Brad P

I had a meter connected. I never saw a voltage drop when the LED went out. It is always 120 volts AC.

This problem has happened several times before I added the second power supply to the rack. I have never seen anything saying that I can't have two power supplies per rack. Needless to say that didn't help or hurt the problem. The LED on the power supply is fading off and then comes back on. Most of the time it is off. I have tried using a UPS as a power condioner in the past, but that didn't help. When the LED is off I read 120 volts.

This problem has happened several times before I added the second power supply to the rack. I have never seen anything saying that I can't have two power supplies per rack. Needless to say that didn't help or hurt the problem. The LED on the power supply is fading off and then comes back on. Most of the time it is off. I have tried using a UPS as a power condioner in the past, but that didn't help. When the LED is off I read 120 volts.

I have a CompactLogix with a 1769-L35E processor with two racks. Rack one has 11 cards and rack two has one card.The problem I am having is the power supply (1769-PA4) goes bad about every 3 to 5 months. Or I am assumming it goes bad. What I see is the power supply LED goes off and on. The cards in the rack are blinking and the processor is faulted and has lost its program. The only way I can get it running is to replace the power supply and download a program into the processor. This has happened atleast six times in the past three years. The last time this happened I installed an extra power supply on the rack. Even though the one power supply is all the rack requires. See attached picture. But I continue to have the same power supply fail. I believe I am losing the program because the processor is going into a hard fault. I have replaced every power supply, I/O card and processor on this rack. Any ideas why I am losing this power supply? Thanks.

We had a power supply go bad on another PLC. I used my shop test bench PLC's power supply to make the repair. When the new power supply arrived on installed it on my shop PLC. The only other thing we were doing with the shop PLC, was we were doing a memory card program back up. I guess I will send it to our AB distributor and have AB look at it. Very strange. Thanks for your help.

Thanks for your reply. The key switch will not take it out of run. I can take it out of run remotely using the software. I did a power supply change on this PLC. The power supply input voltage was set at 220V by default from Allen Bradley. I am using 120 volts. I applied voltage (120v) to the power supply that had the 220 volt dip switch set. One power up. Do you think this would cause this problem? Also we were installing a memory card when I noticed this problem. Thanks.

This is in our shop. It is the only one I am connected to. It works fine, But the OK light doesn't come on and the key switch doesn't switch between RUN,REM and PROG.

I have a AB CompactLogix L35E. I can communicate with it remotely with my laptop. I can make program changes. I can switch from RUN to PROGRAM using my laptop. The L35E(PLC) display light never shows the OK light on. Also when switching the key switch from REM to RUN to PROGRAM nothing changes. It is like it is stuck in REMOTE RUN from the computer. In the computer software Ithe OK light is on. When I fault the fault it turns RED like it should. But only in the software. Any suggestions why this is happening? Thanks, Brad