Home Forums General Discussion Technical Questions Old Miprom P/S Brown out

Have a early 80's 2 stop miprom that doesn't want to come online. Started failing by picking the starter and dropping out within .5 seconds, then picking and dropping.... and so on. When the starter dropped out the reset led indication would come on. Also, all the green LEDs on the output card would flash in time with the starter/reset LED. Have all the correct voltages on the backplane but the output card isn't outputting and the reset LED never goes out indicating that the voltage isn't at the proper level. Any help is greatly appreciated.

Is the ms starter electronic???

Starter is not electronic. Prior to complete failure it was acting like power was dropping too low thus de-energizing the starter then starting over again. Think its called short cycling by some. Thanks

having problems of this sort requires you to have some replacement boards on hand. you really can't trouble shoot this sort of problem. It can be caused by a bad cpu board, a bad power supply board, a bad input or out put board, or bad card rack. Also program boards can cause the shot gunning effect you have described. You can try unplugging the inputs one at a time and see if it stops. I would replace the cpu first. Adams carries most of these boards. Good Luck.

I was afraid somebody was gonna say that. Unfortunately we don't have any boards on hand for this type of elevator to change out.

Will see what we can find out tomorrow.

Thanks for the response.

check the cpu to see if the red led is coming on, it should only come on once , then go out quickly. if it comes on again after going out the first time, you can unplug all the input and output boards from the rack, you dont need to remove the connectors, jus make sure the boards are not plugged into the rack. then turn on the power and look at the cpu, the little red led should come on once and go out indicating the program is running. if it still continues to go on and off, then it is most likely the power supply board. occasionally it is the cpu board or timer board or prom board. and far less likely is the rack itself. if the cpu led comes on and goes out correctly with the i/o boards removed, then it is one of them, just plug one in at a time until the problem occurs, and that will be the bad board. It is probably the powersupply board, this is the one i have found to cause this problem 90 percent of the time

I had the same exact problem on an identical unit last week. It's the 24vdc power supply that mounts to the left of the card rack. you should see 24vdc minimum output at the plus and minus terminals on the capacitor at the power supply.

Follow-up regarding the brown-out problem.

If left alone for a few hours or overnight the voltage level would get high enough for the reset indicator on the power supply board to go out. When this happened the output LED's (green LED's) would come on. As soon as we tried to run, the reset light would come on and it would drop power to the output board.

Replacing the power supply board rectified the problem.

FYI world electronics repairs the boards for 1/3 the cost of adams.

Thanks for all your help!