Hi. The headphone amp is on the PRA board. Look on page 57 (pdf page, not actual document page) of the CS series servicing guide (In the files section). If you still have synth normal output then t's got to be an easy fix... maybe just a dead op amp or transistor, or maybe power isn't' getting to that part of the amp. I'd check the +15 and -15 voltages, then if they were OK, you could signal trace to check for signal maybe just before the OP2 op amp... if it vanishes on the output, desolder the old one, put in a socket and try a new one.. if it vanishes after the transistors, replace them. That would be the brain dead approach I would take. I don't think your tech would be afraid of doing that.
Keep in mind that I barely know anything about properly servicing electronics... maybe there are some other things to be careful with - like not touching live rails, but others can maybe suggest how to avoid any mishaps like that.
And I believe the PRA board comes out after loosening two screws (no desoldering of wires necessary)... I think it will be fine as long as you don't short it out against anything.
best - DT
--- In yamahacs80@yahoogroups.com, "pirimai_north" <pirimai_north@...> wrote:
>
> Has anyone had any problem with the headphone jack not working. My CS-50 has never had a working phone jack. You can use the phone jack to input into the EXT jack to create FM synthesis but I can't.
> Is this a common fault?
>
> I have the service manual but few people can fix the mass of boards and wires. My old friend was atechnician and he refused to touch my CS-50 haha
>