korg poly 61m battery replacement anybody done this?

[selfpreservation]

has anyone any experience of modding the p61m with a lithium cell ?, i can find a guide for the poly six that says you need to remove a capacator and a resistor (i asssume the capacitor has something to do with the charging), but no guides for the poly 61 , i also found a battery replacement kit in the states which uses a solder type lithium cell (which im not keen on id rather use a battery holder) for the p61 which also states that you have to remove two components on the board doesnt tell which one though

from comparing the poly six battery replacement guide  here http://www.oldcrows.net/~oldcrow/synth/korg/polysix/battfix/klm367_markedmap_sm.jpg you remove r91 and c40
with the poly 61 schematic here
http://fa.utfs.org/diy/korgpoly61/Korg_Poly-61_ServiceManual.pdf
i think i need to remove r70 and c29(or poss c37) any ideas?

from what i have read you have to install the lithium cell with a diode (germanium or shottky)on the +ve rail to stop the charging circuit trying to charge the battery when the powers on , if so why is it necessary to locate and remove the two components ?

also can i just use a nimh directly instead of the ni-cad and will the p61 charge it
thanks for your help

[gmeredith]

If you use a NIMH battery and not use the keyboard for a while it will lose its charge fairly quickly. NiMH batteries don't seem to retain their voltage very well even when not used. So in a months time of not using the keyboard you may find all your presets missing.

Cheers, Graham

[selfpreservation]

thanks graham i wont bother with the nimh then

[Circuitbenders]

i have a vague memory that one of my poly61m's has a lithium cell battery in it, although i do have three and i have no idea which one it is, if it wasn't a dream i had. i'm not overly keen on the idea of opening them all up to find out.

Pick a number from 1 to 3 

[selfpreservation]

its gonna have to be 3 mate, what are you doing with 3 of them ? are they all alive ?im guessing no, ive got a dead p61 in a cupboard for spares its a necessity i love sound of the p61m but its a pain in the ass
have you ever thought about a way of turning the primary oscillator off and just having the 4bit digital nonsense or better still a mix knob ? ive also tryed  to add switches and 10k pots to isolate the dco/vcf amount from the joystick onto pots but i couldnt get it to work for some reason, the joystick has a 4 lug 10k pot with centre off , it only has one wiper , it looks liike the wiper tracks are on lugs 1 and 4 so i hooked up 10k pots with 1 to the wiper and 2 to pin 1 and the other 10k pot with 4 to the wiper and 3 to pin one  but it didnt work as expected it definatley did something but ot was hard to decipher exactly what with all the other niose and chaos ah well back to the drawing board then

[Circuitbenders]

I'll open up number 3 when i get a chance. 

I did look at some mods from the 61m a while back that i never actually installed and it looks pretty easy. As its analogue envelopes and filter under digital control, at some point between the digital section and the analogue section you're going to find the control voltages that set the analogue parameters. If you cut those traces and then find another 5V source (assuming its 5v CV's), then you can probably wire in a pot for some extra knobage. I was planning on having a switch for each parameter to select between the CV generated by the digital section by selecting the stored sound, and knob control.

[selfpreservation]

CHEERS

[Gordonjcp]

NiMH is a drop-in replacement for NiCad.  It *shouldn't* self-discharge in a month.  My Polysix has probably not been on for over a year, but still has its patches.  I replaced its leaky NiCad with a NiMH a couple of years ago, and it's been fine ever since.

Incidentally I've done exactly the same replacement (same NiCads replaced with the same NiMHs from the same supplier) on the site control boards for four of the five radio sites I maintain.   No problems with them, and it's cleared up a couple of annoying wee intermttent crashes caused by the failing battery spiking the memory supply line.

[selfpreservation]

right i have removed r70 ,a 470ohm resistor and replaced it for a schottky diode and it seems to be working ie storing patches and the current is only flowing in one direction

could anyone who knows about circuit design please  have a quick look at this http://fa.utfs.org/diy/korgpoly61/Korg_Poly-61_ServiceManual.pdf
page 12 , in the centre of the board you will see the battery circuit r70 is on the left, although you cant see it here r70 is connected tot the positive side of the battery
there is a capacitor c39 just below the +ve contacts for the battery c39 goes back to earth
my question is
A does it look like i have removed the correct resistor ie the charging resistor for charging the origiinal nicad  battery
B what is the purpose of c39 , is it just to smooth the power to the battery ? in which case does it need to be removed also

any help will be greatly appreciated

cheers ciaran

[gmeredith]

Gordon, are those NimH batteries you speak of connected to a charging circuit in the device? If they are, then, they will always have a decent charge. But if you have the gear switched off for a few months ie. in storage, where they aren't being charged constantly, they might not hold their charge very long while dormant. This has always been my experience with my NiMH batteries. There is a new generation of NiMH batteries on the market now that claims to hold 80% of its charge after 6 months, because of this issue.

cheers, graham

[Gordonjcp]

Yes, they are charged in the device.  They're charged through the same circuit that would have charged the NiCad battery.

The last time I fired it up (about three months ago) the Polysix still had all its patches.  Prior to that, I hadn't run it for over a year, and even then only for about half an hour.

[Ricoche]

Hello everyone,

I recently in Japan picked up a Korg Poly-61 in excellent condition with everything working on the synth.  I opened up to check on the battery and it was fully intact and in great shape. ( Varta 3.6v NiCad)  I am worried about potential leaking with this battery and would like to replace it as soon as possible.

I see a couple of people have replaced their battery with a NimH battery.  I am not sure which exact NimH battery everyone is using as a replacement.  If possible, it would be great if someone could direct me to a website where I might be able to order a NimH battery online or at least get a visual on what battery we're all talking about as a replacement.

I also heard this site here:  http://www.mik-music.org/tiki-index.php?page=Korg%20Poly-61%20Repair&pagenum=1 is a good place for info, but it's been offline for some time.

Thank you very much in advance for any info.

Jim

[Gordonjcp]

Any 3.6V NiMH battery.  They're a drop-in replacement for NiCad so just get one that looks about the same and fit it.

[Ricoche]

Thanks Gordon.  I'm curious, what mAh do you recommend for a 3.6v NiMH?  Does it matter?

Seems like most NiMH batteries I find on the internet are phone battery replacements.

Thanks!

Jim

[ElSmurf]

It took me a while to find a good description of the procedure of installing a lithium cell battery in the Poly61. As this thread pops up on the first page of google when searching for 'battery replacement' I thought I post my findings here :

According to Korg service bulletin for poly-61.
1) remove R70(470 ohm)
2)Remove transistor Q10
3)Replace nicad with lithium battery in same location
4)solder one 1N914 diode(or equiv) at location R70 and and another between Emitter and collector of Q10( cathode to C and anode to E)
5) if the CPU board is KLM475, change R146 to 2.2k ohm. If Cpu board KLM506 disregard R146

The diode at position R70 by the way, mounts on the PCB with its anode pointed towards Q10, cathode pointed towards(not connected) the positive end of battery.

Where I found this : https://jimatwood.wordpress.com/2011/03/27/korg-poly-61-synthesizer-sounds-great/