Lexmark C925 - Power shuts off automatically after 5 seconds

[907tec]

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.

[Phil B.]

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...
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.

did you happen to check continuity on the HARNESSES to make sure the wires weren't broken or pinched to the metal frame?

a lazy tech ( not you ) in a rush to put the covers back on can/do cut/damage the wires so from the output of the LVPS you can have proper voltage but not at the device that the wire goes to. As my eyes started going the last few years I started carry a magnifier glass in my bag to properly inspect the harnesses.

Just a thought

[907tec]

Sorry, I kinda glossed over that part. While checking the LVPS yesterday, I started by checking for continuity from the lvps connectors to the connectors on the other end. Then I checked from each pin on the lvps connector to the other destination pins looking for crossed/shorted wires in the same loom. Then I checked each LVPS line for short-to-ground. On larger connectors I usually jam the multimeter probe into the back of the connector and for smaller wires I just press into the vampire connections.

[FrohnB]

From the Manual I have; 121.05 = Fuser Heater Error.
If replacing the Fuser/ LVPS/ Printhead Control Board doesn't do the trick, and making sure all connections are seated doesn't work, it states that you should replace the "Fuser Power Cable".

[907tec]

From the Manual I have; 121.05 = Fuser Heater Error.
If replacing the Fuser/ LVPS/ Printhead Control Board doesn't do the trick, and making sure all connections are seated doesn't work, it states that you should replace the "Fuser Power Cable".

I'll take another look at the "fuser power cable", but it has passed every test I've thrown at it so far. I actually have it completely removed from the machine right now, just to confirm it wasn't pinched or anything. Appears to be making good contact and not grounded out anywhere. Doubt I can find another wiring harness anymore, but I suppose I could just make my own as it's only 4 wires from the LVPS to the fuser heating elements.

[blackcat4866]

Is it a 220v fuser installed into a 120v machine. I've seen similar symptom from that. =^..^=

[907tec]

Is it a 220v fuser installed into a 120v machine. I've seen similar symptom from that. =^..^=

Don't believe that's the case. Started happening out of the blue with their original fuser. I will double check the one I ordered, but it was certainly listed at 110v

[zenkinsw]

If fuser/LVPS/Printhead board done without help and pretty sure those parts number are the correct, clean and inspect the fuser connectors and see how you go.

From my previous job most of them are cause by faulty printhead controller board after user's site having power surge.

[dalewb74]

here at our office we have 2 words for the lexmark c925 models.

TARGET PRACTICE

we have had nothing but issues since they were put into the field. though i have one customer (last customer with this model) who is like yours. he has had no issues with his, other then replacing supplies. and he swears by this machine. good luck with the problem.