8 Jul
2004
8 Jul
'04
7:18 a.m.
On 8 Jul 2004 at 0:44, Jay West wrote:
I noticed this the other day... I'm a bit confused
as to it's lineage.
Would you have a URL to the picture (I'm not an e-Bayer :-)?
First, the M series has a unique keyswitch, unlike the
E and F series.
In the E & F, the keyswitch is nothing more than a latch to open the
front panel. On the M series, the front panel switch is electronic,
selecting R (reset memory I think), Off, Standby, On, and perhaps Lock
(going from memory).
R, Standby, Operate, Lock.
The front panel key changed from an electrical switch to a mechanical lock
coincident with the change from the "A" model power supply to the "B"
model
supply. The M- and E-series were produced in both "A" and "B"
versions
(models 2105A, 2108A, 2112A, 2109A, and 2113A, superceded by the 2108B,
2112B, 2109B, and 2113B). The F-series was produced only with a "B"
version supply, as far as I know. The "A" power supply had the line switch
on the rear of the unit. The "B" power supply mounted an internal line
switch and a separate "Lock/Operate" switch on the front of the supply
behind the front panel that replaces the "Lock" function of the original
front-panel switch.
The front panel itself underwent a number of cosmetic changes. As I
recall, the "A" units were marked "21MX" and "21MX/E" on the
front panel.
The "B" units were marked "M-Series Computer," etc. The HP badge
tended to
move around too from revision to revision.
(My company had one of the original M-series units, i.e., before it was an
"M-series." The power supply was subsequently upgraded to a "B" unit,
necessitating a corresponding front panel change. So my unit originally
had the electrical switch, and now it has the mechanical one.)
The one on ebay has no such markings on the front
panel. This would
make me think E & F. But the front panel is clearly from an M, as it
only has the ABSTPM registers, not the special register mode (index
registers, etc.).
Could be a 2108B or 2112B.
-- Dave