Hello All,
I know what I'm asking here is not easy to answer but, here I go anyway. A couple of years ago I got a Roland (Sound Canvas) SC-88 Pro, 120v version, it was like new, manual, original box, everything was great, not a scratch. Played with it for a couple of months and it worked as expected. A few days ago I wanted to use it again and now the sound it's completely distorted, it's like a big crackly sound (I'm attaching a sample using the sound preview button: one short press, one long and another short at the end) .
So, I opened it up and noticed that in the main board, some of the Alum/Poly (smd) caps leaked, not a lot but they did. I replaced them (8) with spare ones I got from Digikey, nicely done, no traces lifted whatsoever and used the same values of course but, that didn't fix the problem. I got the Service Manual and compared the voltages from the transformer, there are 5 output pins as you can see in the picture. I did two tests, one with the transformer on it's own, cable disconnected from the Main board, and the second with the cable connected.
My readings with a Fluke multimeter: (AC)
with the cable disconnected from the main board:
on the 12v ones I get 16.77v each
one 5v gives me 6.22 and the other 2.17
with the cable connected to the main board:
on the 12v ones I get 16v each
the 5v are aprox. 3.98v each
Either way, theses numbers are all wrong, correct? am I missing something? I don't see any signs of heat damage or leakage (except the caps I mentioned from the Main board), everything looks good, no funny smells, etc. If the voltages are all wrong, that probably damaged some chips, right? I guess replacing the transformer would be too late... (not to mention finding a replacement).
More finds:
I tested some voltages that go to the main board and got these values: (DC) 4.9v, 3.6v, 2.48v, 0.9v, some numbers look really odd but I don't know.
In the "analog" or secondary board, the (Japanese) electrolytic caps look in great shape, no swollen or leakage. Also, I did a test with the line-in and the sound is correct, no problems there.
Midi inputs get the signal but, that's when audio gets bad, same if I press the Preview button.
Display and buttons have no problems at all.
I did some of the tests from the Service Manual and got several errors with the "Memory Test", I'm attaching a screenshot of what the manual says it's wrong, it matches exactly with what is reported on the screen. The thing is, sometimes a bad component can trigger a chain of errors which is what I think is happening here but, I'm no expert.
I looked at all those chips but I can't find broken traces or burn marks.
I want to fix this thing so bad!!
Any ideas?
Thanks for reading!
I know what I'm asking here is not easy to answer but, here I go anyway. A couple of years ago I got a Roland (Sound Canvas) SC-88 Pro, 120v version, it was like new, manual, original box, everything was great, not a scratch. Played with it for a couple of months and it worked as expected. A few days ago I wanted to use it again and now the sound it's completely distorted, it's like a big crackly sound (I'm attaching a sample using the sound preview button: one short press, one long and another short at the end) .
So, I opened it up and noticed that in the main board, some of the Alum/Poly (smd) caps leaked, not a lot but they did. I replaced them (8) with spare ones I got from Digikey, nicely done, no traces lifted whatsoever and used the same values of course but, that didn't fix the problem. I got the Service Manual and compared the voltages from the transformer, there are 5 output pins as you can see in the picture. I did two tests, one with the transformer on it's own, cable disconnected from the Main board, and the second with the cable connected.
My readings with a Fluke multimeter: (AC)
with the cable disconnected from the main board:
on the 12v ones I get 16.77v each
one 5v gives me 6.22 and the other 2.17
with the cable connected to the main board:
on the 12v ones I get 16v each
the 5v are aprox. 3.98v each
Either way, theses numbers are all wrong, correct? am I missing something? I don't see any signs of heat damage or leakage (except the caps I mentioned from the Main board), everything looks good, no funny smells, etc. If the voltages are all wrong, that probably damaged some chips, right? I guess replacing the transformer would be too late... (not to mention finding a replacement).
More finds:
I tested some voltages that go to the main board and got these values: (DC) 4.9v, 3.6v, 2.48v, 0.9v, some numbers look really odd but I don't know.
In the "analog" or secondary board, the (Japanese) electrolytic caps look in great shape, no swollen or leakage. Also, I did a test with the line-in and the sound is correct, no problems there.
Midi inputs get the signal but, that's when audio gets bad, same if I press the Preview button.
Display and buttons have no problems at all.
I did some of the tests from the Service Manual and got several errors with the "Memory Test", I'm attaching a screenshot of what the manual says it's wrong, it matches exactly with what is reported on the screen. The thing is, sometimes a bad component can trigger a chain of errors which is what I think is happening here but, I'm no expert.
I looked at all those chips but I can't find broken traces or burn marks.
I want to fix this thing so bad!!
Any ideas?Thanks for reading!
Attached Files
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