Bizhub 420 paper size????

[krazeekidz3]

I have a BH 420 that I have now brought back to the shop. It keeps showing question marks where the paper size should be displayed. If you select that tray, the message says replenish the paper. The paper IS being lifted. This is happening intermittantly on both trays.
First, I blew out the sensors. Seemed fine for a day or two. Then it began happening again. Replaced the sensors.(PS5, PS6, PS10, PS11 only on tray 1, to start) It was fine for a day or two. Guess what! Same thing. I saw on the KMBS website to change the marketing area to Europe then change it back to US. Did that. Again, it was fine for a day or two! I then swapped out the PRCB board and that didn't change anything.
I'm thinking that I may swap out the size detect boards next, but isn't it odd for BOTH boards to go out at the same time?
Or maybe a short in one of the wires in the harness?
Any suggestions would be greatly appreciated!!!
Thanks!!

[ebm]

Konica came out with a new style holder to hold the paper trays in. The new holders are black and you have to order a wire stopper ring with it. I use tie-wraps around the original white holders to "squeeze" them together for a tighter fit. Just a suggestion.

[fixthecopier]

What ebm is saying may be the problem. I know that on the 250/350 machines there is a problem with the drawers not staying shut all the way. Can cause it to not be making contact with sensors.

[mo0651]

i've had a couple of these where the size sensors, behind the trays, the whole assembly was bent. I think it took a hit in production. Take both trays out. and take a good look at the sensor rack. they will shift a little when you loosen the screws. Something else to look at.

[BlueBlazer]

I can confirm the same problem on our shops BH 420, Tray 2 has been intermittently going out, you have to hold it in place for a few seconds before paper is detected. Recently our LCT Tray 3 has been showing the same problem as described by krazeekidz3; not detecting paper even though paper is being lifted.

I don't possess a 420 FS manual, but would someone provide a hint where I could find this sensor?

[tech51]

Also the rear paper guide plate in the tray can bend slightly backwards causing the channel with the cutouts for the size detectors to sit low and miss the sensors when the tray is inserted. The cure is to gently bend the rear paper guide back to the vertical.

[mabawser]

Had the same fault as tech51, takes a couple of seconds so would be easiest to rule out 1st. had it loads of times although mainly on 250/350 machine

[mascan42]

Also the rear paper guide plate in the tray can bend slightly backwards causing the channel with the cutouts for the size detectors to sit low and miss the sensors when the tray is inserted. The cure is to gently bend the rear paper guide back to the vertical.

The older machines don't have the lifting stay bracket at the rear frame of the drawer. Adding it will fix this problem as well.

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