Looking for a YM1037 in UK

[der Warst]

So I started working on my Yamaha CS01 again. It's my only analog synth and I love it to bits. I've done a few mods and added a highly liquid interface to it a few years ago and since I'm in a building frenzy at the moment, I opened it up again to see what else can be done. I found that one article in someone's blog where he made noise and VCO output available as modulation sources. Sweet.

But with poking around to make it work, I must have fckd the LFO. It's just not there any more. I've checked the signal path and there's just a few caps and resistors there. Nothing really that can break. 
The LFO is on the tone gernerator chip, which is a YM1037. I guess I must have overloaded and thereby fried the output somehow.
Needless to say that it's obsolete now. All my searches came up with dubious chinese wholesale sites... 
Does any one of you have any idea where I could get one or two of those for an affordable price?

Thanks for any help,
der Warst

[Remork]

ouch.. what exactly did you change? pix?
link to that mod?

if the tone generator still works, i doubt you fried the whole chip.
first, make sure it's really dead - 100% sure.

for those of you that read schems: service manual heaven..
only schem i could find easily, but it's got YM1050.
so not sure what pin you LFO output is on.

still, there should only be a single elco in between the chip and the pot, so checking on the pot is your safest bet:
one side goes to ground, middle is to the VCO/VCF switch, other side should be full LFO signal.

LFO at the fastest rate is only 28Hz, so unless you have a subwoofer you won't be able to listen in, best to check visually.
do you have a scope, or one you could use? for signals like these, even a software scope would do.
worst case you could use a multimeter and check AC voltage with the speed cranked. should be around 200mV.

[der Warst]

Yeah, I know the Schematic. I think YM1050 is the older one which didn't have the noise source included. The discrete noise generator is on the schematic but unpopulated on my circuit board.

On the pot is exactly where I tested. I've modded the LFO to go faster than usually, so it actually goes nearly audible.

I listened to it again and apparently, the LFO still seems to be there, it's just a lot weaker than it used to be...
Hm. Don't exactly know what to make out of this...

The mods I wanted to build in are here:
http://rga24.blogspot.com/2010/06/yamaha-cs01.html

[Gordonjcp]

I don't think you're going to be able to find a replacement for it.  It was probably a very custom Yamaha chip, and it's really unlikely that anyone has NOS parts or even good used pulls.

The good news is that you can probably make up a simple LFO circuit with an opamp and graft that in somewhere to replace it.  If you look here:
http://www.milton.arachsys.com/nj71/index.php?menu=2&submenu=4&subsubmenu=1

You'll see where Neil has done something similar for the chip in a Jen SX1000.

[der Warst]

So I listened to it again and compared it to some Youtube videos so I can hear the difference. The LFO is still there, only now it has only very little impact on the filter. I also realised that with an earlier modification, I had the 8k2 resistor removed to increase its impact. This worked alright with only the modwheel connected, but must have been too much once I sent it through the breath control pots as well.
My guess is that with my poking around I fried some amp inside the main chip. Bummer.

Guess I'll have to build a LFO then. I kinda wanted to avoid that, but then again I might use it as an opportunity to get a few more waveforms.
This one, for example, looks nice and simple:
http://www.analog-synth.de/synths/mod2/lfo_sh/lfo_sh.htm

It even uses a 1M pot, which would be handy because the speed fader is 1M. Might be worth a try...
Do you guys have any idea how I can make this work with the cs01 running on -9V and all? It seems to usually work on dual supply. would it still work if I connect the 084's vcc+ to GND and vcc- to -9V?
Do you think I'd have to buffer the signal? And if so, with what?

This thread is getting a bit out of context here...
So If a moderator wants to put it somewhere else, please do so.

[Remork]

is it the same for VCO modulation?

apart from the fact that an extra LFO would be funky -
if the original LFO is still there but just a little, then your guess you fried the main chip is just that - a guess.
it could just as easily be a busted elco. or the VCF chip.
really, try to get hold of a scope.

on a sidenote, that other LFO will probably work with the supply hooked up like you suggested, but the ground for the LFO will be at -4.5v.
it might work if you use a big coupling cap on the outputs to block that dc value, though.