, the cap can lose function. In that case you would get hum in your signal.

But please don't guess and throw parts at it. I agree, scope or otherwise measure the ripple on those power supplies. Let's find out if the caps are the issue. COnsider that the low voltage supplies for the preamp could just as easily be at fault. A grounding issue could be involved.

120Hz hum comes from power supply ripple. 60Hz hum comes from grounding or other things.

Hum is not generic, there are a hundred potential sources of hum, and each has its own cure. Adding filter caps will do nothing for ground trouble. And vice versa.