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hazartilirot
08-20-2016, 08:55 AM
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
08-20-2016, 09:26 AM
Grab a meter and wiring diagram. Start of the power supply all the way to control panel.

Byting on bits.

hazartilirot
08-20-2016, 09:30 AM
Thank you for your response. I haven't got wiring diagrams. :( Could you tell me where I can download them on the Internet?

EarthKmTech
08-20-2016, 10:12 AM
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
08-20-2016, 10:25 AM
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
08-20-2016, 01:15 PM
they are in the end of the service manual.
here ya go anyway..

hazartilirot
08-20-2016, 01:41 PM
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
08-20-2016, 10:20 PM
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
08-21-2016, 12:40 AM
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
08-21-2016, 07:17 AM
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.

3390533906

hazartilirot
08-21-2016, 10:24 AM
Thanks mate for you suggestions. I was thinking the same. However, I'm going to take multimetre and do continuity test between two plugs: UN201 and PWB-C boards. For no apparent reason I think the problem lies on a flexible cable.

BTW: can anyone share a genuine service manual including wiring diagrams? The diagrams shared by Synthohol are more likely printed in raster graphic. :( Most pinouts turned out to be illegible. :(

33907

EarthKmTech
08-21-2016, 10:31 AM
all you need is +5V and 2 negatives.

+5v is the line running to the onboard fuse on the inverter board

one of the negatives is negative power the other is activate. The activate pin will floating above 0V on it at idle to be clamped to 0V if you want to add a switch to turn it on and off.

This is a crusty old DI2510 panel i had on hand.

It does draw about half an amp so be careful where you get your 5v from, preferably as close to the input ribbon cable as possible, if it has a 5V supply which presumably it does.

3390833909

There is filtering in between the + and - going to the inverter and the rest of the panel, i suspect the inverter will be noisy on its supply. If you find the panel logic locking up or behaving erratically you may have to fix the machine properly.

OR

You could just run it off an external 5v 750mA wall wart, Or regulated USB charger capable of 1 amp.

On this DI2510 panel, pin 1 is negative, pin 2 is activate, floats at 1.5v clamp to ground to enable backlight and pin3 is +5v. I cant say the c250 would be the same but it wouldn't surprise me.

hazartilirot
08-23-2016, 10:38 PM
Good day to everybody.

Here's my latest news. The printer is driving me mad. I've already replaced:

- PU
- PWB-M
- PWB-SIF
- PWB-C
- UN201

The only thing left is PWB-MFP. Backlights in two control panels are still not working! However, I've found an owner of the same printer's model in my city today and checked two panels on her printer. Everything works perfectly well!

Can the issue somehow relate to the printer's firmware or inoperative MFP board? Could a previous owner have turned the backlight off in the service menu? Should I reset the printer settings to the factory default or is it better to upgrade its firmware?
Can my flexible cable connected to UN201 be the hindrance? Should I try to connect it the other way round?


BTW I've found a thread in the forum.... his problem sounds just like mine. I wonder how he has solved the issue. :(
http://www.copytechnet.com/forums/konica-minolta/26881-konica-bizhub-c250-screen-problem.html

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