Laserjet M4345MFP problems

[Jeff M.]

Have an M4345, problems started with a 49 error. Replaced formatter, was fine for about 2 weeks, then screen went completely blank. No lights, no display. Only thing running was fan for DC controller, but could get an engine test with formatter removed. Replaced Formatter again. Nothing. Tried hard drive. Nothing. Put back original hard drive, replaced Power condition board and DC controller. Display came back but would not fully load program. Stopped loading at "D". If you left it on, eventually display would go blank. Replaced hard drive and finally worked. Tested and tested and worked great. So now I have replaced formatter (twice), hard drive, DC controller and power conditioning board. Machine sat over the weekend, and following Tuesday delivered back to customer. Plugged it in, nothing. Just DC contoller fan running. Pulled machine again, replaced engine control board. Display came back on, but very faint and with horizontal lines moving down the display. Still will not fully load program to operate machine, and now cannot get an engine test. Rechecked all connections to all boards, all good. Tried another power conditioning board, nothing. I'm thinking a bad DC controller or engine control board, but maybe I'm missing something. What a nightmare!!! Seems highly unlikely replacement DC controller or engine control are bad, but I'm out of ideas. Thanks for any help!!! Jeff M.

[JustManuals]

Re: Laserjet M4345MFP problems

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[prntrfxr]

Re: Laserjet M4345MFP problems

See if the problem goes away when you disconnect the hard drive (cable to formatter).

[Wild Bill]

[Jeff M.]

Re: Laserjet M4345MFP problems

Tried disconnecting hard drive, no change. Display is light, display has wavy lines like the old TVs that needed horizontal adjustment, will not finish loading program, so will not give any error codes. I'm still leaning toward the power supply. Ordering another one today, hoping for the best. Thanks..... Jeff M.

[ucinn]

Re: Laserjet M4345MFP problems

Tried disconnecting hard drive, no change. Display is light, display has wavy lines like the old TVs that needed horizontal adjustment, will not finish loading program, so will not give any error codes. I'm still leaning toward the power supply. Ordering another one today, hoping for the best. Thanks..... Jeff M.

Have you tried the engine power supply? I've had quite a few of these go bad which causes it not to load and no backlight.

[Tec1]

Re: Laserjet M4345MFP problems

i had a HP 4300 w/ no power up or if i remember screen lite up dimmly but no display.

was bad firmware

when you replace formatter you prob. had to put in old firmware card with new formatter.

hope that helps???

[Jeff M.]

Re: Laserjet M4345MFP problems

Firmware is embedded in formatter on the M4345, so nothing had to be exchanged. I've got another engine power supply on order, hopefully will be in tomorrow. Thanks...... Jeff M.

[Tec1]

Re: Laserjet M4345MFP problems

sorry M4345 - embeded
LJ4345 - removable

[Jeff M.]

Re: Laserjet M4345MFP problems

OK, I think I've finally got this fixed. Replaced the engine power supply again, and everything came to life. Had a defective one, obviously. Tried turning off and on 4 or 5 times, worked every time. Delivered to customer again, and sure as shootin', powered it on, lights came on, display came on, and nothing else......What the f#$%??? Reseated formatter, nothing. Reseated again, a little more agressively, and viola, it's working. Don't think it should be this touchy, but it's been 3 days, and still working. Had checked all connections numerous times as I was tearing it down, so I don't think it's that. What a friggin nightmare. Definitely not shy about tearing this model apart anymore.... Thanks to all for your input. Jeff M.

[ucinn]

Re: Laserjet M4345MFP problems

OK, I think I've finally got this fixed. Replaced the engine power supply again, and everything came to life. Had a defective one, obviously. Tried turning off and on 4 or 5 times, worked every time. Delivered to customer again, and sure as shootin', powered it on, lights came on, display came on, and nothing else......What the f#$%??? Reseated formatter, nothing. Reseated again, a little more agressively, and viola, it's working. Don't think it should be this touchy, but it's been 3 days, and still working. Had checked all connections numerous times as I was tearing it down, so I don't think it's that. What a friggin nightmare. Definitely not shy about tearing this model apart anymore.... Thanks to all for your input. Jeff M.

The electronics in these things are horrible. I sometimes have them stick on reboot at 4/6A and won't go any further after doing a maint. kit reset.. if that happens, I disconnect the hard drive, let it reboot all the way, then turn back off, reconnect the hard drive, and reboot with an initliaize disks and it usually comes back to life. These things hate to be turned off.. so do the 3035's and 9050's

[Bayonette80]

Re: Laserjet M4345MFP failure to start-up, and no display backlight - fixed!

I realize this is a very old thread, but it proved invaluable to me, so I wanted to weigh in with my gratitude - the engine power supply board did indeed resolve a start-up hang-up and dead display backlight that I was unable to resolve by any other means. Thank you.