Japanese Parts/Chips etc

[ericcoleridge]

I've got a non-functional Korg tape delay just sitting around waiting for repair. I've tried replacing all kinds of parts, but I can't get it working. It's an electronic problem, not mechanical.
I've wondered if maybe the western substitute parts I've used are what's keeping it from working. There's an "MSM551" and "MSM4017 which I think are both CD4017s, and there's a "MSM4066", a CD4066. But I have no way of knowing if they're exactly the same.

Anyone have any experience with this Korg, or these Japanese parts?

[Clack]

Only Datasheets will really give you a clue to how similar they are if at all and it seems like they are thin on the ground.

got a schematic?? context helps

[jordroid]

Interestingly, a buddy just dropped a korg se-500 stage echo off with me to see if i could fix it. I haven't gotten anywhere with it yet, and i'm not certain i'm up for it, but it's kind of fun that we both have them at the same time.

I have not had luck (yet) finding a schematic or much of any information on these, the owners manual is easily findable but doesn't have much information you couldn't figure out just by looking at it.

I'll keep you posted if i figure anything out, please do the same if you locate a schematic or discover anything illuminating.

I believe my problem may be with the heads or circuitry for mixing in the repeats, as one head sounds great and does what it should, while the others do something but not much, you can hear a faint repeat or two but no dramatic echo and no avalanching echo oscillation. I have so far not done much more than verify that it is indeed not working correctly.

Anyways, good luck

jordan

[ericcoleridge]

[andrewF]

I have some interest in this thread, my SE500 still works fine but its only a matter of time 'til something gets too old. Be good to see the schematic and between us we might be able to work out the problem.

I'm don't think the MSM551 is the same as a 4017. Its BCD rather than pulsing outputs Q0-Q9, the 4029 can be configured as a BCD decade up counter.

[billfusion]

Have you tried looking up a schematic for a standard tape deck, and also look at standard tape defect help list.
Also I do know of some tape heads being fixxed by a claning and remember radio shack having a minidemagtizer for old day tape decks

[ericcoleridge]

[billfusion]

Know what Les Pual's best invention was?
I am an electronics tech and one problem that affect some circuits is flux, so be sure to usew some ispropol acholl to clean area after doing re-work.
you would be surprised how many boards i have fixxed doing that. Plus I do know older circuit boards used a heavy rosin core flux, nice but it leaches ans have fix some old stuff by reflowing and clean

[ericcoleridge]

Korg SE500 Schematic, part 1 and 2.

If there's a better place for me to post these, let me know, and I'll move them.

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[jordroid]

Thanks Eric, much appreciated.

I seem to have "fixed" mine by simply taking it apart and putting it back together, and cleaning the heads a bit. I'm not super confident that it will stay fixed but it is sounding much better, for now.

thanks and good luck,

jordan

[monotron]

I seem to have a similar problem with my SE500.

I can hear a little bit of echo, but the volume is very low, the sound is very dull and I can hear maybe two or three taps of echo.

Ít could be the tape that needs replacement, or demagnatising the heads.

Anyway, if you solved your problems, i'd like to hear wath your solution was.
I disassembled mine yesterday, but that didnt do the trick. It actually made it worse. The motor is not running now, so i hope thats a losse connector or something.

Thanks
Walter

[monotron]

Update;
I checked for loose connectors and indeed, the connector to the motor was loose, so that was an easy fix.
I demagnetised the heads and other metal parts along the tape path. I also cleaned the heads again with 97% alcohol.

I have a somewhat normal echo right now. The feedback is still not at its maximum potential, but the tape is really old and thus crap. I have to order or make a new tape and i guess that will solve the rest of the problems.

[ericcoleridge]

I basically did the same thing with mine when I first got it; cleaned the heads, sort of adjusted their positions for maximum volume and clarity, changed the tape, fooled around with the repeat gain a little. It all helped a lot briefly, but then the echos started losing volume again. It was incredibly annoying.

I keep meaning to bring it in to a shop, but I live in NYC, and rent is out of control, I never have the extra money. But when I do, I'll ask the repair person what the problem was and hopefully shed some light on this machine.

[monotron]

That must be annoying, assuming all is ok after some cleaning and maintenance, but later the same problems rise up again.
I hope you´re able to find a good repairman and fix your Korg asap!

I also hope mine stays good now. It was a really big difference in sound by only demagnetising. I didnt expect the difference to be that big.

I´ll have look at your schems, to see where the feedback trimpots are, maybe i can crank it up a bit.

[monotron]

I inserted a new tape today. It's not new, but it looked like it was unused. It's a RE-201 rt1l tape. Bu somehow the korg has less echo again.

I tested a sound on sound loop, but the volume faded away. I took about 5 loops of the sound to totally disappear. I have to look into this.

It might be the erase head, who's erasing the tape slowly, but i'm not sure an erase head can 'partly' erase the tape so volume is less. I'd guess an erase head either erases the tape totally or it doesn't erase at all.

It might be the Korg is somehow magnetizing itself and thus erasing the tape slowly with each loop of the tape being played.

I'll try and demagnetize it tonight again and do the test immediately afterwards. If volume is back to normal I think the machine is magnetizing itself....

DAMN!!

[ericcoleridge]

I think that I remember the Korg asks for a different kind of tape from the Roland. But, I wouldn't think that it would make a drastic difference were one to use the "wrong" kind of tape-- I think it would be more subtle.

[monotron]