HP9114B battery pack

From: Carlos Murillo <cem14_at_cornell.edu>
Date: Mon Feb 21 23:59:27 2000

At 12:05 AM 02/22/2000 +0000, you wrote:
>I've got a (non-working) HP9114B HPIL disk drive on the bench at the
>moment. The first few problems seem to be related to the battery pack.
>HP consider this to be a non-serviceable item, so there's no informtion
>available. Needless to say I disagree, and intend to repair it.

Good.

>Firstly the battery itself. The original one is missing, but I think it's
>some kind of sealed lead acid unit, 6V at about 2.5Ah. The largest
>'Dryfit' that I can get that will fit in the housing is the 1.2Ah one. I
>guess this will work but will give me short battery life.

The original packs carried the Panasonic LCR-226P, 6V, 2.4AH, which
are not produced anymore. However, the LCR-062R4PU has the same
form factor and capacity, and can still be obtained. I bought several
at Digikey a couple of years ago. The only difference is in the location
and orientation of the terminals, but bending them a little is enough
for the battery to fit in the pack. By the way, I also used some of these
to replace the larger 3.2AH cells in my HP3421's. Unfortunately, I
could not find any modern battery with the same form factor of the
original LCR-306P.

>However, it appears that 3 off 2.5Ah Cyclon cells would fit in the
>housing. Has this ever been tried, and does the HP charger PCB charge
>these correctly without damage?

The 1.5 V difference is big enough that the charger may actually
damage them. Low duty lead-acid batteries are supposed
to be charged using constant voltage (with initial current limiting,
one amp for the ones in question). For standby use the charging
voltage for these is 6.9V; for cycle use the charging voltage
is 7.3V . Both are way too high for a 4.5V nominal pack. And
I think that 4.5V is probably too low for the hp9114.

I have two HP9114's, an "A" version and a "B" version. The charge
circuits are different. The pack in the "A" version is nothing more
than a series NPN/Zenner base voltage reference plus a fuse in series
with the 9114A. The one in the 9114B does have the LM311, a 79L05,
a 2N3906 and a 6102N/6240 marked "Q2", plus a couple zenners,
an 1N4004 and other resistors/caps. Q2 could also be an SCR (not
the first time one would have shown up in a charger).... in fact,
I have just taken some readings and it definitely is not a bipolar
transistor. It's looking more like an SCR. The gate would be the
pin farthest from the board edge. And this charger is
functional. Sorry, I don't know what a proper replacement would
be, but I think that your Q2 might actually be good (it's hard to
blow up an SCR with a source that has an internal impedance as high
as that in a 82059 xformer).

>Secondly, I have a fault on the charger PCB. This is a fairly simple
>circuit (based round an LM311 comparator) to rapidly charge the battery
>when it's flat and thento fall back to a trickle charge when the battery
>voltage rises.
>
>The switchover seems to be controlled by a 3 terminal component indicated
>as 'Q2' on the PCB. The markings on the device are :
>
>6142N
>M (Motorola logo)
>6240
>
>I assume it's an NPN power transistor, in which case it's defective as
>the collector-base junction is open. But I can't find 2N6240 or 2N6142 in
>_any_ databook or catalogue here (assuming that's what it really is).
>
>Does anyone know what this component is, and does anyone know a suitable
>replacement?
>
>-tony
Received on Mon Feb 21 2000 - 23:59:27 GMT