Yamaha CLP-300 problem

Hi fellas.
I have an old CLP-300 I am trying to repair for my niece. I replaced the main board and it works pretty well however there is no sound out of the right speakers nor the right side of the headphones. There is however a faint hissing/popping, which tells me that everything after the Power Amp is in order. Any one got any ideas? I’ve cleaned the volume pot.

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Add signal into AUX IN and see if both channels work - then you know if pot is OK

Brilliant! I don’t know why I didn’t think to do that. I did just that and got sound through so as I see it it can only be the pot, or whatever those mix and invert blocks indicate.

Short the pot out - two wires soldered between input and swiper

That inverter just makes an artificial stereo signal - so it’s IC26, or IC27 or volume pot or contacts/wiring between main board and volume pot or corroded circuit board track (seen many of them)

I forgot to update this. I solved this issue and it was indeed the volume pot. I suppose the wiper from the right side broke or else the carbon trace had a fissure in it. Shorting across the pot gap me full volume. I replaced it and now my niece has a rather nice piano to learn on. Thank you very much, wernersaurus. By the way where did you get the above schematic? I purchased the service manual online and it does not have such a schematic, only a block diagram.

I am a YAMAHA, CASIO, KAWAI, ROLAND and KORG Service Center - so got internal access

Thank you for this useful thread, which has helped me diagnose a similar problem with a CLP-820S. In my case as well, it appears to be the volume slider which has failed, causing the right speaker and headphone channel to be silent with either built-in synthesis or aux input, whereas aux output works fine since it bypasses the volume control. Soaking the linear pot with contact cleaner (I have reason to believe that the previous owner let it get moisture in it) and jiggling the slider a bit causes the missing right channel to heal temporarily. This seems like it’s time to order a replacement linear pot, but I don’t see it on the CLP-820 page of your website. Do you have one available listed elsewhere maybe?

Edit: I see part #3696 on the page for the contemporaneous CLP-840. Is my instinct correct that that will be appropriate here?

Follow up: I didn’t get a reply, but I ordered the part anyway. It arrived very quickly, and installing it was simple and successful. This old Clavinova is now good as new!