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Printer's gone again - thoughts please!

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throbscottle

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The Konica-Minolta 2530dl has finally settled down to a consistent fault - very faint, barely perceptible prints.

This is after going through single colour prints, half pages, usually with a thick speckled line across edge to edge where the printing finishes, a few pages then blank, pages with one colour missing, and occasional un-fused prints - though I think that may be user error. Very erratic mix of faults, often affected by turning the printer off and on, and by jiggling all the cartridges.

I've pretty much ruled out mechanical faults and drum (which I replaced), and it seems to have enough toner, though it's dropping it like mad, which leaves the EHT board and control board, PSU, or the laser module. Seems unlikely but I can't rule out the toner cartridges.

I guess I can use a photo transistor to detect laser output, which I believe is infra-red.

I have long suspected the EHT board to be flakey since I emptied the old drum cartridge, didn't put it back together right and caused big fat purple sparks, though a printer engineer did tell me they tend to fail outright, not develop a low output. He helped me decide it's probably not the transfer belt.

I find it mysterious that there is so much dropped toner. It is as if it is leaving the cartridge rollers and not making it to the paper, either getting dropped off the drum, or not getting as far as the drum - which to my mind suggests an EHT fault. I did try opening the printer at various points in the print cycle, not been able to observe any image on the drum or reverse images on the toner rollers.

Trouble is I reckon a faulty controller board could produce the same errors, especially having been so chaotic. How the heck do work out which?

So is it worth me replacing the EHT transformer driver transistors? Or am on a red herring here? There are no visible high voltage rectifiers, so I'm guessing they're potted in the transformers. Swapping the board isn't an option, replacing the transformers is also unlikely to be an option.

Replacing the printer isn't an option - it was free, I have no money to buy one, and even if I did I couldn't justify the purchase.

Help!
 
It sounds like your EHT connections are either dodgy somewhere, or the EHT block itself is faulty. I don't think it's a Laser issue or any of the syscon :)
 
Well at least that's the easiest bit to deal with then! It's been taken out and reconnected a few times, so I more likely to be a component fault or even a dry joint I think. I should try the old tappy-tappy whilst it's running - only just thought of that!

Thanks :)
 
Often they have a thin wire for charging the drum and these need cleaning periodically (corona wire). Also check the window of the laser assembly is clean and toner free.
 
Hiya picbits
Charging corotron is built into the drum cartridge, which is new, and laser window has been cleaned. Whole thing has been in pieces to eliminate mechanical faults, gave everything a good clean then :)
 
Yay, I think (I hope) I've fixed it. Just hope I'm not speaking too soon, "fixing it" has happened before...

Anyways, I thought I would delve into the EHT board and test the power transistors, and go from there. Pretty quickly found a 2SB1417 which appeared to have an open emitter. Pulled it, tested again to make sure... Nope, out of circuit it tested fine. Soldered it back in, tested fine again. I checked all the other semiconductors on the board whilst I was at it - all fine. Put the board in the printer, cleaned out all the dropped toner... test print... Yay! Shiny Red Car means it works!

So, in what I hope is the conclusion to a fault that has been troubling me for over a year now, a dry joint in this circuit would have produced the erratic and intermittent and apparently temperature sensitive fault I've been seeing.

If you hear a scream, you'll know it's doing it again though...
 
Yay, I think (I hope) I've fixed it. Just hope I'm not speaking too soon, "fixing it" has happened before...

Anyways, I thought I would delve into the EHT board and test the power transistors, and go from there. Pretty quickly found a 2SB1417 which appeared to have an open emitter. Pulled it, tested again to make sure... Nope, out of circuit it tested fine. Soldered it back in, tested fine again. I checked all the other semiconductors on the board whilst I was at it - all fine. Put the board in the printer, cleaned out all the dropped toner... test print... Yay! Shiny Red Car means it works!

So, in what I hope is the conclusion to a fault that has been troubling me for over a year now, a dry joint in this circuit would have produced the erratic and intermittent and apparently temperature sensitive fault I've been seeing.

If you hear a scream, you'll know it's doing it again though...

i HATE those dry joint related faults, circuit itself works fine but then, aw maan :S...
 
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