AF-1060 & 1075

[tcs04]

I agree (Kopykat / Breaker)

Any of the above could be the cause.

[imthinman]

Check the hopper

Separate the upper half of the dev unit( the hopper) put down an 11x17 and turn the toner drive while watching the tiny toner exit holes you probably have some stopped up and is not adding sufficient toner for the toner on time. Especially if using generic toner.
Imthinman

[tecnoacre]

See also Development power pack is not got any dirt toner, I had a problem and clear copies of the plate with a crust of this toner

[Shadow1]

But MP4500's (??) don't have a hopper with a toner end sensor.

On this machine the machine should display "add toner" long before the dev unit runs out of toner due to the front end of the hopper being empty.

Should, but some of them don't, and I have not been able to see any pattern to it. Sometimes the hopper fails, the copies get light, and I get called for an SC390. There is usually toner left in the bottle, so I suspect the customers open the cover a few times trying to reset it, but... anyway has nothing to do with this problem.
If you can force add toner and it makes better copies then the toner feed is working, and there is at least some toner in the hopper. If the machine is not saying Add Toner the hopper sensor is not the problem - this is of course after it has time to rotate the bottle 10 times if the sensor is bad and the machine thinks it's empty (this would also add toner and possibly cause the machine to overtone because the hopper agitator and toner feed are on the same clutch on this model)

That leaves one of the process sensors: ID, TD, or Drum Potential. Of course a shoddy PM or bad drum could fool these sensors...