KM-4800w No Display

monstott2010 · 11-23-2015

Originally Posted by subaro

I am saying up front i do not work on this machine, but looking at the thread and seeing you description of the problem, i would think it is more of something not sitting properly or some connector moved out of place. You replaced motherboard, hard drive and power supply already.
I downloaded the service manual for the 4850 and not sure how close this is to the 4800. but i would unplug the unnecessary connectors that is comming from the mother board and hook up the external monitor and power on and see. aslo check all the door switches to make sure they are working. unplug the internal monitor and scanner connection from the motherboard also.
There is also a pc control pcb that supplys voltage to the internal monitor, and other signals that i guess controls the motherboard. therefore with voltage going to the monitor you would get backlight, but data comes from the motherboard which something there is either shorting out, not connected or bad. there are two switches that goes to that pc control pwb, the fuser sw and another upper int sw, check if those are working when closed.

Thanks for the reply.. I currently have the print controller at the office, out of the machine. All of the MACHINE side limitations/possible issues are at this point voided... I have the controller connected to a standard PC monitor using a RGB connector. When powering on (plugging in) the controller, the power supply and PCU fan both power up and LEDs on the motherboard and PCI board all light normal... visually, the system would appear to be "on" and in a ready state, however, still not getting any display to the monitor. Monitor does detect if connection removed so assuming at least part of the connection is normal... seems so basic, not sure why this thing will not boot up

Just put the old motherboard back in, thinking since the HDD/Software was the suspect, old board should be ok - still no display -

**subaro** · 11-23-2015

now getting an idea what's going on. In this case, you don't have any short, but either your pci card is bad or the memory chip. again i have never seen this, so i don't know the configuration here. remove the memory chip or chips and examine the slots where the memory is inserted carefully with a flashlight and a magnifier or any abnormal pins. you can also try pushing the chips a bit firm one way a bit firm while powering up and the other way. this is common on desktop pcs, not saying this is the solution here, but something to try. did you try another pci video card, even though the light is working. Only other thing here, is what is booting the system, the hard drive or is there a bios chip to start the system and then the hard drive kicks in with the rest of the software, somewhat like desktop computer. A move should not affect any bios chips, only the hard drive which has moving parts, unless it [ bios chip ]was erased by failed f/w update or something like that . what about the memory chips if they are replaceable , did you replace them.
Hope you get this working and let us know when you solve it.

monstott2010 · 11-24-2015

Thanks for all the help, FINALLY got the machine back up and running...

Was advised of a pin group (9 pins) on the motherboard that needed to be shorted across to force a reset - and it brought the video back up... jumped the 9 pins, powered on, got a post beep (that was not heard before) and the fans went to a lower speed. Turned the system back off, removed the jumper and pwr back on again, powered completely up and system came up to normal operating display. Attaching the picture sent to me, my board was slightly different, but was able to locate the correct pin set.

Reset Jumper - after power supply failure.jpg

**subaro** · 11-25-2015

Nice you got it working. those type of jumper for resets brings me back to the days when repairing laptops had those issues. manufactures had special jumper points to reset motherboards ect. trade secrets, so you had to come to their repair depot.

**aspenhyd** · 05-27-2021

Hi all, Reviving this old thread because we have the same machine and we think we have the same issue, just wondering if anyone else has had success with the method described by monstott2010?

Was advised of a pin group (9 pins) on the motherboard that needed to be shorted across to force a reset - and it brought the video back up... jumped the 9 pins, powered on, got a post beep (that was not heard before) and the fans went to a lower speed. Turned the system back off, removed the jumper and pwr back on again, powered completely up and system came up to normal operating display. Attaching the picture sent to me, my board was slightly different, but was able to locate the correct pin set.

Hoping to get some more thorough instructions if at all possible

thanks for any replies!

**Phil B.** · 05-27-2021

Originally Posted by aspenhyd

Hi all, Reviving this old thread because we have the same machine and we think we have the same issue, just wondering if anyone else has had success with the method described by monstott2010?

Hoping to get some more thorough instructions if at all possible

thanks for any replies!

that was over 6 years ago

start your own new thread listing all problems and what you have tried.... one commentator was a guest doubt he is even still
here