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I have my dream synth - help me get it working!

I have my dream synth - help me get it working!

2014-02-19 by <moondog1311@gmail.com>

Hello good Polysix people,

After nearly 30 years of lusting after a P6, I finally took the plunge and bought a lucky dip from eBay. Good overall cosmetic condition, inside it had the usual battery corrosion issues; but the board has been mended (rather crudely) with a new lithium battery, and the CPU seems to be behaving and presets are remembered and recalled.

The keys were appalling, only a few worked. So I stripped 'er down and rubbed 'er good and proper with alcohol (no giggling please) and I now have a working keybed.

Which brings be to the issue at hand, only the 1st voice seems to be working. On poly mode you'll have to hit a key six times before it fires again. on Unison, it acts as a mono synth. Now the strange thing is when this was purchased last week at least 4 of the voices were working (it was hard to tell because of the unresponsive  keys and a irate seller).

All the internal LEDs fire in order when a key is pressed. I am really hoping that it's not the filter or envelope chips that have all gone. If so, how and why so quickly?

Anyone have any ideas?

I know it only has one voice, but it is truly sublime. I just need five more..

Respectfully,

Moondog


Re: [PolySix] I have my dream synth - help me get it working!

2014-02-20 by Bob Grieb

Hi,

    Others know the Polysix better than I, but here are some suggestions anyway:

  The first thing to do is download the service manual from the web and start getting
familiar with the circuit, and where the different test points are.

  Then I would measure the power supply voltages and make sure they are good.
Voltages that are too high can damage expensive chips.

   Assuming the voltages are good, I would look at the control signals that feed the voice
chips.   The gate signal turns on the LED, so it seems that one is working for all
six voices.  But there are other voltages that are separate for each voice.   Maybe they
are only getting to voice 0?   If you put the synth in unison mode, then I would expect
the control voltages for the VCA and the filter cutoff and pitch to be the same for all
voices.  If you turn up the sustain and put something on a key to hold it down,  then you can
measure the voltages and see if they are getting to all 6 voices.  You should be able to measure
some of the voltages with just a DMM as they won't be changing for a sustained note.

   Unless you have a power supply voltage that's too high, I wouldn't expect 3 of the voices
to fail in a few weeks.  Hopefully it's just one thing that has failed and is keeping them
from coming on.

    Hope that helps.

        Bob


From: "moondog1311@gmail.com" <moondog1311@gmail.com>
To: PolySix@yahoogroups.com
Sent: Wednesday, February 19, 2014 3:31 PM
Subject: [PolySix] I have my dream synth - help me get it working!

 
Hello good Polysix people,

After nearly 30 years of lusting after a P6, I finally took the plunge and bought a lucky dip from eBay. Good overall cosmetic condition, inside it had the usual battery corrosion issues; but the board has been mended (rather crudely) with a new lithium battery, and the CPU seems to be behaving and presets are remembered and recalled.

The keys were appalling, only a few worked. So I stripped 'er down and rubbed 'er good and proper with alcohol (no giggling please) and I now have a working keybed.

Which brings be to the issue at hand, only the 1st voice seems to be working. On poly mode you'll have to hit a key six times before it fires again. on Unison, it acts as a mono synth. Now the strange thing is when this was purchased last week at least 4 of the voices were working (it was hard to tell because of the unresponsive  keys and a irate seller).

All the internal LEDs fire in order when a key is pressed. I am really hoping that it's not the filter or envelope chips that have all gone. If so, how and why so quickly?

Anyone have any ideas?

I know it only has one voice, but it is truly sublime. I just need five more..

Respectfully,

Moondog




RE: I have my dream synth - help me get it working!

2014-02-20 by <moondog1311@gmail.com>

Thanks for your quick reply Bob, I knew this would be a friendly site.

OK, I've checked the PSU output voltages, all is as it should be. So are all the input voltages on all the SSM chips. Also checked the CV for the sustain input which varies correctly, again it's identical for each channel, as is the Cutoff CV.

I have discovered though, that in EG mode, only v0 sounds. In GATE mode, v0, 2, 3 and 5 now sound. v2, v3 and v5 are not as loud as v0 but hopefully this is just a trimmer setting. Do you know where this could be?

My knowledge of this is extremely thin, but I'm getting the terrible feeling that 5 Envelope chips have gone, plus 2 VCOs/VCFs

Anything else I need to be look for or some other ideas?

Thank you again,

Moon

[PolySix] RE: I have my dream synth - help me get it working!

2014-02-20 by Malte Rogacki

On thing you can test easily to see if the envelope chips are working:

Even in Gate mode the envelope controls the filter (if appropriately set).
So dial up a patch with filter envelope modulation and low Cutoff and
you'll see if an envelope is generated.

Do you have an oscilloscope? This would make things much easier.

Re: [PolySix] RE: I have my dream synth - help me get it working!

2014-02-20 by Bob Grieb

Hi,

Are the EG chips socketed? If so then you can use voice 0 as your
Known good channel for testing the other five EG chips. I am away from
Home so I cant check my P6.

Also you could check the other chips this way if they are in sockets.

Bob

From: moondog1311@gmail.com <moondog1311@gmail.com>;
To: <PolySix@yahoogroups.com>;
Subject: [PolySix] RE: I have my dream synth - help me get it working!
Sent: Thu, Feb 20, 2014 1:13:20 PM

 

Hi Malte,


Yes, I do have a scope - which points should I set it to?

Regards,

Bruno

[PolySix] RE: I have my dream synth - help me get it working!

2014-02-20 by Malte Rogacki

Do you have the service manual handy?

I'd probably put the Polysix in Unison mode, oscillator at sawtooth, no
subosc - and then play a note.

The filter input is at pin1 of the SSM2044; the signal there is pretty weak
- about 40mV or so. But in theory you should see a clear sawtooth there.

If you have a signal there you should check if it makes it through the
filter. Put Cutoff at max and all other filter setting to zero (which means
for EG Intensity center).
In theory you should now see a similar sawtooth at pin3 of the 2044. If not
then this hints at some problem within the filter. You could easily find
out if the filter IC is faulty by swapping it with one from a working
channel then.

For the envelope you might want to put all controls in the middle; then
measure the top side of R143 for each channel. In theory you should see the
voltage change from the envelope there (between 0 and about 5 volts).

Anyway, this should get you started, I hope.

RE: [PolySix] RE: I have my dream synth - help me get it working!

2014-02-20 by <moondog1311@gmail.com>

I'll get on with this now. Huge thanks for all the info.

Quick question, will it damage the Polysix to run it without a 2044 or 2056 in each channel? Much easier to take them all out and through a process of elimination discover which chips are dead and if anything else is amiss.




RE: [PolySix] RE: I have my dream synth - help me get it working!

2014-02-20 by Malte Rogacki

I've run a Polysix without SSM2044 in five channels before. I don't see why
this shouldn't be possible.

(I did this because the global CV scaling was completely off and it was
easier to measure the tuning for just a single voice - so removing the five
other 2044 and using the Polysix in Unison mode gave me a nice single-voice
synth.)

Re: [PolySix] RE: I have my dream synth - help me get it working!

2014-02-20 by Bob Grieb

I really doubt that you could damage anything that way.
The only possibility would be if the supply was not well regulated
and went higher with less load, damaging some other chips, but in this
case, that doesn't seem like a possibility.  Be careful not to bend any pins under
when you plug them into the sockets.   And pry evenly from both ends to remove them
from their sockets, to avoid bending any pins that way.  Also, since these chips are so
hard to replace, I would put them on conductive foam or some metal (or aluminum foil) to tie
all the pins together to avoid any chance of static damage.  Probably not possible
anyway, since these are probably bipolar and not MOS chips.

Another question is:   Could you possibly damage anything in a good channel by
installing a bad chip there?   I don't think you have to worry about that either.
In some other types of circuits this would be a real possibility.

   Bob


From: "moondog1311@gmail.com" <moondog1311@gmail.com>
To: PolySix@yahoogroups.com
Sent: Thursday, February 20, 2014 8:06 AM
Subject: RE: [PolySix] RE: I have my dream synth - help me get it working!

 
I'll get on with this now. Huge thanks for all the info.

Quick question, will it damage the Polysix to run it without a 2044 or 2056 in each channel? Much easier to take them all out and through a process of elimination discover which chips are dead and if anything else is amiss.






Re: [PolySix] RE: I have my dream synth - help me get it working!

2014-02-20 by Bob Grieb

Also, it seems if you install the SSM chips backwards and apply power,
you will fry them.  Easy to do...

  


From: "moondog1311@gmail.com" <moondog1311@gmail.com>
To: PolySix@yahoogroups.com
Sent: Thursday, February 20, 2014 8:06 AM
Subject: RE: [PolySix] RE: I have my dream synth - help me get it working!

 
I'll get on with this now. Huge thanks for all the info.

Quick question, will it damage the Polysix to run it without a 2044 or 2056 in each channel? Much easier to take them all out and through a process of elimination discover which chips are dead and if anything else is amiss.






Re: [PolySix] RE: I have my dream synth - help me get it working!

2014-02-20 by <moondog1311@gmail.com>

Hi Bob,

I have applied all the logic I know, and I have to accept its answer. I have five dead (or dying) 2044s and five dead (or stuck) 2056s. Luckily the good remaining VCF and EG SSMs work in all the V0-V5 channels, so at least the underlying circuits are good, if needing calibration. But what is the chance of so many dud ICs! My luck, I guess.

Shocked by the cost of the replacements, especially the EG. I have managed to source both for cheaper in China through Ali Express. 
Does anyone have any experience of far eastern chips? Anything I should beware of?

I have learned more in the past 12 hours about analog synths that I have in a lifetime. Thank you again for your kind support - This Polysix (del volante) will live again.

Moon

RE: I have my dream synth - help me get it working!

2014-02-22 by <josh.nursing@gmail.com>

Yes, they're certainly expensive, but it's because they are used in poly-analogue synths, have great sound and are also not manufactured anymore. The SSM2056 is of higher price than the SSM2044 because the latter are more available. I read somewhere that it was because Korg had ordered a lot of those once, but then designed their own filter chip (the NJM2069?).

Yash

Re: [PolySix] RE: I have my dream synth - help me get it working!

2014-02-22 by Dennis Matana

Korg developed the Korg 35 filter ic found in the MS10 etc...NJM = JRC = New Japan Radio...has nothing to do with Korg....

And i have been reading this topic and so you bought a P6 on ebay and now only one voice works? was it advertised like that? i would hold the seller responsible for the defective ic's....send it back to the seller and reclaim your money....5x SSM 2044 and 5x SSM2056...look at www.syntaur.com how much you need to invest to get it working again....

ps what did you pay for the P6? I'm about to sell mine
 
 
                           


On Saturday, February 22, 2014 1:11 AM, "josh.nursing@gmail.com" <josh.nursing@gmail.com> wrote:
 
Yes, they're certainly expensive, but it's because they are used in poly-analogue synths, have great sound and are also not manufactured anymore. The SSM2056 is of higher price than the SSM2044 because the latter are more available. I read somewhere that it was because Korg had ordered a lot of those once, but then designed their own filter chip (the NJM2069?).

Yash


Re: [PolySix] RE: I have my dream synth - help me get it working!

2014-02-22 by <josh.nursing@gmail.com>

Nobody said Korg manufactured the NJM2069. And I do know NJMs are manufactured by JRC.

Besides, the notion that NJM has nothing to do with Korg is bull: talking about just the NJM2069, which is a fantastic filter if you've tried the 'Moog Slayer' and FM mods on the Poly-800, it's in that synth, the Korg DW-6000, the DW-8000 and the DSS-1.

From :

"SSM2044 chips are easily found as many thousand were made for Korg but the large orders never materialized as Korg made their own chip the NJM2069 and then went digital with the M1."

Yash

Re: [PolySix] RE: I have my dream synth - help me get it working!

2014-02-24 by <moondog1311@gmail.com>

Well, it was a surreal experience to collect it. It was sold as just the keybed being defective, which it most certainly was. Whilst checking it out, discovered that it only managed to get 4 voices at most together, and the only on gate mode rather than envelope mode. When it was home I hooked it up to my scope and I could see that the faulty filters just didn't give the correct saw; kinda like the filter was half closed. And the EGs either were dead or just gated straight on/off. That's the good thing about having one channel that works, it's easy to see exactly what's broken. At least they are socketed!

However, it was cosmetically quite good so I took a gamble and parted with £275 for it. Even with the 10 replacement SSMs (which are hopefully winging their way from China for £120 total) I am still happy at that price. The battery has been replaced and the KLM-367 mended, but truth be told, it looks like a dog's dinner of a repair job. It's behaving itself at the moment, but I will probably swap for a Kiwi 6 at some point in the future.

I have concerns now that something has caused the loss of so many chips. My DMM shows that the PSU is outputting the +15v -15V +5v correctly. Will probably change (at least) the large caps on the PSU board in case they are not filtering spikes correctly. Just hope the voltage regulators are holding up. Will report more when I finally get my SSMs.

It feels good to be part of this exclusive club.

Moon

RE: [PolySix] RE: I have my dream synth - help me get it working!

2014-02-24 by tim p

Good work!

Where did you source the SSM chips from? Are they clones, NOS or pulled?

Cheers

Tim
From: moondog1311@gmail.com
Sent: ‎24/‎02/‎2014 15:33
To: PolySix@yahoogroups.com
Subject: Re: [PolySix] RE: I have my dream synth - help me get it working!

 

Well, it was a surreal experience to collect it. It was sold as just the keybed being defective, which it most certainly was. Whilst checking it out, discovered that it only managed to get 4 voices at most together, and the only on gate mode rather than envelope mode. When it was home I hooked it up to my scope and I could see that the faulty filters just didn't give the correct saw; kinda like the filter was half closed. And the EGs either were dead or just gated straight on/off. That's the good thing about having one channel that works, it's easy to see exactly what's broken. At least they are socketed!


However, it was cosmetically quite good so I took a gamble and parted with £275 for it. Even with the 10 replacement SSMs (which are hopefully winging their way from China for £120 total) I am still happy at that price. The battery has been replaced and the KLM-367 mended, but truth be told, it looks like a dog's dinner of a repair job. It's behaving itself at the moment, but I will probably swap for a Kiwi 6 at some point in the future.

I have concerns now that something has caused the loss of so many chips. My DMM shows that the PSU is outputting the +15v -15V +5v correctly. Will probably change (at least) the large caps on the PSU board in case they are not filtering spikes correctly. Just hope the voltage regulators are holding up. Will report more when I finally get my SSMs.

It feels good to be part of this exclusive club.

Moon

Re: [PolySix] RE: I have my dream synth - help me get it working!

2014-02-24 by Chromatest J. Pantsmaker

One possibility is that this polysix was used for parts, with the bad parts from other synths swapped into it.  This way it would *look* like a complete synth, and with the keyboard defective, it would be difficult to test.  If that were the case (no way to know), then the P6 didn't cause all those chips to go bad.

Just a thought...


On Mon, Feb 24, 2014 at 7:33 AM, <moondog1311@gmail.com> wrote:


Well, it was a surreal experience to collect it. It was sold as just the keybed being defective, which it most certainly was. Whilst checking it out, discovered that it only managed to get 4 voices at most together, and the only on gate mode rather than envelope mode. When it was home I hooked it up to my scope and I could see that the faulty filters just didn't give the correct saw; kinda like the filter was half closed. And the EGs either were dead or just gated straight on/off. That's the good thing about having one channel that works, it's easy to see exactly what's broken. At least they are socketed!

However, it was cosmetically quite good so I took a gamble and parted with £275 for it. Even with the 10 replacement SSMs (which are hopefully winging their way from China for £120 total) I am still happy at that price. The battery has been replaced and the KLM-367 mended, but truth be told, it looks like a dog's dinner of a repair job. It's behaving itself at the moment, but I will probably swap for a Kiwi 6 at some point in the future.

I have concerns now that something has caused the loss of so many chips. My DMM shows that the PSU is outputting the +15v -15V +5v correctly. Will probably change (at least) the large caps on the PSU board in case they are not filtering spikes correctly. Just hope the voltage regulators are holding up. Will report more when I finally get my SSMs.

It feels good to be part of this exclusive club.

Moon



Re: [PolySix] RE: I have my dream synth - help me get it working!

2014-02-25 by <moondog1311@gmail.com>

Looking at the seller, I initially thought it was a distinct possibility.

However, in this case it's unlikely. All the VCFs had the same batch number, as did the EGs. Something must have caused them to go, and accusatory finger first pointed to the PSU; but I don't think it is over-voltage. The voice board has a constant 10v as it should.

When the new ones arrive I'll test them carefully comparing them with the scope, before giving it a full calibration.

RE: [PolySix] RE: I have my dream synth - help me get it working!

2014-02-25 by <moondog1311@gmail.com>

NOS, or so I'm told. But this was from China, and words are cheap!
I had to go to two suppliers, as one had only 2 x SSM2056, but the full set of SSM2044. they were about $100 delivered in total. The next cheapest for the other 4 x SSM2056 were another $100, and so I ordered them as well.

All sourced from Alibaba - it's actually quite easy, with online chat to the various suppliers. Try to get them to use Ali Express, which is very much like the BIN part of eBay, with buyer protection and tracking etc.

I'll let you know if/when they arrive and the results after testing etc.

Re: [PolySix] RE: I have my dream synth - help me get it working!

2014-02-25 by Bob Grieb

Could there have been a power supply problem at one time, which was later
fixed?   I bought an Ensoniq ESQ-1 which had an extra wire added to the pcb.
Turns out someone was doing "circuit bending" on it, and had connected the
+5 and +12 supplies together.    Luckily nothing was damaged.  I had to
troubleshoot to find that problem.   Just was totally not expecting something
like that.

    Bob


From: "moondog1311@gmail.com" <moondog1311@gmail.com>
To: PolySix@yahoogroups.com
Sent: Tuesday, February 25, 2014 3:54 AM
Subject: Re: [PolySix] RE: I have my dream synth - help me get it working!

 
Looking at the seller, I initially thought it was a distinct possibility.

However, in this case it's unlikely. All the VCFs had the same batch number, as did the EGs. Something must have caused them to go, and accusatory finger first pointed to the PSU; but I don't think it is over-voltage. The voice board has a constant 10v as it should.

When the new ones arrive I'll test them carefully comparing them with the scope, before giving it a full calibration.