Just thought I'd share a wierd SLC failure!

[gravitar 3]

Here's a strange one I figured I'd share with you guys. I've got a 7-slot SLC chassis with a P2 supply, a 5/01 (w/EEPROM), a medar welding card, and a couple discrete I/O modules. Runs fine UNTIL you power down the rack. When you turn it back on, *poof* no program! the memory is in the DEFAULT state, nevermind that the battery light does not come on and there's an EEPROM with the "Load always" bit set! So it must be a bad processor of course. Swap the 5/01 with another known good one.. NOPE! same problem. Doesn't matter if it was powered down for 2 seconds or 2 hours, the result is the same every time. You can force it to read from the EEPROM when you connect to it, but it won't do it on its own. No fault code, just blank "DEFAULT" memory. Ok so this one is getting wierd. Mind you, once you download or tell it to read the chip, all is well. So what could it be? Who's got a guess.. .. .. .. .. Times up!! It was the rack power supply! Not sure why, as it was providing clean enough power to run the rack all day long. Something's happening at power-down that the SLC didn't like though! My theory is maybe the rack power supply provides some temporary power to the processor so that it can power down properly. There's lots of pins in the power supply connector, so maybe it is doing more than just providing +5, +24, and ground!

[BobLfoot 302]

Nice strange one - What was age of the Power Supply.

[rpraveenkum 5]

May be the problem with the grounding improper grounding cause this type of problems

[OkiePC 14]

I read another post very similar some time ago. They eventually nailed down a failed capacitor within the power supply that was causing the same symptoms you reported. I can't remember where I read about it though...