MX-M450N - C1-00

**oeshuron** · 07-12-2018

I know it's old but we have an MX-M450N with C1-00. Can't get anything out of it. Tried different DV unit, drum, main charge, door (with hv resist pwb), pcu pwb and still throwing c1-00. Also replaced High Voltage PWB.

**mansart** · 07-13-2018

Put a meter between frame ground and where the contact where the charge corona plugs into rear frame (not the grid but charge). If you have continuity....check harness for a pinched wire.

Having replaced all that you have my gut feeling is you have a dead short to frame

**oeshuron** · 07-13-2018

Originally Posted by mansart

Put a meter between frame ground and where the contact where the charge corona plugs into rear frame (not the grid but charge). If you have continuity....check harness for a pinched wire.

Having replaced all that you have my gut feeling is you have a dead short to frame

This was my thinking as well. Just a matter of trying to find it.

**oeshuron** · 07-13-2018

The machine has the following different items on it currently:

HV PWB, Main Drive Unit, Drum Unit w/new MC, Side Door, and PCU PWB. Still throwing C1-00. Checked continuity between ground and charge contact springs and there was none. There are different wires from different main drive unit going to different hv pwb. Drum ground to frame does have continuity.

**oeshuron** · 07-17-2018

Checking PCU CN15 what does anyone get for continuity reading from MHV-T (Pin 13 IIRC) to ground?

**niceville318** · 07-17-2018

These models have that Mother PWB that's buried within the machine. Although it looks like a pass-through pwb I've seen them fail and cause problems that had me chasing my tail. Based on the items you already replaced I would take a second look at that one. Sorry can't be more specific on what to look for but that pwb was usually a last resort and fixed the problem a couple of times. Just be prepared to practically dismantle the engine.

**oeshuron** · 07-17-2018

Well it's working. The MHV-T pin in CN15 of PCU PWB showed some continuity to ground in the original PCU. I was wrong that the replacement PCU was installed in the machine when it was brought in here. Tech said he had it switched out at one point onsite and still got C1-00 so not sure if it was a combination of two different things or not however the replacement PCU read open on the the MHV-T pin. We are not switching parts back to find out though. It's just going back at this point.