C452 Dark Background Copy Problem & Solution

[srvctec]

Had a call several weeks ago for dark background on copies only, first thing in the morning only. They said it would only happen on the first 3 or so copies out in the morning, starting out very dark and fading very quickly on the next couple copies to being totally gone on the 4th copy. Customer said prints were fine but I had no way of knowing that for sure since how did they know someone didn't print to it and have the same issue. I basically went into this troubleshooting process with the mindset it was most likely doing it on prints as well.

I first re-secured all connections to the CCD (both ends of the cable), MFPB and PRCB, memory and NVRAM. They called back again in a couple days with same issue, so I swapped out the memory and discovered the K drum unit wasn't screwed in at all. They called back again with the same issue so I swapped out the MFPB with a known good one from our junkyard. I called them back the next day and the issue was still happening, still only on copies, they said. So, then I decided to take their word for it and instead of going further on the machine as a whole, focused only on copy related parts. I next replaced the exposure lamp, inverter board and scanner board and called them the next morning to find out that didn't fix the issue either.

I never could reproduce the issue while I was there until a few days ago, after replacing the exposure lamp, etc. I ran a copy and the issue occurred! Then I decided to run internal test prints to rule out the issue happening on prints and those came out perfect. Ran another copy and it still had the issue but had faded a lot since the first copy.

See the attached pdf files for how they looked.

The numbers on each file (#1, #2, #3, #4) are how they came out of the machine that morning and proves it was only on copies. The last things to replace in the entire copy only process were the CCD and cable. So, I replaced those and all is fine now. Good thing we had a good junk machine to take all this stuff off of so we didn't have to buy stuff!