DEC RK05 Emergency Retract Batteries

tony duell ard at
Mon Mar 14 12:52:12 CDT 2016

> It's now foggy memory, but I'm pretty sure HP 7900A (and 7901) were using
> batteries for emergency head retract.

The 7900 certainly does (there is one to go on my bench when I have some
spare time). In that case it's some AA-size NiCds (not tagged ones) in those
aluminium clip-in holders (Radio Shack used to sell them, I think Mouser still

The DEC RK07 (and I assume RK06) used 8 1/2 AA cells in a pack (like
2 RK05 retract batteries in series). When I replaced those, I used 2 of
the cordless telephone batteries (that have been recommended for
the RK05) in series.

I am told some later drives used the spindle motor as a generator when the
power failed to provide the power for emergency retraction.


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