Have a x7400lx which is giving paper jam in DADF & U3-3511 or U3-3514 intermitently.

[x7400lx]

I have been trying to trace problem and have cleaned all sensors in feeding path and I also tested cable continuity from feed unit to PCB, but this only helped for a few single scans, I tried then 10 sheets and the feeding stopped at the 5th sheet and the error returned permanently . 

I also checked the daiagnotic service and paper size, paper detect and cover open switches all work but the rest give no results.

[Valsimot]

The ADF pickup and separator rollers are new and original?

[7400lx]

Hi, I am much obliged for your message. 

In the meantime, as I had tried to point out, the fault was definitely not feed mechanism related but electrical sensing. Hance, after I tested all relevant parts I ended up heating the PCB with a blower for a minute or so and the fault cleared permanently

Thanks all the same for your attention

Regards

Saviour Pace