Like "very warm" or unbareable to touch within seconds?

IC11 and IC27 seem to be reliable for the LCD display, anything weird on any pins there (haven't extensively checked the schematic yet)?
Also the PROM would be a potential candidate for dying of old age.

very warm, then goes cold after a min or so..
so i was poking around those two chips and i accidentally had my dmm set to continuity and it beeped when it was on the 5v!
I was like what?? so i tested down on the power board, when the power button is on 5v and 12v have continuity, -12v does not...

so i disconnected the main board and i still got continuity, Im going to keep poking and report back.

Also I looked at the eprom and downloaded the code that was on there but i have nothing to compare it to, to see if the code is good.

OK wtf am I doing wrong?
I just unplugged the transformer and tested continuity between gnd and the 2 12v on it when the power is on, and its showing a short...
i did the same with the 2 5v and it does not show a short...
also both 12v show about 16.281 give or take.
on the 5v side, one is showing 2.242v and the other is showing 7v..

This is not normal at all right?? i feel like im going nuts.

GoXoD wrote:

Also I looked at the eprom and downloaded the code that was on there but i have nothing to compare it to, to see if the code is good.

There should be at least some kind of copyright message in plaintext there, if it's good and no suspiciously large areas are either just 00 or FF it should be okay. When in doubt, maybe generate a checksum and post it here (posting the full file probably violates some copyright).

Transformers usually have a higher voltage (like 20-30%) when no load is connected (don't know the correct english phrase). So the 16.2V & 7V seem alright.
The 2.2V is way too low tho.

I think I was chasing my tail on the transformer, when i connected it back and checked the voltage it was reading 5v's on both 5v lines...
i don't know ac that well at all.

I dumped my file last week https://drive.google.com/file/d/0ByWBJRdMFXAz … iew?usp=sharing checksum E541511ECE15A3027C0A06DEED6F0B27
I don't think it would violate any law it would be the same as dumping a bios would it not?

If i am wrong on all of this just tell me and I will pull the file.
there is a lot of empty space in it though.

I hope some one can compare this to theirs..

Hard to give an estimate based upon that dump ... might be good, might be bad, might be incorrectly dumped.

I just checked that file against a new dump and it verified good. I am using a minipro tl866cs with the software provided.

Found this @ 13020h

1....@B.@ -OSNU DaCvnsa- ........

Looks suspiciously like a scrambled "SOUND Canvas"

You either selected a wrong ROM type or your rom might be partially bad (scrambling might be realized in hardware as a low level copy protection). What type did you select in your programmer?
Comparing it to the MT32 control ROMs there should be at least some plaintext in the ROM file.

EDIT: Try Hitachi 27C4096 as the type ... that one seems to match the pinout from the schematic. If all else fails try MB834100 or KM23C4200

shock__ wrote:

Found this @ 13020h […]
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Found this @ 13020h

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1....@B.@ -OSNU DaCvnsa- ........

Looks suspiciously like a scrambled "SOUND Canvas"

You either selected a wrong ROM type or your rom might be partially bad (scrambling might be realized in hardware as a low level copy protection). What type did you select in your programmer?
Comparing it to the MT32 control ROMs there should be at least some plaintext in the ROM file.

The H8 is a big-endian CPU. I'd suspect that is normal. Just swap bytes within a word.
Anyway there seems to be data.

Morning,

The ic I selected was HN27c4096H I even tryed the HN27c4096G and HN27c4096 and they all dumped the same code.
Nether one of those are options when i search devices in this program.
I downloaded HxD to look at the code outside the programmer but it does not line up correctly im not sure what settings im missing.

but i have found some plain text..

sorry its not bigger i'm on my laptop.

mkay ... dump you uploaded differs then. But if you found plaintext in your programmer that's good enough - chances are high it's working correctly.

Next step would be checking if there's activity on the data & adress busses and if there's any activity on pins 1-7 & 77-80 on IC27 (LCD data + controls)

shock__ wrote:

mkay ... dump you uploaded differs then.

Not necessarily. The screenshot is just displaying in word mode. So bytes within a word are swapped to make it human readable.

If the bytes in the file are 0x53, 0x47, 0x36, 0x2D = "SG6-", which in words is 0x4753, 0x2D36, and if the letters are printed most significant byte first it reads "GS-6".

Jepael wrote:

shock__ wrote:

mkay ... dump you uploaded differs then.

Not necessarily. The screenshot is just displaying in word mode. So bytes within a word are swapped to make it human readable.

If the bytes in the file are 0x53, 0x47, 0x36, 0x2D = "SG6-", which in words is 0x4753, 0x2D36, and if the letters are printed most significant byte first it reads "GS-6".

True ... turns out I totally forgot/overlooked that and being the way you describe it I can get plaintext that makes sense 😉
Therefore let's assume the ROM is working correctly.

Any progress checking the adress/data busses and LCD signals?

No sorry, I won't be able to check that until Monday I left the rest of the unit at work, and I have been super busy this weekend.

good morning all,

Using the Logic probe pins 1-7 are high pins 77, 78, 80 are high and 79 is low..
no pulsing..

I checked the input signals from the cpu, and they look like they are working. "lots of activity"

so with this we would assume that either this chip gets halted on boot?
or is dead. 🙁
If its toast I think that might be the end of this unit. I did some searching and its a custom chip, the closest thing i found was uPD65622GK-Y16-BE9 and I cant tell if they are compatible.

the data sheet is no help.

Hello everyone, first of all sorry to the OP for hijacking this thread and not adding anything to solve his issue, but as he said it ranks high in search and with this newly found cap plague on the SC-88 I believe it will continue to be relevant in the coming years as well.

After seeing this thread I inspected my SC-88 and found all 5 10µf surface-mount caps to have leaked, so I decided to give a recap a try even though it was working without issues until that point. I removed all of the caps with hot air (I used 300°C, which did cause the surrounding ICs to get hot for a moment, even with the smallest nozzle available) and when testing they had near zero capacitance left, so it is quite surprising how the machine could still function in that state. I couldn't get the 100µf cap off with hot air and tried it with pliers, and unfortunately lifted the positive pad and adjacent traces on C38; I reconnected this with a wire to pin 5 on CN1, and also connected the neighboring C39 to the new cap.

Having replaced all the caps I put it back together and it came up with a blank screen on first powerup (not like the OPs one with the black boxes though, it was completely blank), but after that worked fine with a quick test. I found my initial soldering work to be too shoddy to leave it for good, so I decided to redo it. Putting it back together I made the mistake of not connecting the CN3 ribbon cable, so it powered up with the LCD off; when i corrected this and first turned it on it would somehow jump to the test tone pitch setting, but not react to any input. Since then, it seemingly powers up normal, showing the SC-88 writing and listing these few settings, and stays on part 1 with stock settings, but reacts to neither of the front buttons nor MIDI input 🙁

I have really no idea what happened as it did work fine after the first try, could that loose ribbon cable have shorted something on the board possibly? I don't have any other explanation right now but I could get a cheap logic probe if it helps with troubleshooting. Or maybe it could be some kind of damage on the internal connectors from all the unplugging? I already checked continuity on all caps and that's not the issue, also checked the ICs for possible bridges. All of the ICs stay cold when powered up, only the tone generator IC gets very mildly warm to the touch. Quite a long shot but any ideas would be appreciated...

so uh... it was working but you decided to shotgun all the caps, rip a cap off with pliers pulling up a pad and or tracks.. then when you put it back together its not working correctly. sometimes I think people should have a license to use a soldering iron.

the only think you can do is check your soldering, see if you bridged any pins and re seat all the connectors.

Don't worry about hijacking, I wanted this to be a reference point for people to look at when repairing there own units.

That being said, heed bloodycactus's warning, do not rip off caps if the unit is working, you can just clean the whole board.
caps that have leaked make the solder harder to work with because of the chemicals, in my experience I have cut the cap off the board with out damaging the pads.

After that cleaned the solder, removed the solder, clean again, this method might be incorrect but it has worked best for me.

What would be ideal for this would be an lcr meter so you can test your caps in circuit.

So After reading through your post soundspectrumCX like bloodycactus said, check connections, is the midi input only the front or the rear as well?
does pushing the volume knob give you a test tone?
on the digital board cn4 and cn6 go to the switch board cn6 is responsable for the switchs working, and cn4 is for the lights.

with out a logic probe this might get difficult to figure out.

Hi all,

Well after an extensive search on alibaba, aliexpress, tabao, and talking to digikey, mouser, newark, nec, and renesas "took over nec ic manufacturing" reps I am at a loss for finding a replacement part for ic27 "uPD65622GF-138-3B9" on the sc-88.

This ic was a custom chip made by nec and is used in the sc-88, vl, pro, and a few keyboards.

if anyone has any further thoughts on this please post them, I am still around.