**help** korg poly 61

D

Darkone_Beats

Guest
Hey.. I just picked up a Korg Poly 61 today for free.. When i plugged it, plugged headphones into the board, it automaticly plays a continuos (deep saw) sound.. I can not seem to stop it.. The hold fuction is not one or anything like that.. I am lost.. Tried searchin the net for info about this problem.. Please help if anyone can.. Thanks!!
 
Sounds like there's a problem with the envelope generators or the VCAs (the oscillators are basically always "on", their output just controlled by the VCA & EGs). You could open it up and see if there's something loose (like the EG chips) and thus easily fixable, otherwise it might take some servicin' to fix. You can find the service manual here (pdf link), which'll probably help in locating said parts. I don't recommend fiddling around with the internals if you don't have any clue about what you're doing, but if something's just physically loosened, it might be easy enough do it yourself...
 
Thanks.. Im looking at that now.. Also it seems like since its in that "hold" sounding mode when I try to go up the scale on the keys they dont all seem to play.. But then when I change the parameters or patch, the keys that didnt work, now work.. Seems like that constant hold sound is making it do this.. Id really love to get this workin good though.. But as of right now I cant even play it..
 
Well, as I said - the DCO puts out sound constantly; that's how it works. The envelopes & amp just attenuate the DCO output so it sounds like it "starts" every time you hit a key. So it's not really a "hold mode", you're probably just hearing the DCO as it is w/o the EG/VCA interfering. Not that this helps directly, but should help you understand how it works.
 
I can not see the EG chips on that pdf you linked me to.

---------- Post added at 07:35 AM ---------- Previous post was at 07:20 AM ----------

ok nevermind i found them.. do you know how i would tell if the six EG chips are properly working or are lose or not ??
 
Poly 61

Yep Krushing is quite right you have a eg problem
The ssm2054 ics recieve a gate 5v on pin6 this is confirmed by an led lighting on the pcb. A good way of checking is stick it in hold mode play same note 6 times and see how many lights are lit on the board. Also tells you what one isn't working assuming you get any lights up at all. the Cvs come in from the digi board via the flat ribbon via four restiors i think "havn't actually got the 61 open to compare with the circuit"
funny enough i've just brought a dead one off ebay got it working but i've got the same issue I havn't had time to check it out yet but a quick look at the service manual revealled that much.
usually with Korgs the battery leaks all over the board, corrodes the tracks on the pcb travells up the connecters and wires from board to board if the battery has leaked chances are that some damage has occured it will need cleaning any corrored tracks or components replacing including whatever connectors and wiring is needed. I've actually got 2 of them the other was a buy dead of ebay too and was in far worst condition electronicly thats working fine now but does take a long time to tune that is a fault but I can't find the time to investigate that one just yet.
 
I got a synth tech here thats gonna fix mine.. any thoughts on the most I should spend on repair ? I got the Keyboard for free so..
 
Hi Darkone
Had another look at the circuit again haven't checked physicly but it looks as though the gate pulse is derived from the keyboard matrix this goes into IC9 or IC10 both are a 14175 this then comes out of the cpu board on connector CN12 and goes to pin 6 of each SSM2054 Eg generator IC 6 In total.As for repair costs Depends on what exactly is wrong A really good conditioned poly61m in full working order is worth on a good day about £200-£250 a non midi about £180-£220 maybe a tad more but not much. they're not that sort after but equally as good as say a Juno6 without the pricetag IMHO. allthough Juno owners will argue I've owned Juno's Sh101s Dx7's Pro1's the Pro1 was good but the others really were not much to write home about and no way worth the money people ask for them on ebay! So if yours is in good condition £100 would not be unreasonable amount to spend but bear in mind that whilst the Cmos 14000 and 4000 series IC's are a few pence each maybe £1-2 if you get them off ebay the SSMs are obsolete and can cost anything up to£30-£40 each 6 of those is more than the thing is worth hence a lot of these get stripped for the expensive SSMs in them. Then your man will want between £30-£70 for the hour or two it'll take too fix it unless he's a mate then a good drink might do it?
I got the second one for spares but as it can be fixed i'll restore it and moddify the other one I have, with knobs for direct paremeter control over the filter vca egs and waveform selection you lose the presets but its far more tweakable look up modified poly61 on youtube!
Good Luck
 
ya he was thinking around 200$ to fix it from what I was telling him over the phone.. Hes not a friend of mine or anything so.. Do you think that is worth it ?
And if I do the mod do you loose all the sounds ? and can you save new sounds you design ??
 
Actually he doesn't know whats wrong yet thats why he's getting a tech to look at it.

As the man says it depends on what it is worth to you?

There are lots of under rated digi modules "Like the Novation A station" that will do a good job for about the cost of repairing the Poly61.
I checked out the SSM2054s theres a place in the states want about $40 each fir them. The MC14175s are about $15 but shopping around should be less.

I'm in the UK so $200 is what £140 ? asuming thats US bucks. As I said a good working one in the UK will cost about £200 so if you paid nothing you'll still be quids or bucks in if he does a repair and a service for $200. As for the mods if those are done there is no way to save patches same as a juno6 but you'll have direct access so in reallity you could tweek sounds in seconds. If you were able to scan all the pots and switches you could save like a juno60 does but it ain't worth it on this machine.

I've just pulled the digi board on mine and it is really contaminated with battery leakage even though i've cleaned it it will need something like MEK to kill off the acid attack. It has spread through the connectors and wiring leaving a green residue behind this is also on some components too I will have to try and clean it off as some of the parts are obsolete and therefore very expensive if available at all.

Most Korgs of this age including the more sort after Polysix suffer with the battery leaking most of the problems are as a result of this, usually more a case of signals not getting there because of rotted tracks component legs rather than failed components but as I say this stuff is conductive so if it shorts out in the wrong place failed compnents will also occur.

Just to clarify there is nothing wrong with the DCO as you are getting sound.
There is an assigner or MUX system that routes to each voice in turn as you press keys Gate and trigger signals are routed to the EGs these are programed by control voltages in this case from a processer rather than a Pot. This then makes the SSM2054s produce an envelope to activate the filters and VCA this then allows the waveform from the OSC to pass through to the output. when the envelope closes it shuts down the VCF and VCA and stops the signal.
As the poly 61 has 6 voices and you get one voice hanging that changes every 6th note you have one Eg not working this is caused by either the SSM2054 not working for that channel, or not recieving the gate signal this can be checked at IC9 and IC10 it then goes to pin 2,4,6,8,10,12 of CN12 then wired to Analog board. If you play 6 notes in hold mode with the lid off you will see small LEDs lighting on the Analog board ( one on the right) you will see one not lighting. if you swap two of the chips over a different light will not light that will be the SSM failed if the light is the same one you will need to check IC9and 10 if the gate signal is not there you'll need a couple of MC14175's if it is you'll need some fine wire to repair the rotten tracks.

Another alternative is to get a few antistatic bags pull the SSMs put them in the bags and sell e'm on ebay and Get a Novation for what you get for them.
then sell the rest off on ebay as parts and use the proceeds to buy some needed bit for the studio?
 
Hi P Casso Play nicely Magneto
Wasn't meaning to offend but he had just posted i'm going to see a tech he thinks about $200 to repair and was asking if I thought that was a reasonable price? Bit like saying " What do the Slidey things do on my desk?"
I also thought that it was established that nothing was up with the DCO which incidently on a Poly61 OSC1 is a VCO under digital control and DCO2 is a pure DCO that is why it sounds bad on its own. "Made up from Square waves so the saw looks more like a staircase"
The term Hybrid that gets labeled to Juno6's and poly61's is wrong A hybrid is a DCO with Analog VCF and VCA juno's and Korg poly61's are Analog. or at least in the way the waveforms are produced. The digital part only deals with pitch and timing, negating the need for the antilog amp that is the down fall of all analog synths. Try keeping an early RA minimoog in tune. DCO's are things like Casio CZ5000 . Then it gets complex you get DCO's that are wavetables like the PPG or Kawai K3 or you get DCO's that are sample players PCM romplers like everything else from the late 80's to the mid 90's D50 ,M1 SY77, K1, K2000
The more I think about it,between sticking my head into old kit like this and trying to find a good patch on a plugin wastes more writing and recording time than I care to imagine. Get a Supernova instead!

Anyway just to upset you I've fixed mine or it will be by this time tomorrow. My problem was caused by the battery corrosion eating the crimps at the bottom in CN12 line socket this caused the tabs to fall off so they were not contacting the pins of CN12 when I reconnected the digi board earlier I suddenly had lost 2 voices. A little wiggle of the wires got the voices to respond i'll change the connector and the crimps tomorrow. I'll use 2x 6way molex as i have those already. instead of the 12way and the most likely obsolete crimps. So as I said this stuff wicks up the wires buggers the connectors and the tracks on the board rots the legs off components. I had to chuck a Akai S1100 year or two ago wasn't battery that time it was conductive salts "comes off the fingers of the people who made them" was stored in a damp room "good for salt growing" the board had hardly any undamaged tracks left on the main board and some of the components legs got eaten away tried to fix it, managed to get it to light up and do some wierd stuff on the display but other thanthat got nowhere with it. Took up too much of my time so I donated it to a mates studio as a rack blank.

Proff Xavier
 
Lamster said:
Hi P Casso Play nicely Magneto
Click to expand...

Fair enough

magneto_15266.jpg
 
Ho HO HO Nice!
Anyway Darkone
My Poly61 is now working all I need to do is put a new battery in it and load the Factory Presets " Downloadable as a wav file" play it from my laptop into the tape in socket and bingo! Now about yours if its a problem is like mine I recon I spent about 4hrs on mine but I completely stripped, cleaned and rebuilt the keyboard as this thing was in a bad way. I cleaned and repaired the digi board and had to clean the flat foil cable and remake one end of a loom at CN12 12crimps. 2hrs of that was removing the keyboard taking all the keys out all the rubber contacts out cleaning the pcb the contacts and giving the keys a bath and putting it all back together again. the loom took 1/2hr and the digi board 1hr or so to clean and 1/2hr to repair if its only the loom and battery damage you'll be looking at about 1-2hrs labour plus $10-15 for parts don't know what your tech charges but my "mates rate" is 0-£10 P/h if I don't like you or your not a mate its £25-£30 that about $45-50 so in answer to your question about $200 being fair? It is if its as bad as mine was, but if its say just the loom corroded at the plugs then$75 should well cover it

---------- Post added 03-01-2012 at 09:54 PM ---------- Previous post was 02-23-2012 at 12:06 AM ----------

Just reading my post and realised I made an error. If the SSM2054 is dead the Led will still light.
As that recieves the gate pulse from the digi board It was late when i wrote it

---------- Post added 03-27-2012 at 09:59 PM ---------- Previous post was 03-01-2012 at 09:54 PM ----------

Also thought I'd add this as reading back I have given duff info.
The Cvs for DCO1 come from the Antilog board or on the analog board on the later version the signals are generated for this from 2 of the 8253's on the digi board sent to the antilog then multiplexed through the 14051 on the analog board. I was looking at DCO2 the signals are generated on the other two 8253's then sent via the flat cable to the analog board through 4 resistors one for 2,4,8,16 footages The poly 61 selects one line but if you added switches here you could make the thing like a sort of addertive osc as you could select each footage on/off separately.
Sorry about being a P***T and giving duff info.

---------- Post added 04-23-2012 at 09:44 PM ---------- Previous post was 03-27-2012 at 09:59 PM ----------

Hi Darkone_Beats

Did you get the Poly61 Fixed in the end?

And what was the Problem?

And out of interest for anybody else here:
The other P61 I had that would not tune up for 1/2 hour was a power supply fault making the 15V line about 0.25V under the lowest level allowed in the spec!
 
Hi everybody,
I just read your posts while trying to repair failure of voices 5+6 on my p61 after battery leakage. SSM chips are fine (as tested by flipping them around), all 6 LEDs light up on the voice board upon sequential triggering, corresponding connectors from CN12 transmit +5V upon triggering. I am a rookie in this field, therefore i´d be glad for any additional suggestions what to test and what would you suspect to produce the error.
Thank you very much.
s97
 
selector97 said:
Hi everybody,
I just read your posts while trying to repair failure of voices 5+6 on my p61 after battery leakage. SSM chips are fine (as tested by flipping them around), all 6 LEDs light up on the voice board upon sequential triggering, corresponding connectors from CN12 transmit +5V upon triggering. I am a rookie in this field, therefore i´d be glad for any additional suggestions what to test and what would you suspect to produce the error.
Thank you very much.
s97
Click to expand...

Ok not got a drawing to hand but if I recall the Leds are indicating that the mux is selecting the voices on the analog board the SSM chips are filters one per voice.
I think the OSCs are controlled from the CPU board or at least the tuning and the swiching.
The Battery depending on how long its been leaking will cause varying amounts of damage.
Caught early it may have corroded tracks and the etch resist may flake off but essentially no broken tracks.
A worst case will be the the acid from the battery will travel round the board up wire and even onto other boards it will spread all the time there is a circuit for electrolosis to happen.
You will need to clean off and nutralise the acid with something like MEK watch out as this will melt plastic then after that wash the board off with IPA you can then look for damaged tracks.
As you have lost voices Its a good bet you have lost some tracks on the CPU board.
A couple of years ago my Cheetah MS6 did the same thing and the corrosion rotted the pins on a couple of chips which I had to change as well as repair tracks.
I had 2x Poly 61s sold 1 now but both had battery damage and both when I repaired them I fitted an off board battery.
With one I fitted a lithium type and used a diode in line and the other I fitted a NiMh with long wires going to the board
I'm affraid its a case of looking at the board for damage once you have repaired those track if it doesnt work then it'll be time to get the test gear out.
If you come back I will try to find a drawing.
You don't mention what flavour P61 you have there are basicly 3 types. Talking about only the boards on the base chassis the original has three boards (2 + little aux board) the 2nd model has only 2 boards
as does the 3rd version which is the Poly61m this has a factory fitted midi board in addition to the CPU and Analog board.

regards
 
You must log in or register to reply here.
Back
Top