Xerox Phaser 7500 NVRAM issue

[Guest]

Hello All!

Gots me a Xerox problem and hope someone can help!

The low down...
This machine had the MCU board replaced a little while ago, and one of my techs ended up bending the EEPROM legs and breaking one off. We just replaced the EEPROM and the machine now boots but I'm getting the following errors. 61-358 and 41-340. The main is the 61-358 as the other has only shown up once.

Looks like it is not recognizing the yellow laser as being compatible with this machine, there is also a different error on the web interface that shows it is the wrong Transfer Belt installed.

So I'm figuring something went wrong when the EEPROM was written to and now the machine doesn't know what model it is as these parts were not replaced and had been working fine before the MCU was replaced.

I want to reset the NVRAM but looks like the full reset is in the hidden menu which is inaccessable due to the error that comes up after POST. Diagnostics menu has some NVRAM options but none of what I need.

I also can't update the firmware as I can't get it into a print ready state.

SO! Is there a special power up sequence that will put the machine into a flash ready mode? Or is there another way to reset the NVRAM that I have not been able to find? Like maybe a jumper on the MCU or a power up sequence?

Thanks guys!

- Wes

[asturkinos1]

Hello!

Amazingly enough, I have been fighting with a similar issue since around the time you posted your message here. I've had this old Phaser 7500 for several years with no issue whatsoever. i got the machine pretty old and with heavy meters, expecting it not to last very long.

I did some research on supplies, chips and the like (I come from a good old Phaser 6125) and I have been collecting some spare parts, including Image Processor Board, hard disk and others.

Then, a couple of weeks ago I got one of those "Belt Home Took Too Long" errors and I thought it was going to be easy to fix, just a good cleanup and ready to go. But it turned out to be much worse than that. After days trying to debug, removing the IBT, the MOB ADC assembly and whatnot I ended up with your infamous 041-340. In my case I got the error after clearing tech rep fauts on the service menu; the second time I did it I got a FAILED message and for the next boot I was greeted with "Engine Failure".

Fast-forward a couple of weeks and I have to admit I haven't progressed very far. I have been doing some research that I can share with you, maybe it'll help you somehow.

First useful thing to know about this machine is the serial port debug (back channel traces, they call it in the manual). To get those you need a serial port on your computer, a USB to serial seems the most convenient but you can also use a Raspberry Pi or anything like that. The detailed wiring is not in the manual (they only explain how to connect their own Xerox thing), but I can give you all the details if you want to give it a try. Once you have access to those messages you will probably see something similar to what I have: MCU EEPROM Failure detected (0x050). And then some synchronization issues, something related to a spurious byte received.

Once I got that error I started messing with the EEPROM chips on the machine. There are two chips, a big 24LC256 on the I/P board from Microchip and a smaller 24C64 on the MCU. I extracted those from their sockets and dumped their contents to files. I am now trying to learn something useful from them. Both are showing HEX codes encoded in ASCII, with a memory map, something like this:

...
0040| 00 94 00 94 00 94 00 94 04 b2 04 b5 04 df 04 b2
0050| 04 b8 05 4c 05 22 04 b8 05 05 04 fc 04 f8 05 a0​
.... 

The I/P board chip has the serial number, IP address and some other useful things but I'm afraid it's going to be pretty difficult to reverse-engineer what is wrong.

I know for sure the one that is wrong is the one on the MCU and based on what I read around here and other machines' manuals I think there must be a way to force the machine to write the right data to a blank EEPROM but I still have no idea how to do that.

If you want to have more details on the serial port debug or the dumped files of my chips just ask. But I don't think those are going to help you, you are looking for the same process to write on a blank chip.

If you are patient enough I'm almost sure I will be able to fix my machine at some point. I have a second unit that I could use to debug hardware issues or get the contents of its EEPROM chips but right now I don't want to mess with that so I'm trying to find a cheap second-hand spare for the MCU board.

Obviously, as you say, the easiest thing to do in this case seems to try updating/rewriting the firmware. But so far I did not find a way. I did try to do it over USB with Xerox's downloader utility but nothing happened (I have to try that once again with the serial port debug to see what's going on in the background). I did not try the network server yet.

By the way, since we have the same error code I'm assuming something went wrong with the EEPROM on your MCU, am I right?

Other thing I want to try is replacing the EEPROM with blanks, but I did not receive spares yet. There is a way to initialize the NVRAM from the service menu, but at least with the damaged chip it did not fix my issues.

According to the manual, one of the partitions on the hard disk stores Backup data of Download Firmware, backup data of non-volatile data, that's something to take a look to.

Of course, there is also the possibility that the only way to fix a corrupted MCU EEPROM is to replace it with a functioning one or that this is a hardware issue of the MCU itself not related to the EEPROM, but at the moment I don't think that's the case.

Regards.