yamaha cr440 dead

[srinath]

Yamaha CR440 has no sound. Lights up and tunes fine, nothing from headphones or speakers.
Any one have a block diagram/circuit diagram schematic.
Thanks.
Cool.
srinath.

 

[Pademelon]

G'day srinath

I have a CR440 with the same problem as yours. These days I know enough about electronics to get myself into trouble. Anyway I now have it going on one channel by replacing a transistor which had its top off !!! (TR404). I also played with the protection relay which I thought had an open winding ( I might be mistaken here ). Next I will try and check the Amplifier IC on the faulty channel. I still have my original Owners Manual which has a very small scale circuit. I have attached a scan of it which is the best I can do on the forum

Regards
Pademelon

 

[prairiemystic]

Listen for the protection relay clink after you turn power on. If you don't hear it, I usually start troubleshooting there. One channel might have failed and has DC on the output so the relay stays off.
I couldn't read the schematic when I zoomed in (I can fix it in Photoshop if you have the scan) so not sure what chips it uses. Didn't see any dedicated fuses for the power amp. After seeing how cheap newer amps are, this is worth fixing.

 

[Pademelon]

Yamaha CR-440

Thanks prairiemystic,

I have one amp operating and I will try the other Amp Chip as you suggest. On reading the owners manual circuit ( with a magnifier ) the Amp is a IGO 2990 or that could be I6O 2990. I have attached a slightly better scan of a section of the circuit. The more readable scan is too large to send.

 

[east electronics]

swaping parts can often cause other problems like pcb damages

first use a procedure to troubleshoot amp arround the basics .... fuses , ofset , dead caps , soldering and so on ...

this is by far easier to do than swaping parts ....