NVRAM resuscitation (Was Re: SPARCstation 20 with SCSI2SD)

allison allisonportable at gmail.com
Tue Nov 27 18:00:04 CST 2018

On 11/27/2018 03:34 PM, Jeffrey S. Worley via cctalk wrote:
> When I bought that Sparcstation 4/330 at Computer Parts Barn, the 48T02
> was one of the problems with it.  The chip looks like a piggieback rom
> encapsulated in epoxy.
> I was not reinventing the wheel at the time, I think, because it was
> the year 2000 or so, but I looked for a replacement and found them hard
> to come by.  So, knowing the battery was most likely the fault, I went
> about fixing that bit.
> The battery accounts for the high profile.  You do not have to cut the
> entire doggone batter off, the terminals are at one side, iirc, the
> right-hand side if the notch is to your left.  It is high on the epoxy,
> so all you need do is cut down an eighth of an inch in that region,
> just shave that top edge until you expose the battery terminals.  I
> forget how I determined the polarity of them, perhaps I plugged it into
> the board after and tested the terminals for power, but all you do once
> you've exposed the terminals is solder a power and a ground wire to
> them and attach a 3volt battery.  I used a pack with two AA's, in a
> case so they are user-replaceable.  They are probably STILL keeping
> time in that machine, wherever DHS took it and my MEGA ST4 and DG
> MV4000/dc...  That's another story.
> So refurbishing these chips is a cakewalk, takes 15 minutes (the second
> time 'round), and will work til' doomsday.
> Best regards,
> Jeff
I take a very simple approach:

All the ones I've ever purchased were bad out of the box (NOS parts), so
much for china but they can be repaired too.

After removing it from the board...

I use a small magnet to locate the battery.  I use a sharp wood chisel
about .25 wide and carve the plastic down
to the battery then get under one edge.   Once metal is visible I clear
the plastic and pop it out.  The wires then
are easy to locate and I mount using Hot-melt glue a new holder for the
very common 2032.    Never had to
replace one of those and a few are pushing more than 12years.  The whole
mess takes less than a few minutes
to do where access the board and getting it off the board are the bigger
part of it.  Since I have a few NOS
(but dead) parts plus pulls from old CPU cards I rarely worry if the
existing one gets damaged as I have spares.
To me its not a big deal.


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