Polysix Rebuild

[Dan LB]

........it looks like the SSM2044.

There’s somebody local to me selling two of these chips. He wants €45 each for them. If you get stuck and can’t find them in the US I’d be happy to pick one up for you and post it.

[nickle15]

........it looks like the SSM2044.

There’s somebody local to me selling two of these chips. He wants €45 each for them. If you get stuck and can’t find them in the US I’d be happy to pick one up for you and post it.

Awesome offer and I'll let you know - thanks so much!!

[nickle15]

At long last we were able to lay out all the parts. Here's what we know we're missing:

1 voice chip
Microcontroller
1 7 pin wiring harness
Pitch/mod wheel assembly
Wooden chassis case
All the knobs
One button

Dad started his work on the transformer and planned to work from board to board just trying to get a sense of what might need to be fixed. He didn't get very far - the transformer is bad. So that's where we stand as of this morning. I'm going to get started on pricing the replacement parts we need, starting with the transformer.

[Folderol]

Best of luck with this.
I suggest you check on availability of the processor and the voice chip before spending too much.

[nickle15]

Best of luck with this.
I suggest you check on availability of the processor and the voice chip before spending too much.

Thanks!

Yes I plan to compile a list to see how much it will cost to get the known issues fixed. It's very possible that the cost of the parts would outweigh just buying a functional keyboard.

[jjlonbass]

Which microcontroller is missing? There are 2 - one, a 8049, is the "key assigner" and the other, a 8048, is the "programmer".
Both are mask programmed i.e. the software is hard-wired into the chip - there is no separate PROM. This means that you need the exact correct 8049 or 8048 part containing the correct software. Any old 8049 or 8048 won't work.
I suspect that these will be very difficult to find.

John

[nickle15]

Which microcontroller is missing? There are 2 - one, a 8049, is the "key assigner" and the other, a 8048, is the "programmer".
Both are mask programmed i.e. the software is hard-wired into the chip - there is no separate PROM. This means that you need the exact correct 8049 or 8048 part containing the correct software. Any old 8049 or 8048 won't work.
I suspect that these will be very difficult to find.

John

It's the 8049 that's missing. I was suspicious of how easy it was to find one - but now I know why. Again - your advice/direction is very helpful!

[rockydennis]

It's the 8049 that's missing. I was suspicious of how easy it was to find one - but now I know why. Again - your advice/direction is very helpful!

Taking a quick look online, I do see one site selling the 8049 for the Polysix for 30 Euros.

Here's a site with firmware code for various synths available for free, including the Polysix. I'm guessing the 8748 and 8749 which have eprom and are programmable, and are from the same family can be substituted for the 8048 and 8049 but don't quote me on that.
https://dbwbp.com/index.php/9-misc/37-synth-eprom-dumps

Here's someone replacing the 8049 for the Polysix with Arduino with the code made available.
http://synthhacker.blogspot.com/2013/03/polysix-replacing-8049-key-assigner.html

[nickle15]

It's the 8049 that's missing. I was suspicious of how easy it was to find one - but now I know why. Again - your advice/direction is very helpful!

Taking a quick look online, I do see one site selling the 8049 for the Polysix for 30 Euros.

Here's a site with firmware code for various synths available for free, including the Polysix. I'm guessing the 8748 and 8749 which have eprom and are programmable, and are from the same family can be substituted for the 8048 and 8049 but don't quote me on that.
https://dbwbp.com/index.php/9-misc/37-synth-eprom-dumps

Here's someone replacing the 8049 for the Polysix with Arduino with the code made available.
http://synthhacker.blogspot.com/2013/03/polysix-replacing-8049-key-assigner.html

Excellent - thanks for adding this guidance!

[Drew Stephenson]

The level of expert knowledge that is freely given on this site never ceases to amaze me.

[nickle15]

The level of expert knowledge that is freely given on this site never ceases to amaze me.

Amen!

[rockydennis]

Maybe replacing the 8049 with Arduino is the way to go -
"As many of you know, I made some pretty substantial modifications to my Korg Polysix. One of the biggest changes was to replace the keybed to enable aftertouch. To make this happen, I had to replace the Polysix's Key Assigner with an Arduino. It was a lot of work, but once I made the core hardware modifications, I found that I was able to add lots of features to the Polysix, such as: aftertouch and portamento, more interesting detuning for unison mode, a poly-unison mode, a Moog-like single-trigger mode, and a sustain pedal. All of these modifications were effected through software changes on the Arduino."
http://synthhacker.blogspot.com/2014/03/polysix-sharing-my-arduino-code.html

[BJG145]

That's hardcore. Respect.

[Folderol]

I'd like to know how the guy got hold of a Fatar poly aftertouch keybed.
Oh, and did he have to remortgage the house.

[The Elf]

I'd like to know how the guy got hold of a Fatar poly aftertouch keybed.
Oh, and did he have to remortgage the house.

I've often been told that they don't do one!

[Hugh Robjohns]

They certainly don't have one listed in their current line up.

They make plenty of keybeds with monophonic (channel) aftertouch, though -- and that's what the Arduino guy used to provide channel aftertouch in his Polysix, basically replicating the mod wheel functions from the keyboard pressure.

[Folderol]

I pretty much thought that was the case, but had half a hope I might have been looking in the wrong place.

[BJG145]

How's the jigsaw? I found one of these; untested, but can pop it in an envelope if you want to try it.

[nickle15]

How's the jigsaw? I found one of these; untested, but can pop it in an envelope if you want to try it.

That's very generous of you! Right now we're still stuck looking for a transformer. Not much else we can do until we solve that.

I would be very happy to try out the chip but would also like to pay you a fair price for it. Also, I'm in the US (not sure where you're at) so shipping might be an adventure!

PM is welcome if you want to continue the conversation. Thanks for checking in!

[ajay_m]

Assuming this is a standard linear power supply with a normal E-I laminated core transformer then there are plenty of options. You need to know the secondary voltage or voltages and the VA rating eg 50VA or whatever and then you can probably get an off the shelf replacement. Quite a lot of transformer manufacturers can also make custom voltages. Another option is to find an external PSU with the right DC voltage and just wire that in instead. Since you're rebuilding the case anyway it doesn't much matter if you do that instead.

[BJG145]

Right now we're still stuck looking for a transformer. Not much else we can do until we solve that.

There's one on eBay currently; they might accept an offer.

[jjlonbass]

If you can't find an original transformer, my best guess from looking at the service manual would be that one with 15V-0-15V secondary rated at 30VA or above should do the job; 50VA would be better if it will fit. This is based on the fact that the stated mains power consumption is 25W and that the highest voltage regulated DC rails at the output of the power supply are +15V and -15V. The unregulated outputs from the bridge rectifier and smoothing capacitors will be around +21V and -21V in this case.

You'll need to perform the power supply voltage adjustment procedures after replacing the transformer - I'd recommend doing this even if you fit an original replacement.

Using an external DC supply to replace the missing transformer won't be feasible.

John

[nickle15]

Right now we're still stuck looking for a transformer. Not much else we can do until we solve that.

There's one on eBay currently; they might accept an offer.

Thanks - I tried a couple of weeks ago but they rejected what I was willing to pay.

[ajay_m]

Looks very much like a standard 15-0-15 VAC transformer (sometimes referred to as 30V CT) and it is probably 30VA or so and the full power supply schematic and service manual appears to be at the link below. The fuses are rated 1A so that would confirm that a 30VA unit ought to be about right. The original transformer may have had 115V and 230V primary windings but you do not require them both, obviously, you just want a unit suitable for whatever your mains voltage is (sorry, not sure if you are in the US or not).

http://www.oldcrows.net/~oldcrow/synth/ ... iserv.html

A transformer that size ought to cost about £20 or thereabouts and is a stock voltage.