[sdiy] Cheetah MS800 replacing NiCd Varta Mempac

Mike Bryant mbryant at futurehorizons.com
Thu Jun 3 17:07:10 CEST 2021

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!


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