Hi everyone,

First I would like to thank the people helping to solve the problems encountered here, I already red lots of really helping posts and wanted to show my gratitude.

I ask your help today to repair the old S90 of a friend. He didn’t used it since a few years, but was his main synth for many years and brought it on stages across Europe. Now I want to give it a second life.
Right now when I power it only the screen lights up with nothing on display.

I teared it down and figured the problem comes from the power board.
I tested the voltages (with a multimeter) based on the information from the service manual and none of them is correct.

Pin 7 is at 0V (instead of -12v)
Pin 5 at -4.9V (instead of +12V)
Pin 2 is at 0V
Pin 1 varies from 21V to 0 (sometimes lower)

I don’t have a soldering iron right now (but will get one in the next days) so I only checks the caps visually, they all seems good (none is inflated)
I know just a bit about electronics, so right now I can’t tell where the problem comes from on the board. Do you guys have any idea of what could be wrong considering these voltages ?

When I’ll get a soldering iron I will test each cap and tell you.

I suggest that for now you leave the caps alone - it’s not likely that cap failures would cause the strange voltage readings you’ve posted. I have some ideas, but I don’t have the time to help right now. I’ll hopefully be able to get back to this later today.

Hi, thank you for your answer, my other hint was a dysfunctional transistor but without any certainty.

Nat - 08 November 2020 11:50 AM

[...]
I tested the voltages (with a multimeter) based on the information from the service manual and none of them is correct.

Pin 7 is at 0V (instead of -12v)
Pin 5 at -4.9V (instead of +12V)
Pin 2 is at 0V
Pin 1 varies from 21V to 0 (sometimes lower)
[...]

Other than the “pin 1” reading, the rest of them would be what you’d get if you mis-identified pin 1 through pin 7, thinking 7 was 1, 1 was 7, etc. Yamaha boards usually have an arrow pointing to pin 1, and that should be the case on the DM (Main) board.

Also, switch-mode power supplies can become unstable if not at least minimally loaded.

I suggest that you make the voltage measurements again, after being certain of the pin numbering, and (just in case) that the power supply remains connected to the rest of the circuit.

Let us know what you find.

It turns out you were right, I tested as you said and the ps board works fine.
I first red the PIN numbers in the wrong way. There is an arrow on the DM board for pin 1 (the wire is red while others are white).
All the voltages are good with the dm board connected (I’v got 12.1V and -12.1V, and 5.0V so it should be ok I think).

I will tear down the DM board today and inspect for any anomaly, and I’m starting to read the service manual (from page 74) to eventually find the problem.

Nat - 09 November 2020 05:49 AM

It turns out you were right, I tested as you said and the ps board works fine.
I first red the PIN numbers in the wrong way. There is an arrow on the DM board for pin 1 (the wire is red while others are white).
All the voltages are good with the dm board connected (I’v got 12.1V and -12.1V, and 5.0V so it should be ok I think).

Good. In my experience, power problems in Motif-family models are rarely caused by failure of the main power supply.

 

Nat -

I will tear down the DM board today and inspect for any anomaly, and I’m starting to read the service manual (from page 74) to eventually find the problem.

You might start by looking at the Block Diagram in the service manual (page 8 in the one I have), and note that there are voltage regulators for +5A (5v Analog, IC57), +3.3A (3.3v Analog, IC2), +5PLG (5v for Plug-in board), +3.3D (3.3v Digital, IC46 and IC47), on the DM board. I suggest that you check those voltages first - if possible use an oscilloscope to verify that they are “clean”, and if not the related electrolytic caps are likely suspects.

Good news I got it working !

I think its the same problem than other people have been having here : http://www.motifator.com/index.php/forum/viewthread/478647/

After letting it plugged in for some time and reboot it, it shows the exact same error code.
I let it plugged about 20 minutes and rebooted again, with this time a error “System memory crashed.” but after closing the message everything is working great !
I rebooted it again and now its booting more quickly and without any error !

I’ll let it rest and take a look to the regulators as you said, I hope its bad caps like everyone else.
BTW your explanations helps some French people on a well know forum here, and someone even made a tutorial that I can translate if you / some people wish to : https://fr.audiofanzine.com/synthe-numerique/yamaha/S90/forums/t.655585,si-votre-s90-se-bloque-parfois-au-demarrage-une-solution.html

Congratulations!

With those messages, it’s likely that the caps mentioned in the thread you referred to are the problem.

I’m glad that my posts have helped beyond Motifator membership. Thanks for that information.

I don’t have an oscilloscope to visualize how the regulators behave, and I don’t really understand what they does anyway ahah its beyond my knowledge (D / PLG units ??).

After a few hours unplugged, it doesn’t boot the first time anymore.

I will order some good Panasonic caps and replace the suspicious ones, hoping it will solve the problem !

Thanks again a lot for your precious help, I will keep you in touch after the repair, probably next week when the shippings will arrive.

Nat - 09 November 2020 01:05 PM

I don’t have an oscilloscope to visualize how the regulators behave, and I don’t really understand what they does anyway ahah its beyond my knowledge (D / PLG units ??).

Voltage regulators such as those in the S90 output a fixed/stable voltage (such as 5v or 3.3v) when their input voltage is somewhat higher. They do so even if the current drawn from them varies (within a specified maximum range). In the S90 they serve to not only regulate voltage, but also to help isolate analog from digital parts of the circuits, in order to minimize noise from the digital section being heard in the audio output.

 

Nat -

After a few hours unplugged, it doesn’t boot the first time anymore.

I will order some good Panasonic caps and replace the suspicious ones, hoping it will solve the problem !

If the S90 you’re working on is typical, those caps will likely make the difference.

 

Nat -

Thanks again a lot for your precious help, I will keep you in touch after the repair, probably next week when the shippings will arrive.

You’re welcome. I hope things go well.

Hi there, the repairs worked ! :)))

It’s now working like a charm. I hope to get it back on the road as soon as the pandemic will be over !

Thanks to you again for your help, you rule !

Just a last thing, do you have any advice to make it work on macOS via the USB port ? I installed the Yamaha driver but nothing happens when I plug it.
https://usa.yamaha.com/support/updates/usb_midi_driver_for_mac.html
I didn’t tried with a midi interface but will do when I’ll get one if I can’t make the usb work.

Nat - 13 November 2020 01:46 PM

Hi there, the repairs worked ! :)))

It’s now working like a charm. I hope to get it back on the road as soon as the pandemic will be over !

Thanks to you again for your help, you rule !

Congratulations! You’re welcome, I’m glad the repair was successful.

 

Nat -

Just a last thing, do you have any advice to make it work on macOS via the USB port ? I installed the Yamaha driver but nothing happens when I plug it.
https://usa.yamaha.com/support/updates/usb_midi_driver_for_mac.html
I didn’t tried with a midi interface but will do when I’ll get one if I can’t make the usb work.

Presuming that you’ve downloaded the correct USB MIDI Driver for the macOS version you’re running, make sure that in Utility mode the MIDI IN/OUT setting is “USB"…
Press [UTILITY] > [F5]MIDI > [SF4]OTHER
STORE the setting if you want to keep it.

There will likely be additional settings needed with the MIDI software being run, such as ports.

After more investigation I found out that the usb connector is actually broken.
The two bottom pins (noted 3 and 4 on the connector itself) are dislodged and the “enclosure” is bent to the up. I guess someone gave a hit and broke it.

Hopefully I found the exact same part and ordered it, I hope the replacement will solve the issue.