ATL UM400C System Will Not Boot.

 

Answer: The first step to troubleshooting the problem is to see if the main monitor is the culprit or not. If the unit has the small monitor to the right of the main monitor see if it is active. Also, if there is a printer, try printing from it to see if there is any information being displayed. If there is video on the small monitor and/or the printer, most likely there is a problem with the main monitor or the power/video going to it. Power the unit down, reseat all connections to the monitor and from the system to the monitor. Power up the system and see if the problem is corrected. If not, the next step would be find another monitor with the same type of connections to rule out a bad monitor before replacement. If trying a different monitor does not work, the next step is to replace the Output Board.

 

If all video is dead, (main monitor, small monitor, printers, etc.), the problem is most likely a board hanging up the bus or a bad power supply voltage. I would check all low voltage power supply voltages (+/- 5vdc, +/- 12vdc) on Con2, Con3, & Con6 first to ensure they are within tolerances and no more than 1.0 VPP of AC ripple is present. If the power supplies look good, try removing one board at a time from the backplane, (with the power off) to see if the unit will boot. If the unit boots after removing a board, that last board you removed is the likely culprit. If you have removed all the boards and the unit still will not boot, the only thing left is the Pentium PC Board itself.