IBM T41 T42 RS232 output trick

[geser]

Thank you for answer.
I'm not sure shielded wires is needed.

I have an IBM T42 with a little bit different MB. All pads around is not going to the MAX.



That is interesting. External COM port throuht IBM port replicator and internal modem are not working propely. Windows said no problem detected... I'm really confused because if MAX3243 is damaged modem should work, if damaged something else before MAX windows should detect it. Its sems to be hardware issue bacause in dos I'm having same issue.
Does anyone have some ideas?

[malch]

If you look at the picture in my last post, you can see the traces under the green paint[coating].
You could use an ohm meter to ring out the connections between the port replicator db9 and the pins on the MAX.
No idea on the modem.

[geser]

I'd like to say thanks to all members replied this thread. I've completed the COM port upgrade of my T42 by routing 9 teflon shielded wires from MAX to the connector.
VGA connector asembly with built-in lttle switch has been completely removed. This switch is not required if you're not going to 'hot' remove your CD drive or second battery.

Some pictures of upgrade process listed below. Maybe it will be helpful for someone else who are going to add the Serial connector to a laptop.

[malch]

What gauge is the Teflon wire? Where did you get stranded wire that small?
Very nice solder job.

[geser]

Gauge of this wire is 0.07 mm2. Outside wire diameter - 0.75mm. I bought it on a local electrical shop.

There is lots of different gauges of this wire. Here we call them 'MGTF - 07' numbers in title is a gauge. It's a very common use wire.

[malch]

Googled MGTF - 07 and all I got was a old sports car, no wire at all. Lots of strands for outside diameter of 0.75mm.

[geser]

In original title letters s/b Cyrilic. Maybe that's why you couldn't find any wires... Try to paste 'МГТФ' to the search field.

Also maybe someone from CIS or China is selling similar wires on the eBay?

[malch]

Bought this: 30 FT Blue M16878 13 Ptfe Teflon Wire 28AWG Silver Plated High HZ LOW PWR Loss | eBay
but it is only 7 strand

[malch]

The wire I bought is too thick.
edit: I bought a T42 and could not find any solder pads, so I had to solder the wires directly on the MAX like geser.
He has access to very fine wire. got it done though.

[pishta]

My T40 has similar pad traces as Geser, could not trace pinouts of pin 8 and 11 of MAX chip but GND was in many places. Will look into full VGA-RS232 port swap with fine .7mm wires, but I believe you only need 3 wires: 8,11,25. Beautiful solder job. I believe you can trace out these pins to the pads under the tape 1" above MAX chip as they go to the replicator port.

[malch]

pishta thanks for the idea to search under the tape. It would have saved me a lot of time and trouble.
t42 com.jpgt42com.jpg
This is for a T42.
I put an attachment in this post and I cant get rid of it. You can use 178 or 118 for ground.

[pishta]

The wires you need might be 28 or 30 AWG. My be easier to search these. I found 4 very small wires in a flimsy usb cable and they come with a foil shield already around them. The 28G and 30G had a name but i forgot what the salesman called them, but they sure aren't cheap: $15 US for 100 feet! Im hesitant to pull the tape as soldering to the chip traces is a larger target than the small through holes, and heat will be at a minimum as the wire gauge is so small. Ill post pics soon.

[malch]

The wire I bought was 28 GA and it was too thick.
The new solder points under the tape are very much bigger and easier to solder to than the chip legs.
You can see in my first pic the solder points will take 20 GA wire easily, so I will be using the 28 GA I bought.
Also you can strip a 8 or 9 wire cable [mini-din S video] and end up with 8 or 9 wires each with their own colour.

edit: this pinout should be good for any motherboard that connects to a Port Replicator II.

[pishta]

Malch, i tried to solder onto the taped pins but i kept getting a short across pins DB9 3 and 7 even though they looked clean. Can you check your working DB9 pins for any designed shorts across any of the pins? Pin 11 on max chip seems to short across the entire left side of the chip before any solder work? I was using the 4 pins plus a ground : tx rx cts rts and common ground.

[malch]

Thats a short between 180 and 119. There are no designed shorts as far as I can see . On page1-post1, there is a schematic of the motherboard.
Perhaps you used a flux that is conductive. You have to clean the soldered connections with alcohol.
You can really appreciate geser's solder job.