[sdiy] Cheetah MS800 replacing NiCd Varta Mempac

Michael E Caloroso mec.forumreader at gmail.com
Fri Jun 4 06:20:50 CEST 2021

In my own gear I have been replacing soldered 2x32 batteries with a
holder and a 2450.  The 2450 produces the same voltage - it also has a
higher mA-hr rating, which will last longer.


On 6/3/21, Brian Willoughby <brianw at audiobanshee.com> wrote:
> Speaking of the spec, do you have a spec for the Varta Mempac? The data
> sheet might have such details as the maximum recommended trickle-charge
> current. If you can find specs, you can work backwards from those to see
> whether it's compatible with the Cheetach MS800 circuit.
> As for replacement with a coin cell holder, I've had bad experience with
> that. Every used synth that I've purchased needs to have the coin cell
> replaced very frequently. In contrast, the same CR3032 soldered onto the
> board performs a lot better than a CR2032 in a holder.
> In contrast, I have no experience replacing a NiCd with a CR2032. Given the
> risk of battery acid damage, I suppose there might be a good tradeoff to be
> made. I've never had a soldered CR2032 leak, so I always replace them with a
> soldered model after they expire. The rechargeable are admittedly a
> different story.
> Brian
> On Jun 3, 2021, at 08:51, Joel B wrote:
>> 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
>> On Jun 3, 2021, at 8:10 AM, Mike Bryant 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: Richie Burnett
>>> Sent: 03 June 2021 15:30
>>> 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,
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