laserjet pro 200 MFP m276nw : 50.4 fuser error (changed fuser, hi and low psu, and dist board)

[dan-kof]

Have a laserjet pro 200 MFP M276nw with a 50.4 fuser error.

And due to having another  printer of same exact model  , was able to troubleshoot.

(no manual, but good with multimeter, osciloscope, and circuitry)

First issue seems that nether the fan nor main motor show any life during power up, only fuser motor runs ( on broken printer)

Unlike on the working one where , the fan, the main motor  and fuser motor all go trough their power on sequence.

Second noticeable issue is that HV from the  High voltage board does not even pulse for a second,

no click of the the HV relay (on broken printers HV board)

Unlike on the working one where i see a good ac spike for a second to the fuser, accompanied by a relay click.

And due to having another same exact model printer , i was able to troubleshoot by replacing  a single piece at the time.

First the fuser itself, then the HV supply board ( low side of the fuser relay on a working board measures half the resistance vs the bad one)

But is not the problem . same issues and error. no relay click out of the good board eather.

Then the main distribution board (RM1-8706)? Without success .

And lastly the Low volt power supply .

Exactly same power up  with lack of fan and main motor and same error.

With 4 of those things  from a working printer i am at a loss (besides assuming some broken wires)

EDIT: also tried changing RM1-9010 board  (same story)

So besides the 3boards : main motherboard(the big one) the comunication(wifi/usb/ethernet) and phone modem board ,

everything was swapped in from a working printer , without any changes in behavior, and same error.

Any other guesses would be very apreciated, as we like this model of printer and would like to keep them running.

dan

[Repairatrooper]

All fans are managed by the DC controller board which is the RM1-9010 board you changed out. What was the issue with the printer you have been taking parts from? If the other printer was dead, it is quite possible it had the same failed board. All fans should come on when power is first turned on.

[dan-kof]

Nothing was (is?) wrong with second printer (hope that did not change in the process 🙂

I just used its parts to try and figure out  of what was wrong with the printer that was showing 50.4

and not running the main motor or the fan.

Will keep them apart for few more days , if i cannot figure out what is wrong by then .

I might just try putting the broken printers  boards in to the working one first to see if they work.