Tyros 4 with some audio contact issue

[fischnek]

Dear All,

I am the proud new owner of a well-preserved Tyros4.
The instrument works well in all its functions as far as I can see, with only one minor (?) fault:
Occasionally the left speaker goes silent, only the right speaker and subwoofer work. When this happens, the headphone output also only plays only the right side.
If I tap/knock the bottom left or back left side of the instrument slightly, the sound comes back and plays for a while. Then it goes away again. I have replaced the two speakers, their cables and tried the subwoofer cables, I think they are solid, there is a contact problem somewhere in the instrument.
Have someone encountered this? Do you have any suggestions for troubleshooting and solving it? I've taken apart other instruments before, soldered them, but I'm not a technician. Unfortunately there is no repair shop nearby.
Thanks for your help!
Cheers from Sopron, Hungary.

Translated with www.DeepL.com/Translator (free version)

[EileenL]

When this happens it is usually the cable from the woofer to the keyboard that is faulty. Make sure the woofer is not pushed up against a wall as this can damage cables.

[fischnek]

Dear Eileen,

thank you for your valuable suggestion. I'm afraid it's not the cable. To test this, I have completely disconnected the speaker system from the instrument. I was still experiencing the phenomenon through the headphones. Alternatively, I tried the main stereo output, where the same thing happened. The left side sometimes goes silent, then sounds again when struck.
Any other suggestions?

thanks
fis

[overover]

Hi fis,

Welcome to the PSR Tutorial Forum!

I suspect the reason for the problem (intermittent loss of the left channel) is an internal cable / connector connecting the master volume dial to the main board, or it's the master volume dial itself. I'll get into more detail later.


Best regards,
Chris

[overover]

Hi fis,

Here are the promised details on your problem with the Left channel dropping out through the main outs, headphone output and subwoofer output (which feeds the left satellite speaker):

On the Tyros4, the (stereo) master volume potentiometer directly controls the analog Left and Right master signal coming from the DAC (digital/analog converter) IC951.

Behind the master volume potentiometer, the signal goes via separate OP amps to the outputs Line Out Main, Phones and the 8-pin socket for the subwoofer.

So I think the error in the analog signal path is between the Left output of DAC IC951, Transistor FT300, IC300, Master Volume potentiometer VR302 and the connection cable/connector on the AJACK board. See also the Block Diagram in the Tyros4 Service Manual, page 161.

You can download the Service Manual here if you need it:
>>> https://psrtutorial.com/lessons/workshops/ServiceManuals.html


First, I recommend turning the master volume dial all the way up and down very often. Possibly "only" the Left potentiometer track is slightly damaged and the problem improves as a result.

If this doesn't help, you'll probably have to unscrew the Tyros4 to track down the problem. (If you don't have the appropriate electronics experience, you should leave the troubleshooting to a technician).


P.S.
You could test the signal at the AUX OUT sockets. If I am correct in my assumption about the error, the Left channel should NOT fail there, since the AUX OUT signal is not controlled via the master volume dial.


Hope this helps!

Best regards,
Chris

[fischnek]

Dear Chris,

thank you very much for your help.
I tried it right away, and you are right, the sound on the AUX OUT output is OK, on both sides, under all conditions.
Regarding the master volume dial, I think it is not related to the issue. If the left side sounds fine, no matter how I turn the volume, the left side sounds fine. If it doesn't, no matter how I turn (how often, how fast etc) the volume, it still doesn't sound. So it's not the "usual" potentiometer problem.
The volume knob has no effect on the problem, but tapping the lower left - left rear of the body of the instrument will trigger the fault or solve it. Somewhere below or behind the "Mic" and "Song" buttons - area.
What are the chances of finding some faulty cable soldering there? Or is it on all PCBs?

[overover]

Dear Chris,

thank you very much for your help.
I tried it right away, and you are right, the sound on the AUX OUT output is OK, on both sides, under all conditions.
Regarding the master volume dial, I think it is not related to the issue. If the left side sounds fine, no matter how I turn the volume, the left side sounds fine. If it doesn't, no matter how I turn (how often, how fast etc) the volume, it still doesn't sound. So it's not the "usual" potentiometer problem.
The volume knob has no effect on the problem, but tapping the lower left - left rear of the body of the instrument will trigger the fault or solve it. Somewhere below or behind the "Mic" and "Song" buttons - area.
What are the chances of finding some faulty cable soldering there? Or is it on all PCBs?

Hi fis,

I rate the chances of finding and fixing the fault as relatively high.

If I were you, I would unscrew the Tyros4 and first check whether the wide connector on the MICVR board (on which the master volume control and the mic gain control are located) has good electrical contact (e.g. pull it out and plug it back in several times).

Then trace the route of the white cable bundles from the MICVR board to the AJACK board (where the Line Out jacks are) and check the cable connectors there as well. (See the two attached pictures.)

Cables also go from the AJACK board to the DM board (mainboard). If you haven't had any success yet, I would also check these connectors on the DM board. (The sheet metal cover would have to be removed for this.)

But before that, please make sure to watch the following YT video. This also shows how to open the T4.
>>> https://www.youtube.com/watch?v=iaxE4i9x_S4

I suspect it's the mentioned connector on the MICVR board, especially since you wrote that the fault responds to "tapping the lower left - left rear".

Very important: Before you touch electronic components / boards inside the T4, you should definitely (just before) discharge your body by touching a grounded metal part with both hands (e.g. bare part of the central heating or water tap). Then, if possible, do not walk on carpeted floor so you don't get static electricity again.


I hope you can fix the issue!

Best regards,
Chris

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[fischnek]

Thank you so much for your help. I will try this later during the week, and let you know the result. Anyway, it is my pleasure to be a part of this community, and to have your assisstance in my problem. Thanks!!!

[overover]

You're welcome, fis, thanks for your kind words!


Best regards,
Chris

[fischnek]

Hello,
It took me until I felt brave enough to open the instrument.
I did. ... so much dirt in one place!!! :-( I have to clean it up.
Anyway, following overover's advice, I quickly found the fault, one of the connectors had come loose, I simply had to reconnect it. (see picture)

... in the meantime i noticed that the registration memory button 2 is not working, but i might check that now.

thanks again for the help, now I can really enjoy the instrument.

Take care of yourself and help others, the appreciation will surely not be missed.

cheers

fis

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[Divemaster]

Well done to you for having the courage to open the case and check out the Tyros.

Not the easiest of jobs, but you found the problem !

Have a lot of enjoyment with your new Tyros 4.

[Toril S]

Well done!