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.

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 €œall okay€�
three tone self-diagnostic (don't know the implication of the missing tone).

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???

Many thanks!

"powerseed" u43512@uwe writes:

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.

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 €œall okay€�
three tone self-diagnostic (don't know the implication of the missing tone).

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???

First things to do would be to confirm

(1) that the serial port adapter has installed properly. I've used this or
a similar unit and the installation can be buggy especially when switching
to a different port. Either connect it to another PC with a known working
seerial port or select in a terminal emulator that is known to work with
COM5 and see if loopback works.

(2) that the tablet is actually outputting something on the serial port.
Make sure it either doesn't need any hand-shake signals (CTS, RTS, etc.)
or that they are set properly.

(3) that the cable has pins 2 and 3 swapped, or not swapped as required.
When connected correctly, there should probably be a negative voltage
on both pins 2 and 3 with respect to pin 5. If incorrect, then
there will be a voltage on only one of those pins.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

Hi Sam...really appreciate your time and input!

Sam Goldwasser wrote:

First things to do would be to confirm

(1) that the serial port adapter has installed properly.

I don't have access to another PC w/ a serial port and am not a programmer
with familiarity with terminal mode (what can you expect from a clueless mac
user . I am pretty confident tho that this is a tablet problem as you may
concur after reading my following responses.

(2) that the tablet is actually outputting something on the serial port.

Serial port switches set to mfr's defaults re handshake, etc. I am also non
compos mentis when it comes to troubleshooting electronics but it did give it
a shot. I have a cheapo R. Shack digital auto-ranging digital multimeter
(that produces wandering phantom readings when not connected to a live
circuit). I tried to document output from the DB9 female on the serial
adapter with the board powered up. Nada when I put the black lead on P5
signal ground and the pos on P2 (during this test I was moving the puck and
pressing buttons as well). When I tested P5 and P2 it would momentarily show
0 volts as I was moving and clicking then it begin its up and down wandering
again???

(3) that the cable has pins 2 and 3 swapped, or not swapped as required.

I'm not using a serial cable...DB25 female plug to male DB25/female DB9
adapter to DB9/USB adapter to USB cable to PC

When connected correctly, there should probably be a negative voltage
on both pins 2 and 3 with respect to pin 5. If incorrect, then
there will be a voltage on only one of those pins.

See above...and my responses to Frank Zabkar in this thread.

My best,

Bill Curry

--
Message posted via http://www.electronicskb.com

"powerseed via ElectronicsKB.com" u43512@uwe writes:

Hi Sam...really appreciate your time and input!

Sam Goldwasser wrote:

First things to do would be to confirm

(1) that the serial port adapter has installed properly.

I don't have access to another PC w/ a serial port and am not a programmer
with familiarity with terminal mode (what can you expect from a clueless mac
user . I am pretty confident tho that this is a tablet problem as you may
concur after reading my following responses.

(2) that the tablet is actually outputting something on the serial port.

Serial port switches set to mfr's defaults re handshake, etc. I am also non
compos mentis when it comes to troubleshooting electronics but it did give it
a shot. I have a cheapo R. Shack digital auto-ranging digital multimeter
(that produces wandering phantom readings when not connected to a live
circuit). I tried to document output from the DB9 female on the serial
adapter with the board powered up. Nada when I put the black lead on P5
signal ground and the pos on P2 (during this test I was moving the puck and
pressing buttons as well). When I tested P5 and P2 it would momentarily show
0 volts as I was moving and clicking then it begin its up and down wandering
again???

This sounds like it's doing something.

(3) that the cable has pins 2 and 3 swapped, or not swapped as required.

I'm not using a serial cable...DB25 female plug to male DB25/female DB9
adapter to DB9/USB adapter to USB cable to PC

When connected correctly, there should probably be a negative voltage
on both pins 2 and 3 with respect to pin 5. If incorrect, then
there will be a voltage on only one of those pins.

See above...and my responses to Frank Zabkar in this thread.

I'd go with checking the power supply/requirements as mentioned in
the other reply. Indeed, if it specifies 12 VAC, it probably won't work
correctly on 12 VDC (but won't be damaged either).

The fact that you're getting no change in the LEDs also suggests that
it's not a communications problem. Probably not getting through self
test due to the power issue.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

Sam Goldwasser wrote:

I'd go with checking the power supply/requirements as mentioned in
the other reply. Indeed, if it specifies 12 VAC, it probably won't work
correctly on 12 VDC (but won't be damaged either).

The fact that you're getting no change in the LEDs also suggests that
it's not a communications problem. Probably not getting through self
test due to the power issue.

Yes...so will get the right power supply and see what happens. Will let you
know.

Thanks Sam!

Bill

--
Message posted via ElectronicsKB.com
http://www.electronicskb.com/Uwe/For...epair/200805/1

On Mon, 12 May 2008 17:28:30 GMT, "powerseed via ElectronicsKB.com"
u43512@uwe wrote:

I'm not using a serial cable...DB25 female plug to male DB25/female DB9
adapter to DB9/USB adapter to USB cable to PC

I would not expect regular function from this serial/USB adapters.
They can work, but it is not guaranteed

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
--
Please remove one 'i' from my address when replying by email.

Great to hear you have experience with tablets...and I appreciate the
mentoring very much!!

Franc Zabkar wrote:

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

Yep, had it.

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

Vtablet settings at both ends.

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.

This sounds like a great idea...will see I can find an old PC to 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.

This is beyond my PC skills at present;-)

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.

Looks like thru-hole soldering to me.

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.

See http://www.powerseed.com/microgrid/Photos.html for pix you requested.

Other points:

**The left LED (yellow) on the puck is supposed to be on when the 16-button
cursor is in use, and off when the stylus is being used. It is alway off in
all my tests. The middle (green) LED is supposed to come on when the puck has
proximity (within the table's electromag field)--it always glows dimly when
the table is powered up. The third LED glows dimly all the time also...it's
for programmable alerts.

**The tablet came sans power supply. Based on the specs I picked up a 12volt,
1 amp supply. Manual says mfr's p.s. must be used or wtty is void. Is this a
possible issue?

**I note there are what appear to be contact tabs (labeled +12v AC, -12v,
+12v, +5v, DIG GND, DIG GND) at the bottom right (plan view). Are these for
test fixture powering?

**Misc.--Unknown variable...There are also two blue, 2-receptacle "pin
jumpers" (labeled W3 and W5) seen at the bottom center of the board (plan
view). Each jumper has two possible positions (left or right) among 3 pins.

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

I did this a while ago with no response. Current s/w (Cartalinx, Clark Labs)
programmed for Vtablet.

Thanks Franc!

--
Message posted via http://www.electronicskb.com

On Mon, 12 May 2008 18:12:53 GMT, "powerseed via ElectronicsKB.com"
u43512@uwe put finger to keyboard and composed:

**The tablet came sans power supply. Based on the specs I picked up a 12volt,
1 amp supply. Manual says mfr's p.s. must be used or wtty is void. Is this a
possible issue?

Page 15 of the manual states that the tablet needs a 12V ***AC*** 1A
power supply. Instead you have provided a 12V ***DC*** 1A power pack.

**I note there are what appear to be contact tabs (labeled +12v AC, -12v,
+12v, +5v, DIG GND, DIG GND) at the bottom right (plan view). Are these for
test fixture powering?

Maybe. Measure them with a multimeter. I'm betting that the +12VAC
(???) and -12V rails will be missing. The -12V is required by the
tablet's serial port, and possibly by the analogue circuitry for the
digitizing surface, and for various op-amps.

I'm betting that the 2-tones error indicates a problem with the
analogue circuitry.

If you get your MG3 working, I would still run the MG3TEST. I've seen
lots of tablets with dead spots on the surface, usually caused by dry
solder joints, or bad driver chips (yours appears to use the ULN2003
chips).

BTW, if you ever need any spare ICs, keep me in mind. I have a lot of
chips of that era ... somewhere. You'll just need to pay for postage
from Australia. I also have a new unused 4-button Summagraphics puck,
but that cost me money.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Franc Zabkar wrote:
**The tablet came sans power supply. Based on the specs I picked up a 12volt,
1 amp supply. Manual says mfr's p.s. must be used or wtty is void. Is this a
possible issue?

Page 15 of the manual states that the tablet needs a 12V ***AC*** 1A
power supply. Instead you have provided a 12V ***DC*** 1A power pack.

Oye-- How dumb is that!!! So this is just a step-down transformer!! I thought
all the bricks were AC to DC. Do you think using 12v DC could have hurt the
board? Or that it could be the source of my problems??? Not many of these
supplies out there. Did find one with a 3' cord though that I will pick up.

**I note there are what appear to be contact tabs (labeled +12v AC, -12v,
+12v, +5v, DIG GND, DIG GND) at the bottom right (plan view). Are these for
test fixture powering?

Maybe. Measure them with a multimeter. I'm betting that the +12VAC
(???) and -12V rails will be missing. The -12V is required by the
tablet's serial port, and possibly by the analogue circuitry for the
digitizing surface, and for various op-amps.

Didn't get any current when board was plugged into my !@$#$@% power supply--
perhaps AC will make a difference.

I'm betting that the 2-tones error indicates a problem with the
analogue circuitry.

I also saw at p. 40 of the UG that there are THREE MG3TEST diagnostic tests:
RAM, X-axis, and Y-axis--perhaps corresponding to the 3 tones??? Or not! If
so tho, might suggest Y-axis circuitry.

If you get your MG3 working, I would still run the MG3TEST. I've seen
lots of tablets with dead spots on the surface, usually caused by dry
solder joints, or bad driver chips (yours appears to use the ULN2003
chips).

One ULN2003...along with six UDN2595-A dips which I think are drivers.

BTW, if you ever need any spare ICs, keep me in mind. I have a lot of
chips of that era ... somewhere. You'll just need to pay for postage
from Australia. I also have a new unused 4-button Summagraphics puck,
but that cost me money.

Will keep all that in mind!

Thanks!

--
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http://www.electronicskb.com/Uwe/For...epair/200805/1

On Tue, 13 May 2008 01:57:41 GMT, "powerseed via ElectronicsKB.com"
u43512@uwe put finger to keyboard and composed:

Franc Zabkar wrote:
**The tablet came sans power supply. Based on the specs I picked up a 12volt,
1 amp supply. Manual says mfr's p.s. must be used or wtty is void. Is this a
possible issue?

Page 15 of the manual states that the tablet needs a 12V ***AC*** 1A
power supply. Instead you have provided a 12V ***DC*** 1A power pack.

Oye-- How dumb is that!!! So this is just a step-down transformer!! I thought
all the bricks were AC to DC. Do you think using 12v DC could have hurt the
board? Or that it could be the source of my problems???

As Sam has said, DC won't hurt your tablet. Using DC instead of AC
means that some negative voltages are not able to be generated within
the tablet for important functions such as the serial port and for
your signal amplifiers (op-amps).

I'm betting that the 2-tones error indicates a problem with the
analogue circuitry.

I also saw at p. 40 of the UG that there are THREE MG3TEST diagnostic tests:
RAM, X-axis, and Y-axis--perhaps corresponding to the 3 tones??? Or not! If
so tho, might suggest Y-axis circuitry.

I suspect that the power-up sequence starts with a basic digital test,
ie ROM/RAM/CPU check, after which the first tone is output. Then
perhaps the next level of circuitry is tested (eg the 2651 serial
controller chip), resulting in a second tone. The next and final set
of tests may involve the analogue circuitry, ie the X & Y wires, which
would fail in this case because of the missing -12V rail. But that's
just a WAG ...

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.