c550 grainy copies

[acsolutions]

hello,
I have a c550 all images washed out (black and color)! checked image on belt during coping, image hass good fill on belt. checked voltage on transfer roller there is less than a volt when turned on! could this be the hvt? what turns on the hvt? when the paper pass over the roller there is a voltage fluctuation .5 volts..

Thanks

[Stirton.M]

HV2 controls the voltages applied to the second transfer roller. This is regulated by the PRCB. Problems related to this may generate a P27 code, though not necessarily.

300 V to 5000 V (ATVC-2nd) is the range for that section. It can be viewed in State Confirmation, level history 2.

From there, what are the values for all as seen on that screen?

[acsolutions]

checked value

ATVC 2nd value is "0"!! I had mentioned earlier that I had my meter on the transfer roller and when the paper passed the roller there was a voltage fluctuation between 0 and .5 volts AC. I imagine that im getting the signal from the prcb to turn on the HVT2, is this correct?

[ebm]

ATVC 2nd value is "0"!! I had mentioned earlier that I had my meter on the transfer roller and when the paper passed the roller there was a voltage fluctuation between 0 and .5 volts AC. I imagine that im getting the signal from the prcb to turn on the HVT2, is this correct?

i am interested to know how you read voltage from the transfer roller while the machine is making a copy. This may come in handy in the future. Thanks.

Also, have you checked into the 2nd transfer roller pressure mechanism. This would be an easier problem to fix than the high voltage. Good luck.

[acsolutions]

I made up two small gauge wires with alligator clips on both ends. I connect one end to the electrode on the transfer roller assembly and the other to ground with my meter in between. I ran this same test on another machine and got the voltage I was looking for! I didn't know I could for voltage presents in the service mode!

[Stirton.M]

You should be able to view the value directly when you are looking at that one tech screen and press the print button to see the levels on the fly.

But in this case, it is safe to say HV2 has failed somehow and should be inspected/replaced. Be careful, it may not be the board itself. A poor connection, or a failure somewhere else that controls that board.

[acsolutions]

today was another day of diagnosising this problem!

checked voltage at hvt showed 139vdc and read the voltage at the connector it was also 139vdc checked continuity between the connector incoming wire and the metal tab that is at the transfer roller guide with the door closed was ok also checked voltage in this area it was 139vdc. State Confirmation, level history 2 in service mode is ATVC-2nd is 300

I am not sure what the hvt voltage should be, should the voltage change when I make transfer roller adjustments in the service mode? I disconnected the transfer voltage wire to the roller and the copies did not change! I also disconnected the the seperation hvt wire and the copies were much lighter. made transfer roller output fine adjustments going in + and - direction without any change in copy quality. noticed running two sided copies the second side was much lighter than the first.