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Author Topic: Casio SK 5 - not exactly dead HELP!  (Read 2425 times)

wax+wire

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Casio SK 5 - not exactly dead HELP!
« on: February 19, 2015, 10:41:33 AM »

hey

so in an attempt to cut down some power hum noise in my casio i've managed to make it not work too well.

the sound that comes out is a 'permanent bend' type sound.  only the piano sound makes a noise.

i've unhooked all my bends (quite extensive - patchbay, slow AD mod, tuning systems, vibrato) - and it is still there.

My first guess was a poor solder connection, or a solder short - but it doesn't look like it.

I am wondering, if there is a chance i've fried an IC?  They seem pretty hardy, and it still makes a sound.

Any other tips on getting it back to life.
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wax+wire

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Re: Casio SK 5 - not exactly dead HELP!
« Reply #1 on: February 20, 2015, 08:23:27 AM »

After a bit more prodding it seems that the ROM chip's pin 25 does unusual things.  These pins have been bent through a patch bay construction - but usually no issues there.

The Rom chip is NEC D23C256EAC

I have all the normal pins connected to my patch bay except 25.  The piano makes a glitchy noise, but all the other tones are dead.  When I solder a piece of wire to Pin 25 it goes all weird (bent type sounds).  When I ground pin 25, some of the previously dead sounds (vibraphone, dog) reappear. 

can a ROM chip get confused?  could part of the chip be dead and the rest ok?
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wax+wire

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Re: Casio SK 5 - not exactly dead HELP!
« Reply #2 on: February 22, 2015, 08:15:15 AM »

sorry for the desperate cries for help.  it is my main keyboard in my band, and a gig is approaching...

I made a video of the problem

https://www.youtube.com/watch?v=aHG-d2XYYFI&feature=youtu.be
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jepyang

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Re: Casio SK 5 - not exactly dead HELP!
« Reply #3 on: April 10, 2015, 12:28:25 AM »

Just thought I'd throw it out there: when you say it doesn't seem like a bad solder connection, what is that based on? Visual inspection or actual probing with test equipment?

I only ask because I somehow killed voices 2-4 on my SK-8. I figured the only possibility was that I had spilled solder somewhere and caused a short, but after several days of searching, found nothing. I had only soldered three things to the board, but went ahead and removed them, just in case.

It was only once I went in with my multimeter to start testing for continuity that I found the problem. One of those joints had been heated and reheated too many times and a trace had imperceptibly lifted. Put a jumper in and everything was gravy. My job was easier than yours because it was at least in the analog section of the machine, which meant I could follow signal flow by actually listening, but it may be worth a shot, especially if you have a scope and can get a better idea of what is flowing where.

On the other hand...maybe it is just a scrambled chip.. :( Saw you moved over to an SK-1 so hopefully this isnt as big of a deal anymore.
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wax+wire

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Re: Casio SK 5 - not exactly dead HELP!
« Reply #4 on: April 10, 2015, 09:36:02 AM »

thanks.

yeah, i'm playing the firstt show tonight on the sk1.  hopefully it will last the show!?!?

i've removed all the bends and contraptions, and it is still not working, but i'll give it a go over with my multimeter soon.  I really hope I can revive it, as it was/is a beautiful sound source
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wax+wire

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Re: Casio SK 5 - not exactly dead HELP!
« Reply #5 on: May 08, 2015, 08:16:00 AM »

Thanks Jepyang,

All the connections seem ok with a multimeter.  So I'm not sure there.

I've just got myself another SK 5 (this time a casio, not a concertmate).  Any thoughts on how I could use a working casio to troubleshoot the broken one?  It'd be great if the chips were in IC sockets so i could swap 'em and check.

hmm.
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