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HP Forum Archive 18

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My brand new HP35 (odd problems)
Message #1 Posted by Steve (Australia) on 29 Jan 2008, 4:40 a.m.

OK, so it was brand new 34 years ago...

I know this isn't exciting to lots of people here, but I got one of these in the grey hard case that is in very clean condition.

Naturally the battery pack was dead, so I carefully split it open and replaced the cells (temporarily) with 3 NiMH cells. I put a small piece of foam rubber at the end of the pack to hold the batteries tightly against the connections and the links (made from aluminium foil).

It now works fine except for a minor issue or two. I'm wondering if anyone can shed any light on them.

The first thing is that the calculator doesn't turn on every time. A light press near the power switch generally fixes that. Could it be the switch is dirty? Wobbling the power switch lightly sometimes makes all the decimal points seem to light up. Is that the low battery warning?

The second thing is that I see a brief of numbers across the display when it turns on. Is this normal? In fact once it turned on with a display something like 000- 010.

The third thing (and I guess this is the big one) is that the last digit on the display has a few segments that light up dimly, but get brighter as the display contains more and more digits. If I enter 8.888888888888 the top three segments of the last digit are about half as bright as the rest of the numbers, and another segment (which isn't either the decimal point or any regular other segment) is lit at full brightness.

The last one is strange as I assumed the displays would be normal 7 segment displays. (It could also be my eyes).

The exponent end of the display is at the same end as some discolouration of the red sticker over the battery pack. Is it possible I could have an issue with corrosion in there? Can these calculators be opened without introducing cosmetic flaws? It really is in nice condition otherwise.

      
Silly me -- that's the decimal point
Message #2 Posted by Steve (Australia) on 29 Jan 2008, 4:48 a.m.,
in response to message #1 by Steve (Australia)

When I was looking at the display I was expecting the decimal point to be where it is in all modern 7 seg displays.

The segment that lights up fully is the decimal point.

      
Re: My brand new HP35 (odd problems)
Message #3 Posted by Jeff O. on 29 Jan 2008, 1:21 p.m.,
in response to message #1 by Steve (Australia)

Quote:
The first thing is that the calculator doesn't turn on every time. A light press near the power switch generally fixes that. Could it be the switch is dirty?

Yes.

Quote:
Wobbling the power switch lightly sometimes makes all the decimal points seem to light up. Is that the low battery warning?

Yes.

Quote:
The second thing is that I see a brief of numbers across the display when it turns on. Is this normal?

It is common behavior - if you have a dirty power switch.

Quote:
The third thing (and I guess this is the big one) is that the last digit on the display has a few segments that light up dimly, but get brighter....

Display problems are fairly common in these units. A similar problem was discussed in this thread.

Quote:
Can these calculators be opened without introducing cosmetic flaws? It really is in nice condition otherwise.

Sure. This message provides some basic information, ask if you need more. The biggest issue with disassembly is accessing the screws under the label peeling the label back vs. poking holes.


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