HP 21MX E-series front panel keyboards

From: Bob Shannon <bshannon_at_tiac.net>
Date: Wed Jan 26 20:50:46 2005

There are two ribbon cables between the CPU board and front
panel, except when there is only one.

This actually makes a little sense.

Only one ribbon cable is needed for a standard CPU to
talk to the front panel. The extra ribbon cable connection
point on the full sized front panel may be ignored.

So HP CPU configurations add a 'booster' microcode board
to the standard CPU board. In these configurations the CPU's
MPP port (a fast I/O port for microcoded data transfers) gets
the second ribbon cable.

There are two major types of full sized front panels, those
with open leaf contacts for the buttons, and those that use
the small snap disk switches.

Electrically these are identical, mechanically the snap disk
panel is superior.

The 'short' front panel used on the smaller boxes ~might~ be
either of these boards, as its much shorter than the height of
a 2113. There may also be a smaller version for the really short
CPU box, I'm not sure about that.

Short box CPU's seem to be much less common than the
full 2113 box.

If you want to convert your 5320 CPU to a stock 2113, I have
all the chassis parts you would need to rebuild the processor in
the tall 2113 box.

----- Original Message -----
From: "Peter Brown" <peterbrown10_at_hotmail.com>
To: <cctalk_at_classiccmp.org>
Sent: Wednesday, January 26, 2005 12:56 PM
Subject: RE: HP 21MX E-series front panel keyboards

> Hi All,
> How many types of front panel keyboard were used with the 2113 E-series
> CPU?
> I have one in front of me that has two ribbon cables that run from the
> keyboard PCB to the CPU PCB (one from the top edge of the keyboard PCB one
> from the bottom edge) but I seem to remember having seen other 2113 CPU's
> where the keybaord PCB is smaller and a single cable runs from the bottom
> edge of the keyboard to the CPU PCB.
> What I'm trying to do is find a 'short' front panel to replace the
> 'embedded' keybaord of a 5420 Signal Analyser and turn it back into an
> mini E-series CPU.
> I had assumed that I would be able to unbolt the top of a 2113 front panel
> and use just the keyboard portion of the assembly but the PCB behind the
> keyboard that I have turns out to be too tall! Is there is shorter one
> available.
> Can anyone shed any light on this one?
> Cheers
> Peter Brown
Received on Wed Jan 26 2005 - 20:50:46 GMT

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