Question about OKI B4350 Laser Printer

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Oki B4350 Error 020

As soon as the printer is turned on the screen reads ERROR020 and the printer will not do anything.



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SOURCE: Error 020 on OKI B4350 printer

After pushing the on button, RAM CHK- initializing-- on-line - auto, and then, over and over and over again. It just goes in a circle.Pardon my english. Denmark is calling :-)

Posted on Feb 15, 2010

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SOURCE: Error 020 on OKI B4350 printer

First thing I check on the Oki LED printers anymore is the capacitors on the power supply. There are 2 types of power supplies used on the B4350's and others in the B4xxx series - one works fine, the other is nearly always the cause of odd errors. Open the top by opening the toner door, remove the toner/drum assembly and set aside, remove the screw on the smaller back cover and set the cover aside (screw stays captive with the cover) then up near where the toner was there are two clips, one on each side, that hold the main cover down. Dont break them, just get them enough to release the cover from the chassis. Lift the front of the cover up, unhook the back then lift up and off and set aside. Now take a flashlight the rear and look through the fan and to the left of it (as you look at the back of the printer) and you should see some skinny cans with a shrink plastic covering and a strip of "-" marks running down one side. Those are electrolytic (aka can) capacitors. Look at the tops of the two taller ones near the fan and see if the tops are perfectly flat (they are good if they are flat) or if they are bulging up, or even have some brownish residue on top and bulged. This is the typical sign of failure of the Chinese made capacitors anymore. IF you do see swelled tops or leakage then this is your problem and you can either replace the power supply as a unit (quite expensive) or if you know how to replace the capacitors you can get them from an electronic supplier. I have to use Digikey myself. There are actually three capacitors that fail, all in a group. There is a 1500uF 10v, a 270uF 50V and a smaller 56 uF 50V in between them that will also show swelling despite it's small size. You should use the same microfarad value but you can go one range up in voltage - NEVER go below the rated voltage on the original capacitor. I use the exact capacitance (uF) and voltage as the power supply is pretty tight on space and if you go up in voltage the size usually goes up. Also they are polarized - make sure you get the dashes on the correct side when replacing or they will explode. Once replaced you can test with the cover off but with the toner back in and the toner door down. If all is fine then open it, put the main cover and small cover on and run it.

Alternately if you dont find bad capacitors you will need the service manual to troubleshoot the error condition. One place that sells PDF manuals is

Posted on Jun 30, 2010

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1 Answer

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Error 020 means its a problem with the main board(hardware) on the printer. you should contact printer manufacturer.

***If you need any technical help on printer then you can reach at

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Visit to the given link.
If the error code you're looking for is not in the table (in above link) then send an email to and we will find out what it means...

Hope this has helped you...

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After pushing the on button, RAM CHK- initializing-- on-line - auto, and then, over and over and over again. It just goes in a circle.Pardon my english. Denmark is calling :-)

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I just changed the toner and I now have an error code 020

020 is a CU rom error... check that your memory and PS cards are fitted into the main PCB properly, if not remove the PS card and try it. Beyond that you might have a faulty main board

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Hi there,

I had same problem and when I installed OKI B4350 (PCL) driver it started working fine.
Before I had OKI B4350(PS) driver installed and it gave me invalid data error everytime I've pressed print.
I hope this works for you too.

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This sounds like it could be a "toner Sense" error / try removing the drum unit and cleaning the 6 contacts on the left inside of the printer

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If it's under warranty, contact the seller or
call 1-800-OKIDATA

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