Swap your computer power supply with communcations supply to test. There is 12 v + & - with no test points that is also used to log into unit. If you can log in, run a "B" test for faults. Possible bad Bam Board. Its function is an interface and level converter for I/O to Computer. Also has any boards been replaced. New boards will come with the wrong bipolar proms for the job. Compare Proms with another car for correct versions for your software, Also bad memory board will do that. It is a 900 and not a 9000? 900 is an 8088 processor and 9000 & 900+ is a 286 with ribbon cable from cpu to mem board,

Thanks, that is great info but I do not have a test tool or the software for the laptop.
I will look for an I/O board failure and will change the BAM board as I have some spares.
The units are TMS 900 that have been upgraded to 9000.

Thanks for your help.

You don't need a test tool you can log in with Hyper terminal on XP using 300 baud ( or jumper settings), 7data bits, Even Parity, 1 stop bit, Flow control Hardware. you can log in using password "4#H/"

Thanks once again for the help.
I have found the fault, it was a bad I/O board which was causing the BAM led's to flash.
I set up a spare boards jumpers and plugged it in and the lift worked "OK".