HP35 with "The Bug" - latest s/n and version?



#5

Anyone know the latest known serial numbers of HP-35's with "the Bug"? Also were buggy HP-35's seen in the 3rd version (with the 35 on the HP logo plate)?

TIA

-- Dan


#6

I have never see a version 3 HP-35 with the ln bug. The latest version 2 that I have is 1143A58xxx, and it has the bug. While I don’t know for sure, I believe that the next batch of version 2 HP-35’s started with 1230A, indicating that production of this batch began around the last week of July1972. I have a photo of the letter that HP sent out to owners describing the bug and offering to repair their calculators. Unfortunately, the letter does not seem to have a date on it. It does state "We have taken immediate steps to correct the problem, and will have replacement read-only-memories available sometime after the first of the year." Presumably, that was after January 1, 1973. Dave’s list of serial numbers indicates the earliest version 3 started with 1302A. This is consistent with the above letter and the conclusion that they corrected the roms and started producing the version 3 bug-less models in early 1973. My version 3 unit is S/N 1302A98xxx, no bugs in sight.


#7

Thanks. that's helpful and interesting. I found an HP35 with the bug at a garage sale, date code 1230A But it had been opened, so one never knows what may have been swapped in or out.

I opened it up and found a datecode on the mainboard: 1218.

I've noticed that some datecodes show up a lot, like 1230, 1302, 1143. It seems to me the datecodes changed more with some revision than with the dates.

Also some early HP35's have a 2 piece center plate with 10 screws and later ones have a 1 piece with 8 screws. Anyone know when this change took place?

-- Dan


#8

Quote:
I've noticed that some datecodes show up a lot, like 1230, 1302, 1143. It seems to me the datecodes changed more with some revision than with the dates.



The common serial number explanation is that the first two digits are the year of manufacture (minus 1960), the second two are the week number within that year, the letter indicates country, then the last five digits are the individual sequence numbers. So, the first four can be called the date code, and as you say, some date codes show up a lot. I have no direct evidence, but I do not believe that hp changed the date code at the beginning of each new week. I think it was changed only when certain events occurred, such as:

1. they produced 99,999 copies with a particular date code (assuming they would not produce a unit with a sequence number of "00000".)

2. a fairly major design change was implemented, such as the updated roms between versions 2 and 3, or the keyboard design change between versions 3 and 4.

Quote:
Also some early HP35's have a 2 piece center plate with 10 screws and later ones have a 1 piece with 8 screws. Anyone know when this change took place?



My version 2 units are all 1143A and all have the 2-piece center plate with 10 screws. My 1302A version 3 has a single piece center plate, and presumably only 8 screws, although I have not disassembled it. Does your 1230A unit have a 1-piece or 2-piece center plate? If it is 2-piece and if I had to conjecture, I would say that the 2-piece to 1-piece center plate change coincided with the version 2 to version 3 change.

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