I have the misfortune of working on this (seemingly) obscure old printer. Original call was for power shutting off automatically, five seconds after turning the machine on. This is apparently common in Lexmark-land, and the service manual even has a specific section regarding the issue. They make it sound like it's so cut-and-dried: Replace Fuser, LVPS, and Printhead Control Board. I have to emphasize at this point how much time I spent trying to talk this customer out of spending money on this machine. I told them straight up that there were no guarantees about these parts working, and that it wasn't advisable. They must really like the machine, because they approved repairs anyways.
Before ordering anything, I already did the free stuff: check/clean/reseat all connections, attempt starting the machine with various/all consumables removed, etc. Found that when I removed the fuser from the machine, it would boot fully before giving error 121.05. Manual states "if the error is 121.05 the fuser is at end of life". Simple, right? Replace the fuser. No change in behavior. Ok, well the next most obvious in my mind (and prescribed in the 121.05 error steps) is the LVPS. Also no change. Next (and final) step in the manual is the Printhead Controller Board. You guessed it, no change. Despite how much I railed against the customer spending this money, I still feel bad to walk away defeated. So now I have the thing in pieces on my desk.
The service manual is seriously lacking in detail, especially when it comes to the wiring diagram/pin-outs. With that being said, I have checked all the LVPS outputs and they appear to be good. No crossed wires, no ground faults, all good continuity. Completely removed the fusing circuit from the machine to check for pinches/etc and confirm solid connection to the fuser. Removed all consumables and began removing connections from boards one at a time. Thought I had a discovery at first, but I just unplugged the connector for the solenoid that trips the power switch...
Machine will not trip the power switch if the signal/sensor wires are disconnected from the fuser circuit.
I'm starting to suspect that this really is related to the new fuser not resetting the life counter, but there is no way to tell. I can't boot into the 2-6 or 3-6 modes. I have taken apart one of the fusers and can't find any signs of a reset fuse to try replacing, either. Customer updated firmware in 2019 (supposedly) and latest FW from Lexmark was in 2018, and there were no mentions in the release notes for anything like this, even if I could install it.
So, I am really, really hoping that someone on here will tell me I'm an idiot and that I've overlooked something simple. I'd rather hear that than give up on this pos.
Before ordering anything, I already did the free stuff: check/clean/reseat all connections, attempt starting the machine with various/all consumables removed, etc. Found that when I removed the fuser from the machine, it would boot fully before giving error 121.05. Manual states "if the error is 121.05 the fuser is at end of life". Simple, right? Replace the fuser. No change in behavior. Ok, well the next most obvious in my mind (and prescribed in the 121.05 error steps) is the LVPS. Also no change. Next (and final) step in the manual is the Printhead Controller Board. You guessed it, no change. Despite how much I railed against the customer spending this money, I still feel bad to walk away defeated. So now I have the thing in pieces on my desk.
The service manual is seriously lacking in detail, especially when it comes to the wiring diagram/pin-outs. With that being said, I have checked all the LVPS outputs and they appear to be good. No crossed wires, no ground faults, all good continuity. Completely removed the fusing circuit from the machine to check for pinches/etc and confirm solid connection to the fuser. Removed all consumables and began removing connections from boards one at a time. Thought I had a discovery at first, but I just unplugged the connector for the solenoid that trips the power switch...
Machine will not trip the power switch if the signal/sensor wires are disconnected from the fuser circuit.
I'm starting to suspect that this really is related to the new fuser not resetting the life counter, but there is no way to tell. I can't boot into the 2-6 or 3-6 modes. I have taken apart one of the fusers and can't find any signs of a reset fuse to try replacing, either. Customer updated firmware in 2019 (supposedly) and latest FW from Lexmark was in 2018, and there were no mentions in the release notes for anything like this, even if I could install it.
So, I am really, really hoping that someone on here will tell me I'm an idiot and that I've overlooked something simple. I'd rather hear that than give up on this pos.
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