Yamaha CR-820 receiver issue

[cancon]

Hey DIYers',

I've got a CR-820 which has a problem upon cold start-up - after the protection relay engages, the first 5 seconds of using the volume knob produces loud static noises. I need to wait a while to reproduce the issue, hence cold start-up only.

I have a feeling it's a capacitor - DC voltage on the pot would explain the noise, cap charge and discharge time would explain why the problem fades and then doesn't return until the amp is cold again.

Am I on the right track? Any tips on where to starting looking would be appreciated!

http://akdatabase.org/AKview/albums/userpics/10007/Yamaha CR-820 Service Manual.pdf

 

[rayma]

Yes, this is either a dirty pot or a leaky capacitor near it. If the problem goes away with warm-up,
it's more likely to be a leaky capacitor. First clean the pots with deoxit D5.
https://www.amazon.com/Hosa-D5S-6-DeoxIT-Contact-Cleaner/dp/B00006LVEU/ref=asc_df_B00006LVEU/

Capacitors that could be leaky: (The values are hard to read)
C650/C657 (2.2uF)
C709/C710 (4.7uF)

 

[chrisng]

this is either a dirty pot or a leaky capacitor near it. If the problem goes away with warm-up,
it's more likely to be a leaky capacitor. First clean the pots with deoxit D5.

+1, also check C601/C602 could be the culprit.

Is the noise happening on all inputs or just the tuner?

 

[rayma]

Yes, in fact those capacitors are the most likely ones to replace,
if it is the volume knob rather than the loudness control that makes the noise.

 

[cancon]

Thanks for the input!
Noise happens regardless of input selector position, and always on the volume control only.
I will report back, it may be a while though.

 

[rayma]

Ok, watch out for the capacitor polarity.

 

[chrisng]

My suggestion is to use through hole film capacitors if space allows, or use SMD film capacitors solder to the copper traces.