Yamaha DX7II missing right channel

Anyone know what might cause the right channel to stop working? I replaced the volume slider with a new one. Should I start by testing the headphone jack and work backwards?

that sounds like a good idea. in the DX7 MK1 the audio channels are basically the same on all outputs. so if the right channel does work on the headphones, you know what to look for.

Thank you for the reply. I should have been more clear about the problem. This is a synth I bought as-is, which needed various repairs. I haven’t tried the audio out jacks yet, just the headphone jack. (I don’t have an amp, so if someone can suggest a way to test the output jacks, I’d appreciate it.) As for the headphone jack, here’s what’s happening: with the plug inserted all the way, only the left channel works. If you pull the plug out about halfway, both channels will work.
I desoldered the jack, sprayed it with Deoxit, and tested the three pins for continuity, and it appears fine. My plan is to replace it anyway and see if that fixes it. If it doesn’t, what’s the next thing to look for?

Thank you.

from what you tell me there could be a problem with the headphone amp or something on the soundboard, it would really be a good idea to test those outputs, because the DX7II has stereo outputs. I have a schematic here for a DX7 MK1 but it will be different for your synth.

for testing purpose you could use a jack to Cinch/RCA and try it on a hifi-set