I hope you get your S90 to behave. Let us know how it goes.

KSUS - 15 February 2017 10:42 AM

Hi 5Pin,
I’d love to see a reply from tertiumsquid also how he exactly found out what caused the problem, but I can imagine since his S90 is operational he won’t check the forum lately.

Haha yeah, I’m not much of a forum guy - I’m a member of probably a hundred forums out there, with probably an equal amount of total posts between them!  But yeah, my S90’s been behaving perfectly since I was last here, so I haven’t felt the need to be back.  Of course, I am subscribed to the thread (which doesn’t seem to email me all the time sadly).

I’ll actually probably be posting back here again, as a friend of mine also has a wonky S90 with the same problem - we got them from an audio engineering school who were selling off the working ones and tossing the bad ones (they had I think 18 total).

I found the problem by looking at the ripple voltage on an oscilloscope.  A really crappy one did the job - mine was a kit costing $60 (link), though it honestly is terrible even for occasional novice use.  I plan to get a MUCH better one when I have money to spare.

The points I checked and had problems at were at the caps 5pin and I mentioned - C9, C124, and C125.  As he mentioned, this might not fix your problem, as it could be something further upstream causing issues, all the way back to the +5v at the main power supply.

KSUS - 15 February 2017 10:42 AM

Is there a way to detect the ripple with that $10 tool you referred to?

The tool 5pin was referring to is one that will measure the ESR of the capacitor, but only once it’s removed from the circuit (presumably).  With the surface mount caps, you certainly don’t want to pull each off one by one to test them.

KSUS - 15 February 2017 12:51 PM

Thanks again 5Pin.
I will replace the the caps at IC46, IC47 and IC2. (after measuring them.)

I have a feeling it will fix it. I will replace them with radial lead capacitors if it got the space. If not, youtube is providing enough help to fix it this weekend.

Measuring the caps in and out of circuit didn’t do anything in my case - the ESR testing I tried didn’t show anything unusual at those caps, and even when I pulled them out they still measured 47-50uf.  Bad ripple voltage was the only indicator that something wasn’t working.

I replaced mine with regular radial caps after removing the bad ones.  I found the best way to remove the SMT caps was to wiggle them gently until the leads eventually broke, then I cleaned up the solder pads and “surface mounted” the radial caps. 

KSUS - 15 February 2017 08:34 AM

looks like you totally know what you’re talking about

Hahahahaha yeah I try my best!  I do have a certificate in electronics production and repair, though I certainly find a great many gaps in my knowledge.

Hi Tertium,

Thanks for your reply :)

I’ll actually probably be posting back here again, as a friend of mine also has a wonky S90 with the same problem

I’m curious what the problem is at this unit, I’d like to know when you got it fixed and what caused the problem in this case.

The points I checked and had problems at were at the caps 5pin and I mentioned - C9, C124, and C125.  As he mentioned, this might not fix your problem, as it could be something further upstream causing issues, all the way back to the +5v at the main power supply.

Well, I guess I will just try to replace this ones first.
Did you order the caps online? What brand/type did you use?

Reg,

Kees

I think we can delete the user with the ads here..

KSUS - 21 February 2017 11:11 AM

I’m curious what the problem is at this unit, I’d like to know when you got it fixed and what caused the problem in this case.

I’ll definitely keep this thread up to date when I get my hands on it.  That may take a while though, as my friend is coming up on the end of his school term and is quite busy.  He’ll get a break in about 3 weeks, so we’ll probably look at it then.

KSUS - 21 February 2017 11:11 AM

Well, I guess I will just try to replace this ones first.
Did you order the caps online? What brand/type did you use?

I just used cheapo caps I had kicking around here.  I think they were G-Luxon.  Admittedly they’re pretty crappy caps, but I did test them for ESR with my scope, and they are working right now.  I’ll get better caps in there when I do another Digikey order.

tertiumsquid - 23 February 2017 08:34 AM

I just used cheapo caps I had kicking around here.  I think they were G-Luxon.  Admittedly they’re pretty crappy caps, but I did test them for ESR with my scope, and they are working right now.  I’ll get better caps in there when I do another Digikey order.

Even if the G-Luxon caps are OK now, I’d suggest not waiting too long to replace them. Many of that brand of caps were notorious for failure, although the problem was more prevalent several years ago.

http://www.google.com/search?q=g-luxon+bad+caps

As we previously discussed, Panasonic/Matsushita tend to be reliable. There are others, but Panasonic ones usually are readily available.

Superb, thanks guys. Your help is great. I will solder some new pots in my ghost mixer this weekend and maybe I will open up the S90 to if I got some spare time.

Hi fellow S90 users,

My S90 was suffering with system down error messages on power up with various unrecognised interrupt addresses reported. The problem was worse on cold days and sometimes took several startup attempts before starting successfully. It made me nervous and I worried that one day I may not be able start at all. I was already looking around for another keyboard.

Then a few days ago I found this thread with a possible solution.

Without bothering to run any tests I just opened up my S90 and soldered in the 3 capacitors as specified in this solution. I didn’t remove the existing capacitors - just bridged a radial capacitor across each one right next to the original. There are convenient solder points on each side of the existing capacitors and you just need to be careful with your soldering iron as the points are fairly small. I used 47mf 16v caps that I happened to have in my parts cupboard.

Anyway I just wanted to report that this solution has fixed the problem on my S90. It now starts up first time every time even in the current cold weather.

Thank you so much for posting this solution.

ricksz - 05 July 2017 12:36 AM

[...]Thank you so much for posting this solution.

You’re welcome, and thank you for posting your own experience with the repair.

My unit fixed itself. The error disappeared after a while. Maybe moving it caused it?? I rather check the unit again.

Indeed, it’s getting cold. The unit won’t boot at all and I really have to repair it now. No other options, I can’t miss this unit. The keys are so soft and smooth and the sound I’m in love with.

Any downsides on the method Rick is using? It a lot easier to just solder the new caps along the old ones :).

Anyway, I will report soon on how it went. I already bought a korg unit but it’s just not like this s90.. :(.

KSUS - 20 February 2018 11:18 AM

[...] Any downsides on the method Rick is using? It a lot easier to just solder the new caps along the old ones :). [...]

While it’s not my preferred method, leaving the bad caps in place and paralleling them with good ones can work. You don’t have much to lose, other than time, as long as you work carefully.

Hi...i am a new user here. As per my experience it seems the issue is related to power supply, and capacitors would be my primary focus. Caps that are used for decoupling in digital circuits need to have low ESR, so hopefully the ones you used as replacements fit that requirement.

pcb fabrication

CoraDias - 04 April 2018 01:50 PM

Hi...i am a new user here. As per my experience it seems the issue is related to power supply, and capacitors would be my primary focus. Caps that are used for decoupling in digital circuits need to have low ESR, so hopefully the ones you used as replacements fit that requirement.

You may be a new member, but you’re likely a SPAMMER doing a test post. Otherwise, why is your post just a copy of content from a previous post (by me) in this thread?

Hello everyone. I too am having the same power on issue with my s90 and suspect the similar components are faulty. I wanted to know what places is best to order the voltage regulators and which type is recommended. So far I have ordered parts (electrolytic capacitors and currently looking for SMD chip-type capacitors) from eBay and Amazon. I had tried to order the parts via Yamaha’s support site but I haven’t had any luck especially using the correct part number references from the service manual. Any info would help.

Thanks