VOGONS


SC-88 repair?

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First post, by Wanny

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I'm new to this vintage hardware. I got myself a Roland SC-88 some months ago and it was working perfectly until yesterday morning...

I came back from Christmas dinner and wanted to do some stuff with it, but when I turned it on I heard a nasty static sound. If I press the Preview button I can vaguely hear a note, and if I play something through MIDI I can hear notes as well, but with the constant static noise on top.
I replaced the internal battery with a brand new CR2025 (it's the same as a CR2032 but a little thinner) since I was getting a LOW BATTERY message on powerup. The error disappeared but the noise problem persisted.

I found a link for the service manual ( here), followed the instructions for the Test Mode and...
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The blinking number is D1, meaning that one of the DRAM chips went bad. According to the service manual it's a M5M44256BJ-7 chip.

Has anyone run into this issue?

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Also, unrelated to the issue, I noticed that the transformer has many voltages (100, 230, 250, etc) next to unused pins. Is it safe to assume that I can desolder the cable from the 110 pin and connect it to the 230 one to avoid having to use stepdown transformers? (we use 230v in my country)

Reply 1 of 7, by cyclone3d

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I haven't run into that problem on a sound module.. but RAM can go bad.

If it was me, I would try re-flowing the solder on the RAM chips first. It could just be a bad solder connection.

A hot air soldering gun and some no-clean flux would work very nicely.

You will want a hot air soldering gun either way if you want to repair it yourself if a RAM chip is indeed bad.

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Reply 2 of 7, by keropi

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About the transformer - there is another thread here and it works like you say, you can move the cable to 230v and it will work. Better search for the thread but I am 99,9% sure it works like that.

🎵 🎧 PCMIDI MPU , OrpheusII , Action Rewind , Megacard and 🎶GoldLib soundcard website

Reply 4 of 7, by Wanny

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keropi wrote:

About the transformer - there is another thread here and it works like you say, you can move the cable to 230v and it will work. Better search for the thread but I am 99,9% sure it works like that.

OMG it's true. I'll do the mod tomorrow, that a friend will help me giving it a look (my soldering skills are none...)

It could be possible that the problem was caused by a bad quality stepdown transformer?

Reply 5 of 7, by keropi

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could be, cheap stepdown transformers are cr*p
I hope this solves your issue!

🎵 🎧 PCMIDI MPU , OrpheusII , Action Rewind , Megacard and 🎶GoldLib soundcard website

Reply 7 of 7, by fr0ztz

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Hi!

I'm having the same issue with my SC-88, one night last week it started to snap, crackle and pop.

Seems like the more channels playing the worse it is. When previewing an instrument I can only hear a little static noise.

I'm thinking PSU.

- Did you find out what was wrong with your unit?

Regards.