I have owned a 7900 since 9/7/2011 and I am adding this post because it may help other Epson owners. My machine did not work right from the first day I owned the machine. It took four service calls and now the printer functions like it should. The problems I was experiencing was complete nozzle check patterns missing on the PK,MK/LLK nozzle pair(if the printer sat unused longer than 2 or 3 days), ink starvation or nozzle drop outs if I printed one or two 30 x 20 prints, and the printer would take multiple cleaning cycles to clean clogged nozzles. I let the Decision One do all the repairs but I wanted to figure out was going on, so I acquired the Epson Stylus Pro 7900/9900 Service Manual and the Pro 7900 and 9900 Field Repair Guide.
The first Service call the wiper was cleaned and I was told the clogging issues was due to "morning sickness" (nothing wrong with the printer). The wiper is a small piece of rubber that is used to clean the print head.
The Second Service call the capping station and the wiper was replaced. This fixed the PK,MK/LLK nozzle pattern missing problem.
The third service call the ink selector was replaced. The ink selector does the PK,MK switch but also contains all the dampers for the 7900. This part solved the ink starvation, drop out problem.
The fourth service call the Print Head was replaced. Right before I placed this service call I had a small clog on the LLK nozzle. I attempted to do a CL1 and CL2 pair clean in service mode. The clog would not go away. I let the printer sit for an hour and did another CL2 pair clean and a normal clean. The clog finally cleared and moved to a new location on the LLK nozzle. I turned off the machine and called Epson Support. After the print head was replaced all cleanings are resolved on the first cleaning attempt (either pair or normal clean).
For people who want to service the machine on the own, it is possible if you are mechanically inclined. I do not believe that the print head can be replaced by most people. This is because once the print head is replaced, the following three things must be done. The NVRAM (non volatile ram) must be updated before the print head will even be recognized by the printer. Then the Horizontal and Vertical adjustment must be adjusted for the print head. This is done by running two separate routines in service mode and adjusting the adjustment screws on the print head.
For people who want to service their own printer you need the following four items.
Epson Stylus Pro 7900/9900 Service Manual
Pro 7900 and 9900 Field Repair Guide
Parts Manual Epson Stylus Pro 7900/9900 (this is just the mechanical drawings)
servprog.exe for epson 7900. This program will write and read information from the nvram in the 7900. required for replacing some parts.
Parts can be bought from:http://www.epson.com/cgi-bin/Store/AboutEpsonConnection.jsp#section5
or google "Epson parts distributor"
When ordering parts you need to supply the product name Epson Sylus pro 7900, and the mechanical part number. You need to tell the distributer the number came from the mechanical drawing and they will cross reference this number to the real part number.
Part numbers for Epson 7900 for the following parts:
Part Name Desciprtion Mech # Epson part #
PUMP,CAP,ASSY,B,ESL,ASP capping station 567 1523796
WIPER,ASSY,ASP wiper 568 1504179
SELECTOR,UNIT,ESL,ASP ink selector/damper 526 1504216
PrintHead Printhead 523 F191010
The labor rate for Decision one in my area was $100 to show up and $175 a hour. They took about 4 hours for each service call.
I was told by Decision one that the Printhead could not be purchased from parts suppliers and could only be obtained from them. They said the cost of the print head was $1800.
If replacing the Dampers or the Printhead you need to take into account the amount of ink that must be purged through the lines when these parts are replaced. It takes several power cleans. When the dampers were replaced 45 % of the Maintenance Tank was used and the Print Head used 40 % of the Maintenance Tank.
The Service Man warned about the edge connectors that Epson uses on their ribbon cables. If these cables are not plugged back in correctly, it is possible to short power and ground which will fry the circuit boards in the machine.