Konica Minolta C252 - a backlit LCD screen malfunctions

[hazartilirot]

Good day!

We've recently bought a Konica Minolta C252.
The issue it had was relating to a touchscreen. That's what we were told before buying the printer. It didn't respond. Taking out our control panel from the old printer I've changed the native panel to it. It works perfectly! Now, I'm able to interact with the interface, all green LEDs are lit. However, I cannot work out why the backlight doesn't work. It doesn't matter what control panel I connect to the printer.

I've got our old printer which is the same model therefore I'm going to change PCBs one by one to work out what's the hindrance although I would appreciate any suggestion made by the dear community as to what part of the printer should I begin with? The very first thing I think I should begin with is Power Unit.

Please share your thoughts.....

[habik]

Grab a meter and wiring diagram. Start of the power supply all the way to control panel.

Byting on bits.

[hazartilirot]

Thank you for your response. I haven't got wiring diagrams. Could you tell me where I can download them on the Internet?

[EarthKmTech]

I seem to recall an IC on the PWB-M going thermonuclear causing this.

If you try the board from another machine remember to swap over the 8 pin eeprom, the one from the machine needs to stay with the machine.

[hazartilirot]

Yes, I know it. It's also written in the service manual. Thank you. However, is there a way to download somewhere on the Internet the wiring diagrams of C252? I've got a voltmetre so I'm interested in those diagrams.

[Synthohol]

they are in the end of the service manual.
here ya go anyway..

[hazartilirot]

they are in the end of the service manual.
here ya go anyway..

Wow, thanks! BTW I don't have this part of the serivce manual I've found on the Internet! How strange it is.... Hm.....

[hazartilirot]

Well, today was a fruitless day.... I've changed PWB-M and PU1 boards.... I hoped that it would resolve the issue with LCD backlight, however all my efforts were in vain.

To my mind the next thing I'm going to change would be a PWB-C board.

Any thoughts?

[EarthKmTech]

are you sure the backlight is ok ?

have you tested for voltage on the primary side of the inverter board ?

If i remember correctly it has power and pwm signal for intensity / activation. If there is power you could jumper the intensity pin to either ground or 5v for full brightness (cant remember) It will however never turn off and eventually burn out the fluorescent tube.

i am assuming you are aware of the danger of screwing around with an inverter board and the high secondary voltage and the risks involved if you have conditions that might see you dead from such an electric shock.

[hazartilirot]

The last time I checked our old control panel it was ok though the native backlight in the new printer doesn't work either. I'll test for voltage on monday.

The thing about our old C252 is I cannot re-check control panels since a flexible cable has become inoperative.

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