Elgar SW5250A 3-phase AC Source thinks its a SW1750A

[KSP]

Hi All

I have a beast of an instrument. Its an Elgar AC source, model SW5250A. The problem is an odd one. If I program it over the bus (GPIB in this case) then all phases program up fine. If I do an *IDN? query on it then it returns the model number SW1750A, which is the single phase version of the same unit. Also, from the front panel I cannot access phases B and C. I mean they are literally not there in the menu. But as stated, the physical modules are there and the bus programs them up fine.

Why has my Elgar forgotten what it is? I've replaced the memory battery and reinstalled the firmware but still nothing.

Any ideas?

Being in the UK, I'd quite like to avoid sending it back to Ametek in California. We've done this before and it's not cheap!

Can't seem to find service manuals either, only User and Programming manuals 

[kripton2035]

did you ask Ametek about this problem ?

[Stray Electron]

  Interesting problem!  I take it that it did work correctly at one time?  It sounds like the PROM has tables for multiple models in it and some how it's using the wrong table.  I would look for some other memory device or a GAL that may contain the model number and enables/disables any optional features.   I have have two Elgar AC Sources but they're older and without microprocessor controls.

  You might dump the ROM and look at the contents with a Hex Editor and see if it does show other model numbers.  If it does, then you just have to find a way to make it select the one that you want.

[KSP]

did you ask Ametek about this problem ?

We have not asked Ametek about the problem as of yet. Last time we did that they referred us to their UK repair representatives (a third-party company) who we currently have some bad blood with.

  Interesting problem!  I take it that it did work correctly at one time?  It sounds like the PROM has tables for multiple models in it and some how it's using the wrong table.  I would look for some other memory device or a GAL that may contain the model number and enables/disables any optional features.   I have have two Elgar AC Sources but they're older and without microprocessor controls.

  You might dump the ROM and look at the contents with a Hex Editor and see if it does show other model numbers.  If it does, then you just have to find a way to make it select the one that you want.

Yes it has worked previously, but it is not the first one to show up faults. We have quite a few of these, and there are a couple others which identify over the bus as 1750s but this causes no issue as the front panel menus are still fine. This one just seems to be kicking up a fuss. I agree with the idea that a prom holds data for multiple models, it's just a case of finding it as we have no service manuals for them. The memory battery was dead when I got the unit so this may have caused data to be wiped and it defaulted to a different set of data? I've tried re-uploading the firmware which is available on the website, this does nothing.

Another issue which has just presented its self... The voltage ranges are out of spec. I've adjusted them about three times now but they keep drifting out again. I verify that the adjustment has been successful directly after doing it and I get spot-on readings, but after a day or so they are out again. Even with the new battery in, which should  allow it to store data. It's storing things like IEEE address changes so it seems more like voltage drift than loss of data...