There are 2 versions of connectors to make a connection between motherboard and 9 pin D-SUB.

Pins:
1 2
3 4
5 6
7 8
9 10

The older is:
DCD DSR
RXD RTS
TXD CTS
DTR RI
GND NC

The newer is:
DCD RXD
TXD DTR
GND DSR
RTS CTS
RI NC

I guess you need a multimeter first...

You can find a desctiption in German here: https://www.qsl.net/dj9rr/COM1-Anschlusskabel … Motherboard.htm
However, if you do not understand German, just have a look at the pictures.

Popaldini wrote on 2021-04-29, 13:40:

COM1 & COM2 serial ports on board via 1o pin connection to 9 pin d-sub.

Verify this.

Does the board have damage from a leaking Varta?

weedeewee wrote on 2021-04-29, 16:26:

Verify this. https://www.vogons.org/thumbs/31670_9d784d0a15ead5763f29f1dbf042a3b1/DTK3a.jpg […]
Show full quote

Popaldini wrote on 2021-04-29, 13:40:

COM1 & COM2 serial ports on board via 1o pin connection to 9 pin d-sub.

Verify this.

Strange description. RS232 is not differential.

I have the same issue and according to my POST card, there is no -12V so the leaking has caused some damage.
Might want to check it out.

Disruptor wrote on 2021-04-29, 17:32:

weedeewee wrote on 2021-04-29, 16:26:

Verify this. https://www.vogons.org/thumbs/31670_9d784d0a15ead5763f29f1dbf042a3b1/DTK3a.jpg […]
Show full quote

Popaldini wrote on 2021-04-29, 13:40:

COM1 & COM2 serial ports on board via 1o pin connection to 9 pin d-sub.

Verify this.

Strange description. RS232 is not differential.

Yeah the pin description on the lower left makes no sense

Disruptor wrote on 2021-04-29, 17:32:

weedeewee wrote on 2021-04-29, 16:26:

Verify this. https://www.vogons.org/thumbs/31670_9d784d0a15ead5763f29f1dbf042a3b1/DTK3a.jpg […]
Show full quote

Popaldini wrote on 2021-04-29, 13:40:

COM1 & COM2 serial ports on board via 1o pin connection to 9 pin d-sub.

Verify this.

Strange description. RS232 is not differential.

You are absolutely right. I hadn't paid much attention to the signal names
Someone on the forum here posted it before, so it's just a link to the image they uploaded

Thanks guys, still cant get it going. According to my Mobo manual the COM header is the AT/everex type. The new ribbon cable I bought is the cross over type, whereas the old one that was in the machine was a straight through (at the level of the d-sub). I tried to re-solder the connection to change to the straight through type but it still didn't work.

The mouse only uses 4 of the pins

Any ideas?

Have you tried some diagnostic tools?
like CheckIT!

Did you check if you have -12V?

Popaldini wrote on 2021-04-29, 18:37:

Thanks guys, still cant get it going. According to my Mobo manual the COM header is the AT/everex type. The new ribbon cable I bought is the cross over type, whereas the old one that was in the machine was a straight through (at the level of the d-sub). I tried to re-solder the connection to change to the straight through type but it still didn't work.

The mouse only uses 4 of the pins

Any ideas?

Have you got a multimeter to test a few things? With the computer off you should be able to measure roughly 0 ohms from pin 5 of the serial port to GND (should be able to use computer case). There should only be one pin that measures 0 ohms, and if it's not at the end of the row of 5 pins on the serial port then the wiring is wrong. Then after you turn on the machine, but don't run anything, you should be able to measure around -12V on pins 3 (TxD), 4 (DTR) and 7 (RTS) - they measure about -10.5V on my machine (black probe to case, red probe to pin on serial port). With my MS Serial mouse then when it's working the driver sets pins 4 & 7 to high (around 10V with the mouse unplugged). If you can check those then you'll know if the header cable is correct.

Are you sure the mouse only uses 4 pins? I was playing with an MS Mouse recently and for serial it used 5 pins: pin 2 (RxD, data from mouse to PC), pin 3 (TxD, -12V to mouse so it can have the correct voltage for transmitting), pin 4 (DTR, +12V for power and signalling level), pin 5 (GND, for running the electronics in the mouse) and pin 7 (+12V, for signalling to the mouse to send an ID byte). I suppose it would be possible to use pin 7 for both power and signalling.

[Ah, just read around a bit and the earlier MS serial mice did just use 4 wires, pin 2,3,5&7. So make sure the pin 5 is GND (measure resistance to the case), pin 3 is near -12V and pin 7 is near +12V (or -12V just after booting)]

snufkin wrote on 2021-05-01, 11:42:

Have you got a multimeter to test a few things? With the computer off you should be able to measure roughly 0 ohms from pin 5 o […]
Show full quote

Popaldini wrote on 2021-04-29, 18:37:

Thanks guys, still cant get it going. According to my Mobo manual the COM header is the AT/everex type. The new ribbon cable I bought is the cross over type, whereas the old one that was in the machine was a straight through (at the level of the d-sub). I tried to re-solder the connection to change to the straight through type but it still didn't work.

The mouse only uses 4 of the pins

Any ideas?

Have you got a multimeter to test a few things? With the computer off you should be able to measure roughly 0 ohms from pin 5 of the serial port to GND (should be able to use computer case). There should only be one pin that measures 0 ohms, and if it's not at the end of the row of 5 pins on the serial port then the wiring is wrong. Then after you turn on the machine, but don't run anything, you should be able to measure around -12V on pins 3 (TxD), 4 (DTR) and 7 (RTS) - they measure about -10.5V on my machine (black probe to case, red probe to pin on serial port). With my MS Serial mouse then when it's working the driver sets pins 4 & 7 to high (around 10V with the mouse unplugged). If you can check those then you'll know if the header cable is correct.

Are you sure the mouse only uses 4 pins? I was playing with an MS Mouse recently and for serial it used 5 pins: pin 2 (RxD, data from mouse to PC), pin 3 (TxD, -12V to mouse so it can have the correct voltage for transmitting), pin 4 (DTR, +12V for power and signalling level), pin 5 (GND, for running the electronics in the mouse) and pin 7 (+12V, for signalling to the mouse to send an ID byte). I suppose it would be possible to use pin 7 for both power and signalling.

[Ah, just read around a bit and the earlier MS serial mice did just use 4 wires, pin 2,3,5&7. So make sure the pin 5 is GND (measure resistance to the case), pin 3 is near -12V and pin 7 is near +12V (or -12V just after booting)]

Thanks for the advice mate, done all the tests above. I can confirm that pin 5 is ground on the continuity check and both pins 3 and 7 putting out around 10.5v like yours.
I guess that means that the serial controller chip on the Mobo is probably screwed or the mouse is incompatible for another weird reason.
I have ordered an ISA card with 2 serial headers and a separate controller on board. Hopefully that will remedy the situation!!!

Murugan wrote on 2021-04-29, 19:04:

Did you check if you have -12V?

Yes mate just checked all voltage and wiring to the serial header is correct. I guess either the serial controller onboard is screwed or the mouse isn't compatible for another weird reason.

Popaldini wrote on 2021-05-09, 15:05:

Thanks for the advice mate, done all the tests above. I can confirm that pin 5 is ground on the continuity check and both pins 3 and 7 putting out around 10.5v like yours.
I guess that means that the serial controller chip on the Mobo is probably screwed or the mouse is incompatible for another weird reason.
I have ordered an ISA card with 2 serial headers and a separate controller on board. Hopefully that will remedy the situation!!!

I think pin 3 should be negative, not positive (in my case, 3 is negative and 4 & 7 go from negative to positive if the mouse is connected). Something has to get a negative voltage to the mouse so that it can send a proper serial signal back to the computer (I suppose the mouse could generate it locally, but that'd be more expensive than just having the driver control the port pins). If you boot the computer without the mouse attached, are any of the serial port pins negative? If there's nothing negative, check that your PSU has -12V as one of its outputs. Also check that you've got -12V on pin B7 of the ISA slot. If you don't then the COM card probably won't work.

Hope I can use this thread instead of opening a new one.
Having some issues with a Genius easymouse on a 386. When the driver is loaded, the mouse can only go left to right and as far as I know the left button works. What could be the problem? On the pcb of the mouse there is nothing that could really gone wrong. In another mouse I have similar problems, but with buttons working and no direction at all! No up/down and no left/right.

Where should I start to search for the problem? The IR emitter? But I guess these are so well built that could hardly go bad...

What mouse driver?
Do you use the mouse in Microsoft (2 button) or Mouse Systems (3 button) mode?

Can you post a picture of your mouses PCB?

I used CTmouse under DOS 6.22
Using it in 2 button mode.

There is the genius easymouse pcb.

Martin85 wrote on 2022-12-14, 17:35:

I used CTmouse under DOS 6.22
Using it in 2 button mode.

Have you tried a different mouse driver?
I've had issues with the ctmouse driver myself.