[sdiy] Cheetah MS800 replacing NiCd Varta Mempac

Richie Burnett rburnett at richieburnett.co.uk
Thu Jun 3 16:29:59 CEST 2021

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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