Headphone out on JVC reciever only half-working, need help

[danny_d]

Hey guys!
I have an AV Receiver (JVC RX-5022V) which started to have a really annoying problem recently, which I hope you could help me with.
So basically, the issue is that the headphone output only works on the right side channel (and doesn't output anything to the left!)
This is the only problem it's having (everything else appears to be working fine). And just to be clear, this only occurs in headphones mode (in speakers mode, the balance is perfectly fine, but in headphones mode, only right side output, which is really annoying since I use my headphones quite often!) Also, I've had my headphones tested on multiple other devices and they're fine, so it's definitely not that. And it's not an issue with the source either (tried PC/DVD/Radio all produce the same result). I've tried opening it and checking the headphone jack with my multimeter (used a 6.3MM>3.5MM adapter along with a dual 3.5MM>3.5MM male cable, had it plugged in, tested with continuity the right/left/ground from the legs of the headphones jack to the other end of the 3.5MM jack, everything turned out fine there, and no shorts in-between) other than that, I'm a bit at lost of how to proceed!). You can find the service manual for it here:
https://elektrotanya.com/jvc_rx-5020vbk_5022vsl.pdf/download.html
Please advise me what to do next, thank you!

[Bushougoma]

The headphone connector contacts are good (no pitting or heavy oxidation and they mate to the headphone plug solidly) and there are no cracked solder joints mounting the jack to it's PCB? They may not be obvious at first glance you may need magnification. Inserting and removing headphones often causes these joints to crack. If not it's time to dive into the schematic.

Look at page 28 bottom left I believe J1331 is the headphone output. It looks to be mounted on it's own PCB and is connected with some type of connector remove and reseat the connector also reseat connector FW341. There may be oxidation on the contacts causing a poor connection.

With the headphone jack PCB disconnected check the 330P C1332 capacitor on the left channel make sure it's not shorted and check the 470 ohm R1331 series resistor make sure it's not open.

At this point I would start signal tracing by inputting an audio signal and probing the audio path with a scope to see where the left channel is dropping out.

Connect a scope between pins 1 and 2 of FW251 with the headphone PCB still disconnected. Is the left channel present?

If so the issue is on the headphone PCB.

If not check at the input of relay RY203 via pin 1 of FW341 is the left channel present?

If so check the solder joints on RY203 for cracks if the joints are good the relay contacts for the left channel in RY203 are bad. Since one channel is working power to the coil is present and the transistor ground side switching the coil is fine.

From there it simply taps into the left speaker output which is working so you should find your signal at FW341.

[IanMacdonald]

If the socket contacts are OK, a dry joint on its PCB is the likely culprit. Vibration eventually takes its toll here.

[danny_d]

Thanks for your help guys, it's much appreciated! 
Back to it, I don't see any bad solder joints (and I also tried to resolder the headphone jack with no change)
The headphone jack is soldered into a very small PCB (which has two resistors, R1331 and R1332, and two special, resistor-shaped capacitors, named C1331 & C1332) and is then connected to a larger circuit board via a 3-conductor flat cable (FW251), which is soldered on both ends (tried to resolder that one too, but again, didn't make a difference). Apart from that, both R1331 & R1332 are fine and shows 470 OHM on my meter.
C1331 & C1332 seem to be okay also (desoldered and checked capacitance, both were on the same level).
FW341 (in similar to FW251) is also a flat multi-conductor cable (except that it has 5 conductors instead of 3) which connects it to another circuit board which does all the processing and has the two main, big capacitors. Haven't tried resoldering that one yet, maybe will do that too soon.
There's also a transistor (A1046) on the beginning of that 3rd circuit board (right next to the FW341 cable), I'll have it tested later, maybe it's somehow related. As for the relay (RY203) I'm not sure how to test it (as I haven't tested any before) so some guidance would be great!
Apart from that, I only have a multimeter (UT139C), a capacitance+esr meter (ESR70) and a soldering station (FX888), so no scope, please keep this in mind. Also, not sure if it matters, but I've noticed that if I turn the volume really high, there is very (slightly audible) output from the left side, so it's not completely muted.

[danny_d]

Just to update you guys, I figured it out!
R203/R208/R210 are all fried (open circuit), and D220 also conducts both ways (so is also fried)
I don't really have a stockpile of components, so it might take me a while to obtain em (and may have to order em online)
I'll post here again once I have the results. Hope things would go well after I replace these components 

[Bushougoma]

All of the resistors mentioned are fusible resistors they wouldn't go open circuit unless there was an abnormal amount of current flowing through them.

Check the bridge rectifier diodes supplying the unregulated 23 volts DC D201, D202, D203, and D204 make sure none of them are shorted or open.

Also check the unregulated 14 volt rectifier diodes D206, D207, D208, and D209.

Check the pass transistors (Q205 and Q203) and all of the zener regulator components surrounding them.

[danny_d]

Just to update you guys, the bad components have been replaced, and all is well now! 
And yes, turns out Q203 had issues also, so I've had it replaced too.