The HP DesignJets 430 and 450C are physically the same. The numbers on the plastic molding are different, and a few configuration bits in some EEPROM are different, but that's it. The 430, a black-and-white printer, comes with a 4-cartridge carriage, the color portion of which is filled by a spacer. The standard way to upgrade from this configuration to the color 450C is to use HP part number C4718A, a $400 upgrade that includes a ROM SIMM which overrides the printer's firmware. You can occasionally find instructions on how to do the color upgrade without extra hardware for $20ish on eBay. Initially I was skeptical, particularly since some quick Googling failed to turn up the same information for free.
As it happens, you really can do the upgrade without added hardware. You just need about an hour and a willingness to do some scary things to your printer after disassembling it.
You'll need a few thing before you start:
- The HP DesignJet 430 Service Manual (3.4MB) (local mirror), particularly pages 130-133 and 61-62 (print these out).
- A standard (flat-head) screwdriver. Longer is better.
- A torx T20 screwdriver if you have the rollfeed assembly.
- A good space to work, with electricity available, preferably off the floor.
These instructions are not a replacement for the instructions in the service manual. They are my comments on those instructions, intended to make the procedure easier for first-timers. So take a deep breath, grab your manual print-outs, and dive in:
- Remove the top cover (Page 8-8, or 130 in the Service Manual). "Slide the cover to the left" means bang on it a bit so it comes apart. The whole thing flexes alarmingly.
- Remove the rollfeed assembly, if you have one (Page 8-9, or 131). You really only need to unscrew the parts a bit so there's room to get your hands on the right end-cover. I found it useful to leave the printer partially on the rollfeeder to keep it a few inches off the table.
- Remove the right end-cover (Page 8-11, or 133). HP's warning about the retention clips that "these may be stiff" is an understatement. Sliding the printer slightly off the table so you can look at the bottom will be helpful here. Jabbing at the plastic tabs with your flat-head screwdriver might help too. Gently lift off the end-cover and unclip the display assembly. Lay it aside.
- Reconfigure the EEROM (Page 4-27, or 61) as a 450C.
- The main PCA is the circuit board you can see if you look in the right end of the printer. Push the flat ribbon cable out of the way to see in. Connector ENC X that you're looking for is the connector nearest the back of the printer, the one with 5 (I think) pins. That's on your right as you look in the right end. Reach in with a screwdriver and pry it up a bit, then completely off. It may be helpful to stick some fingers in through the small access hole in the back of the chassis. The hardest part of the procedure is reaching in and unplugging and then re-plugging this connector.
- After step 10, when you reconnect the media encoder cable, leave the printer disassembled. Put the power button in and turn the printer back on, or use your screwdriver. Print the Demo Plot to be sure you did everything right. I had to unplug/short/button-press/re-plug twice to get it right. There's a plastic lever on the right side of the display panel assembly that checks to be sure the lid is closed. Hold that lever down if the printer complains that the lid is open, and won't print. Keep your hands away from the carriage...
- The demo plot prints bottom-to-top. You'll know if you did things properly if the text at the bottom mentions 300 x 300 dpi color. If it starts printing the demo architectural drawing and you don't see anything about color, you'll want to cancel the plot and reconfigure the EEROM again. There's no point waiting for the demo to finish.
- That's it! Power off, clip the display back into the right end-cover, put the end-cover back on (line it up carefully and bang on the top a bit to get it to click back into place), put the top cover back on (banging is required here too), and install the three color ink cartridges. You should probably run the accuracy calibration, black cartridge alignment and/or color cartridge test sheet at this point to make sure you didn't bump anything and the new cartridges are happy and lined up properly.