Yamaha CS40M - any users here?

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Yamaha CS40M - any users here?

Postby radek tymecki » Thu Jul 02, 2009 3:01 pm

I'm tryin to fix CS40M... Somebody just totally desoldered everything, cut wires etc. Yammy looked like... hmmm do it yourself thing haha

Anyway i still have problem.

1. big mod board - what should be connected to CT? I can see 2 pins there but no cable at all,
2. inder bender board there is 1 green, 2 black, 2 orange and 1 orange and red cables

probably i'll need Your help

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Re: Yamaha CS40M - any users here?

Postby nathanscribe » Thu Jul 02, 2009 8:36 pm

I've got a CS-40M and the full service manual - I'll have a look tonight and see what i can find.

Good luck.

PS, looking at your pics the compartment for the memory back-up battery is missing. It should fit into that hole in the base. At least a couple of those wires will go there. I'll check these connection for you asap.

PPS, I'm guessing the thick green one is earth. Don't quote me. I'll check.
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Re: Yamaha CS40M - any users here?

Postby nathanscribe » Thu Jul 02, 2009 10:15 pm

OK: CT on the MOD board carries power. CT pin 1 (left, as you look from above) is + (plus) 5V. CT pin 2(right) is - (minus) 10V. It's unconnected on mine too. It's a test point.

The thick green wire is earth.

The thicker, taped-up pair of black/orange goes to the battery compartment. Black is ground, Orange is positive. I'll check my files later to find out what kind of batteries you need. They look to be AA-size, probably around 1.4V each, two of. The outer case of the battery compartment should also have a tab for connecting an earth lead (the thick green one)

It looks like you're missing the headphone jack. Taking the thin pair of wires, Orange is tip, Red is ring; presumably the large green earth cable was also providing ground for the socket.

Lastly, the thin orange/black pair with the 2-pin connector: in the whole service manual, I can see only one mention of it - it's labelled "BC". But it's not connected to anything in my CS, and there's no sight of it in the schematics.

Hope that helps.
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Re: Yamaha CS40M - any users here?

Postby radek tymecki » Fri Jul 03, 2009 10:10 am

ok :) i've tested this CT 2pin connector and it has +5V and -10V, found phonejack :)

anyway cs40m seems to be crazy. most of controls don't work.

ps. lfo chip is broken
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Re: Yamaha CS40M - any users here?

Postby madtheory » Fri Jul 03, 2009 10:50 am

Well, the previous owner should be shot... That's a very reliable synth, but those CMOS chips are a problem to replace. Have you checked out old crow's CS-80 site? Lot of info there that would be relevant.
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Re: Yamaha CS40M - any users here?

Postby nathanscribe » Fri Jul 03, 2009 11:16 am

You seem to have a floating connector at the top right if your first photo. Something you'd missed?

The 40M is crazy when it works, too...
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Re: Yamaha CS40M - any users here?

Postby radek tymecki » Fri Jul 03, 2009 11:19 am

So... Should I try to replace all 4xxx IC's?
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Re: Yamaha CS40M - any users here?

Postby madtheory » Fri Jul 03, 2009 4:36 pm

No, don't try to replace them all... just the ones that are broken... diagnosis is your friend :)
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