HP 71B Diagnostic ROM

[Dave Frederickson]

I have a theory. First, here's my 1BBBB from '84. Notice the brightly colored key legends and the three screws visible on the back side. This is typical of the early models with 1BBBB ROM versions and the metal back. Date code 2422A.



Next is a 2CDCC with a plastic back. Notice the lighter colored key legends and the absence of the screws in the back. Also, there are two new screws in the battery compartment, located near the "golden zebra" connector. See the FRAM71 doc for a picture of the board-to-board connector. Date Code 2902A





Finally, here is the 71B in question. Date code 2707A.


I don't see how an old front and a new back, or vise versa, could be possible since the connector is physically different. The old version has a fragile flex cable and the newer version a zebra connector. The interior shows no signs of refurbishment, unlike my 2422A which I had to send in for repair. HP left a little note stuck to the top of the HP-IL compartment.
I suggest that when the CPU/Display board was being assembled that 1BBBB ROMs were used, perhaps because HP's disposition of old version ROMs was to use until depleted.

My explanation for Joe's Frankencalc is that at one time it had a lobotomy. Someone repaired the calculator by replacing all the ROMs. Joe, does your 71 have bright or light colored key legends?

Dave