On Sat, 10 May 2008 14:08:01 GMT, "powerseed" u43512@uwe put finger
to keyboard and composed:

This equipment (a Microgrid III 36" x 48" graphics digitizing tablet ca 1992)
is a tad esoteric at this point..no factory service, tech manual available,
etc. I'm a student trying to resurrect this old bird for my GIS classes.

Serial interfacing software (Vtablet) is available for connecting this to my
XP Pro Compaq laptop. I bought a serial port to USB adapter (Keyspan) for my
MGIII which self-installed at COM5. Since the COM1 port was occupied, I reset
the serial Keyspan adapter via the Windows Device Manager to COM2 and set
Vtablet to COM2 as well. Following recommended start-up procedure (Microgrid
tablet on, then boot) I am unable to elicit any puck output (screen cursor
movement in response to moving the puck on the tablet) which is also
confirmed as zero port interrupts on the software's Status tab.

This is the user manual:
http://www.gtcocalcomp.com/files/Microgrid3.pdf

Make sure you have matched the communications parameters (baud rate,
parity, etc) at both ends of your cable.

Here are some recommended settings when used with Vtablet:
http://www.vtablet.com/download/Digitize.txt

To narrow down your problem, you could connect your tablet to a PC
with a real serial port and try this suite of test programs:
http://www.gtcocalcomp.com/files/sgdosdrv.exe

It includes an MGIII test.

Alternatively you could try a DOS terminal emulation program such as
Telix or Xtalk which can display incoming data in hex mode. You could
also set the tablet switches for ASCII output mode.

I am now concerned that the tablet controller is misbehaving . I also note
that the Microgrid start-up only produces two tones instead of the “all okay”
three tone self-diagnostic (don't know the implication of the missing tone).

The user manual says that anything less than 3 tones means your tablet
has a problem. On the plus side, the fact that it produces any tone at
all suggests that the CPU and ROM are probably OK.

If the PCB has socketed ICs, then you could remove them one at a time
to see if the error tones change. For example, if removing a RAM chip
changes your error report from 2 tones to 1 tone, then you can be
reasonably confident that your RAM is OK.

The unit has a removable 8" x 13" controller board and I was wondering if
anyone out there could direct me to an circuit troubleshooter who could look
it over and hopefully repair???

Can you upload a photo to your web space? It may jog my memory.

Many thanks!

You could try TabletWorks as an alternative to Vtablet:
http://www.gtcocalcomp.com/supportsummasoftware.htm

- Franc Zabkar
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