HP-34C, spice calc's, what about "2 disease"


Haven't posted here in awhile. For those who don't know, I am the #1 proponent of 34C and its cousins ... when working properly I think the 34C in particular is superb, both cosmetically and operationally.

Was just noting, with another 34C owner, a unit that has contracted "2 disease". This is a condition that still allows the unit to function, but the display does not blank properly, causing annoyance by flashing more than necessary.

A unit with full "2 disease" will show flashing while it computes sin(x) for example. And it blinks with each press of "2" (i.e. enter 2.2222222).

What are we gonna do about this? I remain convinced that it is an irreversible damage to the silicon chips (probably ESD or overvoltage) and is triggered either by servicing the units (like servicing without fullest ESD precautions) or it is caused by running the units when they have intermittent internal connections.

The problem is, with solderless circuit boards, the unit gets an intermittent, then the user runs it anyway, then it gets "2 disease" ??

What are we gonna do about this ?


I cleaned the contacts of my HP-32E (not soldered also) with pencil eraser (soft white rubber) until the entire board gets a bright and clean aspect (not too much, and not much harder to not damage it).
Mine was missing digits and segments of the display, now is good as new.




Be careful with both eraser debris and with static caused by friction between the eraser and the board (just in case there are electronic components still connected to the board, apart from the solderless chips)


At least in the case of the HP-32E, you can disassemble it entirely, leaving only the flex board and the metal/foam base (no electronic components at all).
Yes, you must clean all the debris with a brush or anything like that.
You must take care to not touch the IC's pins, they are ESD sensible.

As I said, mine is now fully functional.




I think nothing can be done. Just take care when repairing these units. I also recomend charging the cells outside with a battery pack charger (just in case).


Has anyone compared the "bus behaviors" of two units side-by-side -- one with the "2 disease", one without? Has it been decided what electrical characteristic results in the flickering? (E.g., are common cathodes or anodes not held low or high during use of other shared lines for internal ROM accesses, etc.?)

If the actual breakdown could be elicited, I wonder whether then it might be possible to beef up a pin or two through the use of an external resistor or something like that?

One has to wonder whether anything can be done . . .

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