Tray 3 horizontal transport jams

I have a Bizhub C654e with jamming in the tray 3 horizontal transport unit (J-1730). 

The C654e and C754e or their black and white counterparts have large capacity trays for the bottom two trays. Tray 3 can hold 1500 sheets of 80gsm and tray 4 1000. The trays are position side by side with tray 3 on the left so to get paper from tray 3 to the vertical feed path on the right of the machine a hozontal transport unit is fitted above tray 4. This is why tray 4 is smaller.

J-1730 jams in this horizontal transport unit are just the same as jams at the vertical feed and mean that while paper pick-up was good there was a problem with the paper feed or separation rollers. So first thing is to change the worn looking feed and separation rollers. Easy.

Still jamming.

When removing the jammed paper I can see that the paper has not yet entered the horizontal transport unit so the problem must be in the feed station. There are a set of horizontal feed rollers in the feed station itself so I pull the cover off to have a look but didn't find anything suspicious. While the cover was off I removed the feed sensor actuator to have a look to see if the sensor was dusty. This is what I found:

If you look at the face of the actuator you can see a groove cut into it at about the same height that the paper would hit it. 

I had a look at the paper that had jammed and could see marks on the edge at the position of the sensor. Next I manually feed paper into the sensor to see if it would catch on the groove. Yes it does.

It seems that paper hitting the actuator at the exact same spot 200 thousand odd times had worn a groove that was causing the jams. Strange that I had not seen this before. But I had never looked for this before either. I will now.

I sanded and polished the face of the actuator and ran some paper through the machine from tray 3 and could no longer get it to jam so I will definitely need to remember this.

Paper behind the trays

At least once per week we will get calls about a copier that has an error after a jam with a code C-0202, C-0204, C-0206 or C-0208. These codes will be displayed on a bright red screen that states that one of the paper trays can no longer be used. The message continues to ask if the user wishes to continue to press a "Continue" button on the screen then prompt the user to turn off then on the sub power switch which is on the control panel. If this is done as instructed the copier will work as normal except the affected paper tray will no longer be selectable. Usually the user will panic at seeing a scary red screen and call us or will fail to read the on screen instructions and turn the copier off and on at the main switch and will have the error again once the machine starts up.
The C-020x errors are common to all Konica Minolta Bizhub copiers and printers. The code refers to the paper tray lift motor malfunction and the last number refers to which particular tray is affected, 2 for tray 1, 4 for tray 2, 6 for tray 3 and 8 for tray 4. The error occurs when tray has been pushed into the machine and then engages the motor behind the tray that lifts the paper into the feed rollers above but the paper does not reach the upper limit sensor within a set period of time. If the machine tries to lift the paper in the tray but waits for a longer than reasonable time for either sensor that shows that the paper is at the correct height or the sensor that shows the tray is empty then the machine presumes something is wrong and stops.
While I have had a couple of lifting motor gearbox couplings fail in the last few years and once had an upper limit sensor fail these are fairly rare. Just about every time I see these errors it is because of a sheet of paper getting behind the tray and preventing the lift gearbox coupling with the lifting plate in the tray. The paper usually gets behind the tray if there is a miss-feed from the tray and the sheet ends up between the feed and separation rollers and the tray is then pulled out and the stuck sheet stays in the machine and falls behind the tray. When the tray is then pushed back in the sheet is pushed into the lift motor. To prevent this the on-screen instructions for clearing the jam and the instructions in the user manual both state that before pulling out the tray the lower right hand side door should be opened and any paper pulled out. But not many users read the instructions.
Removing paper from behind the tray is not as easy as it sounds even if know it is there. This is because of the group of switches behind each tray that detects the position of the guides in the tray to automatically detect the size of the loaded paper. To prevent accidental damage to these switches by people reaching into the machine the designers of the machines added brackets at the front to prevent the trays from being removed. The brackets are in different places on different models or even on different trays but are easy to spot if you know what you are looking for.
Once the paper is removed opening and closing the front door of the machine will clear the error code or if the tray has been locked out then switching the machine off and on at the main switch will allow the tray to be used again. After the tray can be used again the cause of the original jam should be investigated to prevent the chance of the same error happening again.
So the lesson is if you have a jam always check for paper in the right hand side of the machine before pulling the trays out.

Jamming at the horizontal transport unit exit

I am running up a new Bizhub C754e today with a FS-534 finisher and I am reminded of some problems with paper jams that I have had with this combination.
The first time we had trouble was with a customer who was an hour and a half drive away and was reporting "Jamming everywhere in the copier". Jamming everywhere usually means a jam in the finisher or towards the end of the paper path. Larger printers have multiple sheets of paper running through them at once to keep the time between prints as short as possible. A jam like this means that there is paper all through the machine when the jam occures and they all need to be removed before the machine will work again. This is described by normal people as jamming everywhere. In fact it is only jamming in the finisher.

I wasn't the first tech to have a look at the problem but the guy who was did a lot of testing but couldn't get it to jam. A couple of days later another call came in for the same problem so I went to have a look. All photocopiers keep a log of the latest jams including a code that describes where the jam occurred, the time, date and what paper was being used. When I looked at the log all I could see were document feeder jams. So I cleaned the ADF and replaced the feed rollers and then gave the machine a good test.

Since it was a decent drive to the office where the machine was located I really wanted to make sure that the problem was fixed but I had doubts. I was worried that we are missing something with jams not being logged so I turned on the option for the machine to display jam codes. Normally when there is a jam the machine will display a picture showing where paper needs to be removed from the machine but no information about what caused the jam. Now when there is a jam a code will be displayed on the screen. I asked the girl at reception if she could keep a manual log of any codes if the machine jams so we could have a better chance of fixing it.

Sure enough a couple of days later we got a call that the jamming had not stopped. I was surprised when I arrived that the receptionist had not only taken note of the lack of jam codes displayed but had used her phone to take pictures of the paper jammed in the machine before it was cleared. I was interested to see that not only wasn't the machine logging jam codes but won't display them either. The pictures though showed clearly that the front corner of the paper was catching at the finisher entrance. 

It didn't take too long after looking at the pictures that there was a groove cut into the plastic lower guide at the exit of the horizontal transport unit. 

The lower guide is removable (3 screws) and has a series of ridges that look like they are there to reduce the friction of the paper sliding over the plastic. However with the C754/FS-534 combo the edge of an A4 sheet lines up perfectly with the inside edge of the front most ridge. After a 200000 pages or so have gone through the paper actually cuts the plastic an causes a groove on the inside of this ridge. This causes the jamming.

To fix the problem we replaced this guide with a new one but that only fixed the problem for another 200000 pages and the jamming started again. So a final fix was to use a sharp knife to remove the bridge and then polish the plastic to smooth it out completely.

So the lesson here is to not always believe the logs.