Is something broken? Can't tell with the info given

The outputs of the MOXF are unbalanced.
Please use standard Tip-Sleeve (TS) cables when connecting the MOXF to your sound system.
Never plug the headphones into anything but the "Phones" jack. It has a TRS (Tip-Ring-Sleeve) connector and would give meaningless results plugged into either the "L/Mono" or "Right" jacks.

The "L/Mono" jack (use only a standard TS signal cable) when used alone, phase coherently sums the Left and Right channel signals. It is to be used alone only when you cannot connect your instrument to a true stereo system.

Plugging a single (TS) cable to the Right side will only deliver the Right channel items.
As soon as a TS cable is plugged into the Right Out, signal is automatically divided in true stereo... Left to Left, Right to Right.
Therefore one cable to the "L/Mono" will certainly sound louder, fuller than one cable to just the "Right" output, that is normal. After all both channels are routed to "L/Mono" alone, and only Right signal is delivered to "Right" alone

Use the correct cables.
And never use TRS jacks in the outputs.
Headphones should only be connected to the Phones jack.
(And need I say, never connect a TS cable to the Phones jack)?

With this information, redo your tests.
Yes, the type of cables matter... and never plug your headphones in the Main Outputs!

Thanks Bad...
Yes, standard TS signal cable always.
IF TS inserted into L/Mono (Right empty) = Signal good (although I think it's the Right Channel only with no left)
IF TS inserted into Right (L/Mono empty) = Signal good
IF TS inserted into L/Mono and second TS inserted into Right = No Left channel signal at L/Mono jack. ONLY Right channel signal at Right jack.

I'm guessing the Left channel is not appearing at L/Mono. When a TS cable is plugged into L/Mono and Right is empty what I am hearing is the Right channel (summed into the L/Mono) jack. When I plug a second TS cable into Right jack I hear the Right Channel on the Right jack. The L/Mono has no signal as the Left channel is messed up.

Could it be the Left channel Opamp is messed up? That would explain why the left channel signal in the phones jack (with TRS cable) is faint and distorted compared to a strong Right channel signal.

Okay I understand what you wrote, try bypassing the Effects and instead of guessing, actually Pan a signal in your experiments. This will allow you to be sure if the signal is reaching the tested output or not

But it very much sounds like you have a bad component somewhere.
If you determine that is the case, you should contact an authorized service location.
If you need help in finding a service center let us know. Sorry you are having this issue, let us know.

Thank you for the responses!- I ran the diagnostic tests and encountered the same results. The Left output test presented no sound at all at the left jack. The Right output test presented sound at the right jack. Something must be wrong - bummer.

Perhaps I'll have them fix the broken black keys - surprised how quickly they have broken. The F#s seem to break very quickly (broken two F# in two years) too many glissandos I suppose.

Hi Marc, I'm having exactly the same problem. Did you find any solutions? Thanks

If you determine that is the case, you should contact an authorized service location.

MOXF 8 V1.12 firmware. Need Help!! Please! L/Mono output is active when ONLY L/Mono is being used.
L/Mono is 'dead' when Right Output is being used.
Right Output works by itself or when both L/Mono and Right are used.

L/Mono => Sound
L/Mono + Right => No sound at L/Mono, Sound at Right
Right => Sound

Headphones: Left = very faint sound (regardless if right is plugged in) Right = loud and clear.

Is something broken? I take such good care of this keyboard - can't believe there is a physical issue/defect. Appreciate any help provided.

Marc, if this is anything like the problem I've discovered (and fixed several times) on my MOXF6, it sounds like you have a loose audio jumper connection between circuit boards. The first time I encoutered the same issue with one side of the stereo outputs AND headphone out being dead or distorted, I took it into an authorized repair shop. They charged me about $100 to "fix" it, which involved opening it up and discovering a jumper had come partially unplugged. That "fix" lasted for about a month.

So, being a person who likes to fix my own things, since often I will do a better job than some repair shops, I opened it up, found a very obviously loose two-lug connector, and voila, all back to normal.

My theory is that normal moving around of the keyboard, even in a protective case, is enough to jar it loose over time. The third time it happened, I decided to add some good tape to hold the plug in place. I haven't had any problems since then.

Hope this helps. It's worth a peek inside, if you're a careful investigator type.

PK

I am having the exact same problem - could not see any loose cables or jumpers

I have the same problem on my MOXF6. L/Mono has no sound (or very faint) while R output is fine. I'm way in the sticks, so no authorized service center for me. I tried to find a "two-lug connector" mentioned by Phil but no can find.

Anyone else find a loose jumper or connector that may be the culprit and approximately where I might find that? I'm assuming I need to be looking on the beige board on which the output and other jacks are attached.

Interestingly, my name is same as the original poster (Marc with a "c"), just to add to the confusion 😉

I'm having the same trouble, hoping to revive an old thread.

I've opened the keyboard up and currently don't see a loose jumper/connector. Any advice to as to where to look? I'd like to unscrew as little as possible.

Thanks.
-Greg

Any advice …

you should contact an authorized service location.

However, you did not state your problem… the Left jack alone always sounds different from the Right jack alone.

Left jack alone will phase coherently merge the Left and Right Channels. You can see it is labeled “L/Mono”.

The Right jack alone only outputs the Right Channel of the Stereo mix.

Both cables output Left channel to Left Out, Right channel to Right Out.