MP 201 misting

[ABS tect]

I find that these 161,171,201's tend to get pretty dirty on the inside from toner. Is this always the PCU's fault? whether it is just at the end of its life or the developer is going bad? Or could the toner hopper also be to blame?

[sandmanmac]

I find that these 161,171,201's tend to get pretty dirty on the inside from toner. Is this always the PCU's fault? whether it is just at the end of its life or the developer is going bad? Or could the toner hopper also be to blame?

It's always the toner hopper unless the PCU is WAY past PM.
Replace it.
Same with the 2027/3350/51/52, etc. series