The halogen fuser lamp in my HP 4M has apparently bit the
dust. (I'll know for sure tomorrow when I do a continuity check.)

It's a common problem with old printers.

They seem to go out around every 10 years. This is the second time it's
happened.

For 117VAC, you want an HP RH7-4046.

And an RH7-4048 for 240V.

I looked for replacements. Most companies won't reveal whether
they're selling real HP parts, or third-party units (of unknown quality).

There are some on eBay and others:
www.ebay.com/sch/i.html?_nkw=RH7-4046

The prices are all over the place. A genuine HP runs from $27 to over $60. I
found non-HP lamps for $4.50 -- but they want $10 for shipping.

You might also consider a fuser assembly swap. RG5-0879

Found several on eBay, from $25 to $40.

I wasn't aware of the brittleness of the plastic. I'll look closely.
Fortunately, I have the service manual, which makes things easier.

Fingerprints on a halogen lamp are a no-no. When I replaced my slide
projector's lamp, I cleaned it just to be safe.

hp laserjet 4 and 4plus how to rebuild and fix Fuser RG5-0879
http://www.youtube.com/watch?v=3GLlYoTDlkw
http://www.youtube.com/watch?v=pKdLjU_LAuQ

Looks mucho useful. Almost everything is on YouTube, isn't it?

I just told a friend to toss an HP LJ4 that he had in storage for many
years. Too slow and old. I would get a new printer, but we've been
through this before.

"Unfortunately", the 4- and 5-series LaserJets were made by Canon and are
classics. Yes, it's slow on graphics, but I don't use it heavily enough to
justify a new printer. Other than the toner cartridge and fuser lamp, it will
probably outlive me. What would I buy of the same quality?