troubleshooting a Yamaha CR-1000

[cjkpkg]

Hello,

A buddy of mine asked me to look into an intermittent issue with his CR-1000.

Occasionally and more frequently lately the amp would cut out/distort/snap/crackle and then go into limp mode.

I was able to do this with a DMM on the speaker terminals looking into the DC. One channel was hovering nicely at about 5MVDC. The other channel was hovering at about 110MVDC. I had the "event" happen luckily as I was watching the DMM. It shot up to about 1100MVDC as the crackling was happening - then it went in to limp mode as usual. Not sure which happened first...the rise in DC or the crackle but surely related.

I have observed this happen regardless of the input AUX TUNER were the two I personally observed it happen.

So, I guess my question is where can I look to the cause of the DC surge on the output? Is 110MVDC enough to kick in the protection circuit?

LINK TO SM
someone over at AK was nice enough to post a link to the SM...

here is a shot of the protection circuit and the main amp circuit

[sakis]

replace all electrolytics .... all means all .....unless this unit was stored in a refrigerator

if not then all capacitors are leacky

then make sure that offset adjustment trimmer are clean and functionabe ...of course better to replace with multi turn

make sure that TR 602-603 have no soldering issues ....

there is a chance that your amplifier will play without changing all the electrolytics ... all means all ....but replacing them will guaranty that the unit will play properly for another 30years

regards sakis