Timing on the paper feed assembly (Konica 7145 copier)

[eurosears]

I recently acquired a Minolta 7145 copier. When I first turned it on the copier after each page that ran through the copier would jam (J11, J12, J13, etc). Each tray and the bypass was behaving same way. After cleaning the paper tray gear systems, removing and checking the drum and developer now it appears that I have short somewhere and my Paper Feed Clutch/Motor (26NA82020) doesn't get enough voltage. It gets about 3V instead of 24V. Did anyone have ever had a problem like this, and if so how did you deal with it? Once you found the short did you have to replace the CB board or any other components?

[copytechman]

That depends on what's taking out the cb. Typically a pinched/shorted to frame wire will do that pretty consistently. The newer series machine (bh420/500) had an issue where if the wrong screw was reinstalled in the toner solenoid it would take out the cb cuz it shorted the solenoid to frame (via a cut coil wire).. could be something like that since you stated you had the drive system apart.. i'd check your wiring..

Regards!
A.

[eurosears]

I checked the voltage on the cable that leads to Loop Clutch (MC2) and it was 20V when the printer was idle and went to 24V when the printer wanted to take paper from the tray. At 24V the clutch engaged and the white gear was driving the clutch shaft which indicates to me everything is fine (I did this while holding the clutch in my hand). I also checked the gear in the copier that drives the white gear on the MC2 clutch. It started working when the copier was trying to pull paper from the tray.

I put the clutch back and observed that when the copier was trying to pull paper the paper tray gear assembly slightly moved and the jam occurred. So it looks like the clutch is ok.

I don't know whats wrong. All my trays, including the bypass, jam without even feeding the paper into the system (J11, J12, J13, etc). Could there be a problem with the drum? Any suggestions where I should concentrate my search?

There was a situation once where after putting all the paper tray assembly gears back together and running the copier I was able to run 5 copies without a problem before the printer started jamming again.

I also used the drum code in menu 47 to check if the drum is rotating and it was. It did remove the drum and the developer before (when I had a different jamming problem) to clean them. After putting them back in the drum/developer doesn't print any pictures(this is before the most recent jamming problem) and I have to do L detect each time I start the printer or get a jam - I know I will have to change the developer. Any suggestions?

[copytechman]

You may have a failed motor (or dev coupling) thats causing a mis code.... I've seen these throw jam codes before motor failure codes... that is to say it seems to time out on a jam before noticing that a/the motor isnt rotating.. Just a thought... mark your dev, put a void in the mag brush (with your finger or something to make a visible gap), run the ldetect or make a copy, pull the dev unit.. did it rotate? Could be a failed icp on a the cb but you said you checked them out.

Regards!
A.

[eurosears]

The dev was not the problem. Checked it like you suggested and it does move. However, I found one problem already the by pass paper feed system is not operating properly? Possibly a gear or two are bad. So I disconnected the white gear that is driven by the paper feed system and that drives the bypass tray and the papers started coming into and out of the printer from tray 1
The timing is all screwed up, however. If I make one copy the page gets stuck before the drum. If I make 10 pages, something like 10 come out with 2 being stuck at point 6-7 and point 3 or so (means two pages are in the system while the cycle of 10 has completed). Paper from tray two still gets stuck near the tray and can't pass through the system without a jam no matter what I do.
A person told me that the copier was dropped or hit while carrying it so this could explain the bypass tray problem. However, what to do about the paper feed timing. Any ideas?

[copytechman]

Thats's a tough one, timing issue in general could be failing/failed/sticky clutches or poor paper drive motor, have seen the primary paper supply clutch slip as well. I'd probably start by cleaning/replacing clutches if in general they are working but not perfectly... have also seen worn tray tires cause lots of issues too..

Regards!
A.

[eurosears]

Hey copytech I got that problem fixed but now I have another question. Is it true that you have to use non-magnetic screws to secure the TDS sensor to the developing unit? Is so, what is the part number for these screws? Thank you.

[copytechman]

Well thats a good question, i've not actually heard of that before and honestly never used anything other than a standard screw to attach to the dv box, according to my parts catalog it appears to be a standard screw, plastic type, it's used all over the place in the machine... fuser, dv, charger etc etc. I don't think its an aluminum screw based on my experience.

Regards!
A.

[eurosears]

Well thats a good question, i've not actually heard of that before and honestly never used anything other than a standard screw to attach to the dv box, according to my parts catalog it appears to be a standard screw, plastic type, it's used all over the place in the machine... fuser, dv, charger etc etc. I don't think its an aluminum screw based on my experience.

Regards!
A.

Hmmm, I had metal ones (regular steel), I wonder where I can get two plastic screws like that. Or maybe do you have two that you could spare? I can't install my new sensor and developer without them

[copytechman]

By plastic screw I'm referring to the thread type not the composition. You know, screws that you'd use to screw into plastic bits as opposed to metal bits. (Plastic screws have a real coarse thread while metal ones have a fine thread). If you've ever had the charger grid off and looked under the black cover that protects the corona wire ends, the end that is screwed down through a silver plate that routes to the hv contact on the back of the machine is a plastic screw, its the same one by my book... they're all over the place.. standard plastic coarse thread screw. Another example is: the screws that hold one the paper trays to it's tray rails is a metal screw. A type of plastic screw would be one of the screws that hold the front of the tray cover onto the trays (bigger diameter tho).

Regards.
A.

Seriously you should be able to find these all over the place.. old copiers probably have oodles... basically used to hold 2 plastic bits together or a metal bit onto a plastic bit.. etc etc.