Hit it! If you find the spot that makes it work, mark it with an X.
I don't recall having a blank screen unless it was related to an open
interlock while fixing a paper jam or changing the toner. You might try
opening all the doors, making sure the toner, duplexer and all the green
levers are in the right position, and closing the doors securely. If this
doesn't fix it, you probably need an HP service person.
Do you know the machine's IP address? If so, you may be able to access
its web page using a web browser. For a URL use the IP address, as http://192.168.11.5, using the correct IP of course. See if there is an
error condition listed there.
If the printer has AppleTalk turned on, you may be able to access the
printer using the HP LaserJet Utility on a Macintosh computer. I doubt it
would give as much information as the web page, but it would let you know
the printer was alive.
If all else fails, you might do a reset. You do that by holding down the
Pause/Resume button while turning the power on. This is a last-resort
option since it resets everything to factory defaults and probably won't
fix the problem.
First thing to check is whether the engine test works.
1. The engine test button is located on the right hand side of the printer,
just below and to the rear of the control panel. You should see a small hole.
Use a non metallic object like a tooth pick and push the button that is behind
the hole. You should get a print with either a series of lines or a black page
(can't remember which is the correct one for this printer).
If it does not print a page, remove the formatter and try again. If it works
this time it is a formatter problem or reseating the formatter has corrected a
poor connection, so if it prints you should re-install the formatter and verify
that the problem is still there before you look for a replacement formatter.
2. If the engine test works with the formatter installed (1. above) then there
are several possibilities.
Remove the formatter, if the panel lights up the formatter is bad.
Check that all connections inside the printer are good and remove and replace
If not fixed the likely causes are...
Control panel cable (unlikely, never seen one fail).
If you have another 4200 available or can borrow one, you could swap parts one
at a time.
3. If there is no test print at all then then the likely cause is the DC
Controller or power supply.
Sorry if this is a bit cryptic.
Let us know how you get on, if you would like the service manual I can e-mail
it to you but I will wait until you report back since it is a BIG file.