[sdiy] Cheetah MS800 replacing NiCd Varta Mempac

Peter Pearson electrocontinuo at gmail.com
Fri Jun 4 18:11:37 CEST 2021


Personally, I'd replace that resistor with a diode like the popular fix on
the Polysix CPU board and install a non-rechargeable battery with solder
tabs like the BR2/3 or TL4902 (whichever fits nicer).  One of those might
even have a holder you could fit if you look around.  It will last
decades.  Looks like you can also back up the patches via sysex so just do
that at some point before the battery dies if it's important to you.

While you're in there, maybe back up the EPROM if there is one (can't find
a schematic) and send it to this site:

https://dbwbp.com/index.php/9-misc/37-synth-eprom-dumps

It would be good karma.

On Fri, Jun 4, 2021 at 11:59 AM Richie Burnett <rburnett at richieburnett.co.uk>
wrote:

> Thanks.  Sadly no luck now though.  NiCd seems to be outlawed in most
> places
> now :-(
>
> -Richie,
>
>
>
> -----Original Message-----
> From: Joel B
> Sent: Thursday, June 3, 2021 4:51 PM
> To: Mike Bryant
> Cc: Richie Burnett ; synth-diy mailing list
> Subject: Re: [sdiy] Cheetah MS800 replacing NiCd Varta Mempac
>
>
> Not sure if still possible but I was able to find a company selling
> replacement nicads that looked like they matched the spec of my cheetah
> MS6
> back in 2016… didn’t want to remove the charging system:
>
> This is from my receipt:
>
> 3.6V 110MAH NICD
> Item# NIC0010
> https://interstatebatteries.com/
>
>
> Worked for me.
>
> Joel
>
> Sent from my iPhone
>
> On Jun 3, 2021, at 8:10 AM, Mike Bryant <mbryant at futurehorizons.com>
> wrote:
>
>
>
> I've always dropped in NiMH into NiCad slots okay.  But that's no
> guarantee.  As you say not getting rid of the old one is a far worse
> scenario.
>
> -----Original Message-----
> From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of
> Richie
> Burnett
> Sent: 03 June 2021 15:30
> To: synth-diy mailing list
> Subject: [sdiy] Cheetah MS800 replacing NiCd Varta Mempac
>
> Hi all,
>
> I'm currently servicing a Cheetah MS800 digital wavetable synth and want
> to
> change the old NiCd Varta Mempac to a brand new NiMH Varta Mempac before
> putting it up for sale.
>
> The old blue NiCd battery hasn't started to leak yet, and is still holding
> it's charge but I know that old NiCd Mempacs are regarded as a ticking
> time-bomb in equipment of this age (>.<)  I wouldn't feel comfortable
> selling it without addressing this issue first.
>
> The existing 100mA 3.6V NiCd trickle charges from the 5V supply rail
> through
> a 1k resistor when the unit is powered up.  Should I be looking at
> changing
> this trickle charge current when changing the battery type to the 150mA
> 3.6V
> NiMH replacement?
>
> I did a search online and found very little solid information about this.
> Everything from "The NiMH Mempacs are a drop in replacement" to "you need
> to
> decrease the trickle charge current because NiMH is less tolerant of being
> overcharged"  The trickle charge current already seems low to me.
>
> I would be interested to hear your thoughts!
>
> -Richie,
>
>
> --
> This email has been checked for viruses by AVG.
> https://www.avg.com
>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace at synth-diy.org
>
>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace at synth-diy.org
>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace at synth-diy.org
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20210604/a01a598b/attachment.htm>


More information about the Synth-diy mailing list