Dynapath 20 COM port ICs

[tony@eCV]

I purchased a used Tree mill with a Dynapath 20 controller and I am pretty certain that the RS-232 COM port is blown. Does anyone have schematics to identify the blown chips?
Thanks much.

[underthetire]

Why do you think the comm port is blown? If you look on the label of the RS232, i believe it says parallel port, so lines 2&3 are different then a serial port. You will need a light box to determine if it is actually blown. about a 10 dollar item at radio shack if they still carry them.

[tony@eCV]

The DB-25 connector on the Dynapath is wired as an RS-232 port (they did that years ago before they switched to the DB-9). I have tried to download a program from a PC serial port using both a null modem and straight-thru cable with no success. After several hours on the web, I found that a blown COM port IC is fairly common on these units - probably due to static discharge.
How would a light box help me determine if an IC is blown?

[Southbend Sam]

The light box (mine is called an RS232 mini-tester) will determine if a signal is getting to yourRS232 port when the PC is sending and if a signal is leaving the RS232 port when sending a program. I had troubles setting up an RS 232 connection with my Dynapath 20. I ultimately determined I needed to have pin 2 (db-9 connector) go to pin 3 (db-25) and pin 3 (db-9) go to pin 2 (db-25). One of the problems I had is that the null modem cable for db-9 to db-25 had pin 2 to pin 2 and pin 3 to pin 3. At any rate the light box will give you definite information on whether your port is working or not.

[rbickle]

Tony,

I will have to open my Dynapath controller and look, but equipment from this time period generally used two chips for RS-232 communications interfacing. These are the 1488 (driver) and 1489 (receiver) chips. These chips are used to translate the RS232 levels +12vdc and -12vdc to 0vdc and +5vdc respectively. When the serial port blows, these chips are usually the culprit.

Rick