[sdiy] Cheetah MS800 replacing NiCd Varta Mempac

Todd Sines sines_list at scale.la
Fri Jun 4 16:33:38 CEST 2021

I’ve got my 808 on the bench and need a 4.5V cel — any suggestions to bypass 3x AA’s?


> On Jun 4, 2021, at 12:26 AM, Michael E Caloroso via Synth-diy <synth-diy at synth-diy.org> wrote:
> 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.
> MC
>> 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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