Adventures with EPROMsFebruary 16th, 2012 by Jeff
In December I received a strange request from Franci, S57FK. He had a sick Fluke 8842A digital multimeter with a bad processor and was in desperate need of some EPROM images. He noticed that I had an identical Fluke sitting on my bench and was hoping that I could read the contents of the EPROMs inside my unit and send them to him so that he could get his meter running again.
I said sure, but I had a problem – I didn’t own an EPROM programmer.
Well, I had been looking for an excuse to buy one for a while, so I went on eBay and bought one of the cheapest EPROM programmers I could find (for $15).
The programmer, which is a Willem clone, arrived some weeks later:
As an aside, the Fluke 8842A uses a weird Z80 processor with stacked external EPROM storage (I think EMSL has shown pictures of these in the past):
The next problem I ran into was that the “old” (circa 2004) Windows XP laptop I use in the lab didn’t have a parallel port, so I had to find a way to run the klunky old Willem software on my new desktop PC, which runs Windows 7 64-bit (but surprisingly does have a parallel port). The Willem software is written for Windows XP and won’t run on Windows 7, at least not the 64-bit version.
Thanks to this tutorial I was able to replace the io.dll that comes with the Willem software with a new one that works with Windows 7 64-bit. I was shocked at how easy this was (and that it worked at all), but 10 minutes later I was able to launch the Willem software without errors:
Actually reading the EPROMs was pretty simple:
- Remove EPROMs U202B and U222 from the Fluke 8842A (U222 required some work to dig it out, it’s located under the AC line EMI suppressor)
- Connect Willem programmer to PC (parallel and USB ports) and launch EPROM50 software.
- Select EPROM type through the Device menu (2732 in this case)
- Adjust the DIP switch and jumper settings on the programmer to match the diagrams in the software. I had to move one jumper from the factory position and change a few of the DIP switches.
- Insert one EPROM at a time into the ZIF socket on the programmer, following the diagram shown in the software to align the chip.
- Click the Read Chip button (the one with the green arrow) and specify a file, click OK.
It is probably a good idea to look at the contents of the resulting BIN files to make sure they aren’t all zeroes (that happened to me once) and contain something that looks like valid data. You’ll need a hex editor for this. I used HxD.
I sent the files to Franci, and he was able to get his meter working again. Success!
I was a little bit nervous to put everything back together again, fearing that I might have accidentally ‘zapped’ one of the EPROMs while I was learning how to use the programmer. Fortunately, the meter still works just fine: