Fx-128mt Cpu Board Failure

[gruntstripe 0]

Hello, Don't know too much about plcs'. Got into work yesterday morming and was confronted with an FX-128 with cpu error led on. Flicked the RUN/STOP switch and power cycled whole unit but to no avail. Back-up battery looked like it had been leaking but the voltage was ok. Got the laptop out but had problems establishing comms (communication error). Kept trying and eventually got comms but then got parameter error. Cleared plc memory but could not succesfully download the prog back in. Anyway had to order a new unit and 8k ram module. Production in most of factory down until this afternoon. Put the new kit in with no problems - everything seems ok - touchwood. After lots of messing around on the bench with the old unit we've concluded that the cpu pcb is iffy. The low batt led doesn't light with no battery installed (unless I put my finger on certain parts of the pcb - it then comes on). And it seems the parameter errors are to do with the 2K base memory (and 8k module) not being seen by the laptop software i.e memory chips trashed. Thing is - what could have caused this? Could there have been a mains transient? The psu seems ok as all voltages (5V 12V and 24V) seem ok. All the other kit connected to the base unit (hmi, RS232 module and various extension units) is ok. Or do they just fall over occasionally? Could any condition on the I/O lines have caused this? Can replacement cpu boards be obtained anywhere and at what approximate cost? Is it wise to put surge protectors in a plcs' supply line? The manual doesn't suggest anything so I assume they're not considered necessary. Sorry for the long post. Thanks in advance. Edited 28 Mar 2006 by gruntstripe

[Goody 5]

It may or may not be a coincidence but in the last 2 years I have had 3 faults almost the same as yours All Were FX cpu's - but these were 64 I/O and with 8k eprom. I replaced the entire units and put the eprom in the new units. When I say new, the suppliers still had some on the shelves. Maybe the FX line has run its life Think about repalcing the whole unit with maybe an FX2N

[Crossbow 295]

You should consider FX3U to replace it not FX2N. FX2N is still current product, but the FX3U will replace it eventually. Depending on the model, we have most of the FX3U line released in the US. Most recently the 128 I/O CPUs and transistor output units were made available. FX3U adds new features going forward, like SSCNETIII motion control and Ethernet communications. There's a minimal (max 10%) price difference between FX2N and FX3U.

[Goody 5]

You are right crossbow - I forgot. I have not had the pleasure of the FX3 line yet. I went to the launch of them and was impressed but I have not used one yet.