Kind of surprised you found bad caps on the SC-88 motherboard, Roland did not cheap out on them and were of good quality to begin with...
When you press the volume button in the unit is supposed to play a tone of the current selected instrument, does your SC-88 do at least that?

How did you test if I may ask? Sure the LCD might be shot but the unit could still work - I have a SC-55mk2 with a dead LCD but it works fine otherwise. Did you check for cracked solder joints on the audio/midi/knobs inputs/outputs? I'd reflow them just to be sure, cracked solder joints is a common fault as far as I've seen : the toll of years of plugging/unplugging the unit 🤣

Thank you for the reply keropi,

I checked the solder joints on the headphones and the front panel everything looked good, pushing the volume knob in does nothing.
I did reflow as per your suggestion as it was a good idea, but eh still nada.

Then I fear my friend something more serious is going on... because when you press the volume button it is supposed to play a note, this is called the "Preview Function" on the manual - something to check volume level I suppose. If the SC-88 cannot generate this simple tone I am not sure what could be wrong , maybe the psu fault killed some important component or something...
Another easy check if you have a programmer, see if you can read OK the 27C4096 eprom at IC17 , it's the device's firmware. Maybe it is dead/faulty and that would explain why the SC-88 is a brick.

Also do an inspection of cut or corroded traces , maybe something is not connected. I cannot think of anything else to check atm, if the damage is more serious (ie a dead cpu or other custom roland chip) I fear there is not much to be done 🙁

Your right,

I tried my hand at google.co.jp and google translate. first post I got was the identical problem i'm having.

Using google translate, I understood that there was a main cap on the analog board that ate away a trace from the test point back.
I tested mine and yep no connectivity. so i put a wire on it and nothing again.. 😒
I even replaced that cap.

I think i am going to have to replace all caps and check a lot of traces.
as Luck would have it I did just get an ic programmer in! its a great idea and i will check it when i get to work tomorrow.

website for anyone else interested.
http://blogs.yahoo.co.jp/ko_u_he_i11/26642396.html

well today I checked the eprom and there was data on it but i have nothing to reference it to.

if anyone knows of a location for 1.01 rom i can cross reference with mine to make sure its correct that would be cool.
I went through and double checked all the replaced capacitors to make sure they had continuity between them and the traces, all tested good.

did some more digging on google.co.jp, nothing new...
man this thing is tricky... :\

It sure is... I don't have a SC-88 else I'd read the eprom so you can compare. This is just a case of searching until you find the fault , a very tricky situation.

Quick update,
I bought every electrolytic capacitor and replaced all but the output caps and still no change.
So I think I'm left with bad traces or a bad chip somewhere.
🙁 guess I will start with the chips should be easier then the traces?

I hate to say it, but having a good working unit can make troubleshooting a lot easier (then you can swap components between the two and easily narrow it down).

Did you verify the SC-88 EPROM was good? If not, all troubleshooting will have to wait until you put a good eprom image.

Judging from what I see on the SC-88 screen it's not even initializing (and if it's not initializing, then it's not going to play any of its ROM sounds). So, the issue isn't that it can't play sound, but because it's not processing anything TO play sound.

Thank you for the reply raymangold,

I completely agree that it would help! I have setup a thing on ebay to tell me when one pops up for cheap.
funny thing is another unit with the exact same problem is up there right now, I thought about buying it but that seemed silly.

I did say that I checked the eprom and it does have data, but I have nothing to compare it to see if its good.
I'm still looking to see if I can find a dump of the rom but Its not looking good.

I agree that it is not initializing, and with all the things I have done so far I think i'm down to bad data on the eprom, a bad trace, burned out logic chip's, or a dead cpu.

I will do my best to keep this up to date because it is the top hit on google for "sc-88 fix" and hopefully it will help someone out!

Hi all,

Took a logic probe to some of the main board today most of the ic's I tested checked out but I did find some odd ones.

IC 16 and 21 were acting odd, using a logic probe on ic 16 pin 6 gave me a low pulse and on pin 2 its output; gave me just a low. according to what I have been reading this is way wrong.
the chip is a triple inverter, so going from in to out should make the signal go to its opposite.
i.e. high input would be low output.
these two ic's are in line with the cpu and custom sound generator chip clocks.
the cpu clock has a low pulse in but a low pulse out, again if I'm reading things right it should be high pulse out?

I think I am going to order these and see if replacing them helps unless anyone has any other ideas on this.

I also read somewhere that the reset signal from the analog board should be 0v's for 5 seconds then 5v's mine just stays at 5v...

laters

GoXoD wrote:

Took a logic probe to some of the main board today most of the ic's I tested checked out but I did find some odd ones.

What kind of logic probe is it?

GoXoD wrote:

IC 16 and 21 were acting odd, using a logic probe on ic 16 pin 6 gave me a low pulse and on pin 2 its output; gave me just a low […]
Show full quote

IC 16 and 21 were acting odd, using a logic probe on ic 16 pin 6 gave me a low pulse and on pin 2 its output; gave me just a low. according to what I have been reading this is way wrong.
the chip is a triple inverter, so going from in to out should make the signal go to its opposite.
i.e. high input would be low output.
these two ic's are in line with the cpu and custom sound generator chip clocks.
the cpu clock has a low pulse in but a low pulse out, again if I'm reading things right it should be high pulse out?

Those chips, IC16 and IC21, are not used as traditional logic inverters. They are "unbuffered" logic inverters that are especially suitable as analog amplifiers in a crystal oscillator circuit. Sometimes, even a 10x oscilloscope probe can prevent the circuit from oscillating properly, so you are best to measure anything from IC16 pin 2, or IC21 pin 2, but only if you can measure up to 25 MHz signals. I bet your logic probe is just unsuitable for this.

GoXoD wrote:

I think I am going to order these and see if replacing them helps unless anyone has any other ideas on this.

No, don't replace them, most likely they are just fine, if you check it with good enough tool.

GoXoD wrote:

I also read somewhere that the reset signal from the analog board should be 0v's for 5 seconds then 5v's mine just stays at 5v...

It's more like 5 milliseconds than 5 seconds.

I'd love to know how you came to the conclusion "bad caps".

Good question shock,

On the Main board all of the smd capacitors had residue next to them and the solder pad looked dull gray and cloudy.

this is a pic of some one else's but the top cap shows what i saw on every cap on the main board.
also on the analog board i saw some shiny clear liquid next to one or two caps and assumed that was also electrolyte leaking out.

So rather then dealing with a pain that might cause more damage later I chose to remove all capacitors, cleaned the board best I could and tested continuity which checked out.
unfortunately I do not have an lcr meter to test all the caps, but I figured I might as well spend the money and replace them all considering the unit is more then 20 years old.

so while i will say the might have all tested out on a meter and most did with my dmm it was more of a preventative measure.

Off topic, I cant wait to see your guspnp it looks like a great project and hopefully i will have money when time comes to buy one!

Okay, that looks like legit capacitor damage (I think the mania to swap every electrolytic cap asap is one of the worst pests that was been around in retro communities). Did you test the pads/signal lines for conductivity? Often they still look good but are actually broken.

Otherwise: Did you check if the SC-88 is completely dead instead of maybe just the LCD? That way it would be a lot easier to find the issue.
Another thing to check would be if all voltages get to the chips - if that is okay you can start checking the digital part, whether various control signals (i.e. reset) are present.

Ya I went through again and cleaned the smd caps one last time testing conductivity on each trace on the capacitors all checked out good.

I believe what the lcd is displaying is what happens when the unit cannot boot up correctly.
I checked the 5v, 12v -12v and test rails they seem to all check out.

The only odd things i have found so far is on the cpu pin 58 marked as P42/TNRI has no digital signal, no lo no high nothing...
also the clock for the custom sound generator seems odd, if i take my oscilloscope to the output seems correct but when using my logic probe its just stuck low.
idk whats up with that as the clock on the cpu seems to output correctly on both.

I tried swapping a tc7wu04f that tested correctly from ic 1 to ic16 hoping that would make the clock "act right" but that did nothing...

I am getting to the point where I am thinking of buying another one.. 🙁

What's the signal level for the clock? TTL or just a crystal with pull capacitors? If the later your logic probe might add a load that's too high to drive for the circuit.

Is there a schematic and/or datasheets around?

Crap i totally forgot that it might be adding that load, I was just thinking well the other clock works with it....
It is a crystal with caps, on the oscilloscope it seems to be real close to the right mhz, its hard to tell with my old analog scope..

here is a link to the pdf I am using, http://www.synfo.nl/servicemanuals/Roland/ROL … RVICE_NOTES.pdf
The schematic is on page 13 and the crystal in question is at K-23.

I'd say first check if a !RESET signal is generated (should go from 0V to 5V and is connected to various chips) ... if that's the case chances are good the CPU(s) are working. In that case a repair might be worth a shot.

Yep reset is 0v when off and 5v "4.943" when on, tested at pin 1 cpu, pin 54 on custom sound generator chip, pin 20 on the ic 11, and pin 65 on ic 27.
Side note the Custom sound generator chip gets really warm.

Thank you for the reply's on this.