Blown cap on my Roland SC-88 (pictures inside)

Discussion about old sound cards, MIDI devices and sound related accessories.

Blown cap on my Roland SC-88 (pictures inside)

Postby Woolie Wool » 2019-1-10 @ 04:48

A couple weeks ago, during a Doom session, I started hearing a strange crackling from my Roland SC-88. Initially thinking it to be a problem with my DAC or the Toslink cable I was using, I fiddled with the cables of my audio setup several times before resuming. Then, in the middle of a fight, I heard incredibly loud digital crashing and grinding noises...and the music stopped. Ever since then the DAC has produced nothing but static crackling with the occasional burst of distorted music before going back to crackling again. I initially thought the analog board was at fault, disassembled the machine, and checked all the capacitors. They were perfect, and there were no signs of damage to the board. Furthermore, the SC-88 works fine as a preamp for an audio source and the diagnostic routines indicate errors in...the MIDI engine? Uh-oh.

So then I started googling people who had problems with their SC-88, and found this story. This guy's problem was on the digital board. It turns out a capacitor labeled C38 had blown, so I brought mine out to my workplace where the lights were much brighter at home, and conducted some exploratory surgery.

It's C38. The very same cap as that guy's problem. It blew and spewed a bit of cap juice. The capacitor C39 and the chip IC22 may have been contaminated by electrolyte and damaged, but it's hard for me to tell.

Pictures (click to embiggen):

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Overview and analog board.

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Digital board. Wait, what's that? Let's take a closer look.

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C38 and electrolyte bukkake.

So now that I know what the problem is, what to do? I'm unfortunately not particularly great with my hands and have no soldering expertise. I do, however, have the machine itself, the service manual, records of all the diagnostics I ran, and someone else's example of how to fix this problem. Is there anyone here who might be able to point me towards someone who'd be willing to take on repairing this thing? I'd hate to throw it in the garbage and get a new one, even though it might cost me less in the end.
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Re: Blown cap on my Roland SC-88 (pictures inside)

Postby cyclone3d » 2019-1-10 @ 05:35

Where are you located?

That is literally like a 5-10 minute fix.
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Re: Blown cap on my Roland SC-88 (pictures inside)

Postby Woolie Wool » 2019-1-10 @ 14:06

Memphis, TN.
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Re: Blown cap on my Roland SC-88 (pictures inside)

Postby CrossBow777 » 2019-1-10 @ 19:12

Woolie Wool wrote:Memphis, TN.


When you do get this fixed, I'd replace all of those surface mounts with either brand new surface mounts or if space allows, radial electrolytics like what is used on the analog board.
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Re: Blown cap on my Roland SC-88 (pictures inside)

Postby cyclone3d » 2019-1-10 @ 19:20

Woolie Wool wrote:Memphis, TN.


Ok, so not that far away from me. In any case, it would probably be just as cheap and a lot quicker to have a local electronics repair shop replace the cap(s) for you.

Here are a couple that get good reviews on Yelp!
https://www.yelp.com/biz/digitech-electronics-repair-memphis-2

https://www.yelp.com/biz/electronics-repair-center-memphis-2

I would call them up and tell them what you need and ask a range of how much it would cost.
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Re: Blown cap on my Roland SC-88 (pictures inside)

Postby Woolie Wool » 2019-1-12 @ 00:22

I called up the former of those two shops and I'll be taking the SC-88 and service manual in tomorrow. Thanks!
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Re: Blown cap on my Roland SC-88 (pictures inside)

Postby pentiumspeed » 2019-1-12 @ 00:59

The guy who replaced that C38 capacitor (due to new shiny solder with brown hard solder flux around it) forgot to clean up the former old capacitor's corrosive goo and repair traces and vias around C38. You'll have corroded traces and vias as I can see the vias and copper square that marks one corner of chip is corroded away. That need to be redone. And very smelly when soldering those. Scent of rotten fish.

I have done this all the time on PIP boards for certain brand TV and other brands that used corrosive capacitors I had to repair any that were eaten away that a decade ago when I was a TV tech repair person. My current job fixing cellphones but no corrosive stuff except for any that took a dive can be treated and repair if any found, yet there is difference is everything is done with microscope. :)

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Re: Blown cap on my Roland SC-88 (pictures inside)

Postby Woolie Wool » 2019-1-14 @ 15:10

The SC-88 is in the shop now. There was a mixing console and several other pieces of complicated audio equipment in the store's atrium, so if anyone can fix this thing, Digitech probably can.
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Re: Blown cap on my Roland SC-88 (pictures inside)

Postby Woolie Wool » 2019-1-21 @ 04:37

Digitech repaired the SC-88 and it's working fine now! Thanks to Cyclone3D for the Yelp link.
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Re: Blown cap on my Roland SC-88 (pictures inside)

Postby cyclone3d » 2019-1-21 @ 05:07

Great to hear that it is working now. You're welcome for the link.

I really need to look up repair places in my area at some point as I have a Yamaha DX7II-FD that will no longer power on. I already replaced all the caps on the power board as well as a couple diodes that seemed to not be working properly but it didn't fix it... bleh.

I did't use it for about 6 months or so and then when I went to power it on.. nothing :depressed:
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