A few weeks ago I went on a service call for a HP 4700 that had a blank control panel. Once I arrived onsite I observed that the machine was turning on and going through its normal start up procedure. However, the control panel, while lit, had nothing in the display. The three attention lights on the bottom of the control panel were also lit. After reseating the formatter, compact flash, and 256 MB memory DIMM nothing changed. I could not print to the machine but it did print the Engine Test Page.
In this particular case I ordered the Compact Flash and Memory DIMM and it happened to be the memory DIMM that resolved the issue. The best advice I can give if you run into this issue is to remove any accessories plugged into the machine, including EIO devices, memory, and compact flash. Insert each device one at a time and see if anything changes. Start with the Compact Flash, then memory, then EIO devices. I found that the memory and compact flash were relatively cheap so obviously the best place to start.
Note: On researching this problem I did find a few topics where the machine locked up after doing the memory count where the battery on the formatter had gone bad.
Service Manual Troubleshooting Tips
1. Reseat Formatter
2. Reseat Compact Flash
3. Reseat Memory DIMM or DIMM’s
4. Replace Compact Flashes and Firmware Card
5. Replace Memory DIMM
6. Replace Formatter
7. Check Flat Ribbon Cable Connector From DC Controller to Formatter
8. Check Formatter power connectors for LVPS
9. Check Control Panel display connectors to DC controller
10. Replace Control Panel display
Q7722-67951 256 MB Memory DIMM, 4700
Q7725-68003 Compact Flash, 4700
C7038-67018 Compact Flash, 4730
Q7495-69002 FORMATTER board, 4700 base model
Q7492-69003 FORMATTER board , 4700N/DN/DTN/PH+
RM1-1617 CONTROL PANEL,4005, 4700 – Control panel assembly
Kevin Gumpp is a certified printer technician and freelance writer for Market Point. If you have a question regarding this topic or have any other printer repair related questions or topics for which you would like more information, please send an email to email@example.com.