Minolta Di-450, uneven copies.

[Hansoon]

Minolta Di-450, uneven copies.

Machine has 350K on the clock. Developer 350K, Drum 70K. Copies are uneven from rear to front across feeding direction. See F12-3 Testpattern with inserted piece of testpattern of a healthy machine for comparison.



Tried until now: New corona's and a new drum and played with settings but only minor improvement, cleaned slit glass and discharge lamps ofcourse before. Bias connection seems to be OK but no opportunity to measure yet.

Values are as follows:

Vg -4
Density +3
LD1 current 95, LD1 set 83
LD2 current 94, LD2 set 79

I have to go there Monday morning and will try as a last solution to exchange the laser unit. Any experience with a fogged laserpath in this machine? Any other suggestions please?

Hans

[minimerlin]

What does the brush height look like? Also I think that if you have got a Vg set to -4 then there is a problem somewhere. I seem to remember a problem caused by the bad alignment of the drum drive, has it had the spacers fitted at the back? I also think it is not a good idea to change drum but not the dev! I would fit new dev and also clean the bias connector pin and its socket at the rear machine frame..remove the black conductive grease!

[cobiray]

IIRC the developer is only good for 200k, not to mention it's probably at least 6 years old at this point and has lost some or most of it's triboelectic properties. I'd start with the developer first before tinkering with any more settings. Also, I'd put the settings you've changed back to the default settings. You mentioned coronas, so I assume you replaced both the transfer and sep coronas. If not, replace those and clean out the housing.

[Hansoon]

Before cleaning or replacing the laser unit I tried another developing unit which took care for the problem for the moment. However, without having time right now to investigate matters more deeply, I do not believe that this is the only reason for the uneven copies but I accept the "solution" for the moment cause I couldn't allow more downtime at this customer.

Thanks for your input gentlemen.

Hans

[brent]

for what it's worth. I would think that going to the extreme of changing out a laser unit would be out of the question. you seem to have a good sense of technical ability. why not just change out the developer and see how it goes? I had one like this that I thought I had to do the whole shim thing. and it turns out that all I needed to do was replace a developer and run the f8. by swapping out the whole dv unit you only probably bought some time. did it have newer developer? old developer? now the counters are all off. plus your atdc level is wrong. the proper way is new developer then you run your f8 that sets up your atdc reference voltage. that is how the copier keeps the right amount of toner to carrier ratio.. you might even get light copies again because the machine is set at a certain level, and when it gets to a point you may find yourself back there again. keep that old dv unit.. replace developer... just a thought

brent

[Hansoon]

Thanks for that interesting input Brent. The reason why I am hesitating that only developer would be the reason is that there's a pattern in the "unevenness" from rear to front which I cannot explain except a fogged laser path or perhaps a warped doctor blade. Furthermore do I have several Di-450/550's making over 500K with the same charge of developer. The machine starts counting from zero again when the starter counter goes over 500K. Copies are still good surprisingly.

Hans

[brent]

I agree that sometimes you can get more out of the yield. is the machine level?

brent

[Hansoon]

I agree that sometimes you can get more out of the yield. is the machine level?

brent

No, its tilted slightly towards the rear. That's interesting, I just did notice that yesterday but somehow was so occupied that it didn't sink in at the time However there was an unsatisfying feeling inside of me that I had to check something and now you reminded me.... Thanks.

Hans

[brent]

level the machine. then take the dv unit out and manually level it. then run another copy. although I wold still replace developer. I would bet that there is very little developer in the unit. but being uneven will definitly do this also. I had one that was not level and I never thought anything about it. 20 k later it all spilled out the rear. we might be onto something here

brent

[dcopylady]

light copies

I agree with brent - there is likely not much developer left inside. Take out the imaging unit, remove the drum and rotate the developer drive by hand to see what kind of coverage there is on the mag roller. If in fact it 'looks thin', change it, and clean the grounding pin on the rear of the imaging unit and in the back of the machine. Something is sucking out the developer - almost always a poor connection or ground.
Good Luck,
dcopylady

[minimerlin]

I agree with brent - there is likely not much developer left inside. Take out the imaging unit, remove the drum and rotate the developer drive by hand to see what kind of coverage there is on the mag roller. If in fact it 'looks thin', change it, and clean the grounding pin on the rear of the imaging unit and in the back of the machine. Something is sucking out the developer - almost always a poor connection or ground.
Good Luck,
dcopylady

I seem to remember suggesting these actions 6 days ago!

[Guest]

starter no doubt about.(thats developer for you new guys)