1st Gen HP-35


Can anyone enlighten me on the following?

I just picked up a S/N 1143 calculator. Thought it might have "the bug", but it doesn't. I have a S/N 1249 calculator with the bug.

Both have raised dot on the 5.

The back label on the earlier calculator matches one I have starting at 1302. These labels state on the top HEWLETT-PACKARD HP-35 INSTRUCTIONS whereas the '72 unit only has HP-35 INSTRUCTIONS. Does this indicate the unit was sent back for repairs and the different label was applied?

I do notice the battery compartment is two piece and can see the board through the slight crack.


Hard to say. I have a s/n 1249 version 2 with the bug and the label has HEWLETT-PACKARD.... on the top. So, I'm not sure if a s/n 1143 version 2 should not have this version of the label as well. I've also seen labels w/o the Hewlett-Packard name on other HP models of various vintages, so it is inconclusive. Maybe it was returned to HP for repair or maybe someone mixed parts. It's also possible that it never had the bug in the first place. As to the battery compartment; I believe thay are all two piece, but some have a noticeable gap, whereas others are flush so you can hardly see it.


Very likely (like in close to 100%) this one has been sent to HP to replace the bugged ROMs - the "old" backlabels probably were no longer in stock, so they just stickerd current ones onto the calculator.


See this current TAS auction and look at the photos. This is a s/n 1143 HP-35 version 2 calc with the bug and a rear label with "HEWLETT-PACKARD MODEL 35 INSTRUCTIONS" on it. Notice that the serial number is inside the battery compartment and not outside as on some earlier production. So, like I said, the type of label is inconsequential. Yes, the calc was probably sent to HP for replacement of the ROM, but the label is not the determining indicator of this. The only way to know for sure is to open the calc and look for stickers on the pcb and ROM numbers.

Edited: 17 Feb 2011, 11:09 p.m.

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