Light Machine Corp. Benchman XTr (retrofit)

I tried communicating with the ATC through Hyperterminal but wasn't able to get any kind of response from the machine. I hooked up an oscilloscope to the test points on the ATC board for the RS232 communication (Test Points 18, 6, and 7) and saw the square wave form. Seemed to be static for TX, not sure if it was the same byte repeating. The Max233 RS232 interface seems to be working fine, it's dropping the the waveform amplitude down to around 5V.

When I try to operate the ATC I keep getting the message "ATC send command error" and the software freezes up. What exactly does the ATC Reset button do?

The button on the board SW1 triggers the manual reset on the MAX705 IC (U25) to trigger a soft reset to U4.

Please note that J2-5 (TP6) is the data IN to the ATC and J2-3 (TP7) is the data OUT of the ATC. For some reason the schematic incorrectly has the input marked TX and the output marked RX.

Do you have +5V, are U25-7 and U25-5 both +5V?

U25-7 has +4.77 V, but U25-5 has 0 V.and if I'm reading this right, it looks like U25-5 is the power for the U10 microprocessor. Why would that be zero volts? U25-6 has +5 V. Just to be sure I probed U10-14 and was 0 V also.

In regards to the Tx and Rx signals at J2, the Tx signal at TP6 looks static, but Rx at TP7 looks much more "active",on the scope, if that makes sense?

If U25-5 is low, then the system thinks it is in the middle of a power fail.
U25-5 will only be low when U25-4 is below 1.25V.

Is TP1 +5V when referenced to TP19?
What is the voltage on U25-4?
If it is lower than 1.25V, check R1 and R2.

Attached is the MAX705 Pin Descriptions.

U10 power is through Pin 44(+5V) & Pin 22(GND).

It turns out I was measuring the wrong pins on U25. Pin 5 does have +5V, so it doesn't look like that's the problem.

I talked to tech support at Intelitek today and they do have a few of the ATC cards still in stock, for over $1000. And they need the old card in order to swap out the logic chips to the new card. So if the chips are the problem there's really nothing they can do.

Was there any chance they would test/evaluate yours?
I'm not sure why they would need your chips, they should have the programs. Perhaps it is the availability of the physical chips.
The last time I spoke with them, they still had a couple of the XT type machines there and were doing testing for others with them.