Printer and Photocopier Troubleshooting and Repair Collection : Canon PC25 copier problems              
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Canon PC25 copier problems

"The lamps goes on my Canon PC-25 but I get nothing but black copiers. I'm told the problem could be a broken corona wire. Where is the corona wire located? What does it look like? How do I determine if it's broken and how is it replaced? Thanks in advance."

(From: Lionel Wagner (ck508@FreeNet.Carleton.CA).)

I doubt the cause is a broken corona wire. If this were the case you would get white copies, instead of black. Check the bias lamps are coming on. They are a string of small lamps located 'downstream' from the transfer corona (located at the bottom of the drum).

"I have an elderly Canon PC25 Copier, which still runs well apart from two problems.

The first is an intermittent fault which makes it turn out blank paper, usually on switching on but occasionally during a run. I assume this is a faulty joint on a circuit board because opening the machine and slamming the top down usually cures it for the moment.

The second is that the light/dark slider has to be at one end of its range to get satisfactory copies.

Are these common faults on this model with a recognized cure? Although it is expensive to run, I seldom need enough copies to justify purchasing a new one."

(From: Lionel Wagner (ck508@FreeNet.Carleton.CA).)

You're right about the bad connection fixed by the vibration of closing the cover. Your exposure control is probably at darker than normal to compensate for aging of the photo-sensitive drum. Some compensation is possible by adjusting the high voltage or (I prefer) the toner wheel bias voltage. I'm assuming your corona wires are clean, of course.

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