HP-32E missing digit



#13

Hello all. I just got a HP-32E and it turns out that all but the last digit/diode light up. I heard that there's a burnt diode issue with the Spice/Series calcs. True?

If my value on display is the full 10 digits, I need to subtract the integer to get the full decimal value so I can catch the missing digit. Or, if I've got a number in scientific notation, I need to take the logarithm of it to find out the two digit exponent. This kind of thing can be very cumbersome just because I've got a blown diode.

Has anyone seen this before?Any thoughts?

Edited: 19 Mar 2012, 10:33 p.m.


#14

HI.

The Spices have two different assemblies: one with all major components soldered in a rigid mainboard (lighter units) and another one, the 'solderless' units, where all major components are simply kept together by a rigid-plastic chassis (provides alignment) with their terminals pressed against a flex-circuit. The LED display itself is also kept pressed against the flex circuit through its terminals. Since the LED display is multiplexed, chances are that your unit is of the solderless type. In this case, considering you may have a bad contact, a gentle, slight case twist may cause the missing digit to work again. Don't force it at all, just a slight twist while the calculator is ON. If the missing digit is not back, you can disassemble it and check if it is one of the solderless units and try sliding the LED module back and forward. If it is soldered in place, a last minute guess would be touching the solder points with a low-power soldering iron tip and heating the solder points, and if any of them is cracked (or a cold solder), it will probably bring it back.

There are some references (with pictures) on how to disassemble and reassemble these beasts, just check in this forum.

Success!

Luiz (Brazil)

Edited: 20 Mar 2012, 12:32 a.m.


#15

Hi there. Why couldn't it be that the single diode itself is burnt out? Or is it like Christmas lights that if one bulb is out, the whole string is out? Not certain what you mean by twist. The thing is solid. How can I twist it? It's not like I'm wringing a towel is it? Just exactly how (and please be very specific) am I supposed to twist this solid calc?

Edited: 20 Mar 2012, 12:29 p.m.


#16

Hi.

I actually do not know what diode is the one you mention because in all SPICES, the whole LED assembly and the keyboard are directly connected to one main IC, the big one. In the HP32E there are two other IC's, a ROM and a RAM.

The LED module has only the LED's array to be scanned by multiplexing circuits in order to 'light them up', one digit at a time (very fast, human eyes cannot 'see' them blinking). If the common terminal of one digit (not sure if they are common cathode or common anode) fails, the whole digit does not lit.

The twisting maneuver is something that I apply to my calculators. I take it with both hands, bottom an top (closer to the LED display), and gently twist it along its axis. My spices are not that solid, they all allow a little twist, which is enough to maintain contact in the solderless units. As I mentioned before, if twisting is not an option, opening the unit is somehow better.

Succes!

Luiz (Brazil)


#17

Quote:
I actually do not know what diode is the one you mention because in all SPICES, the whole LED assembly and the keyboard are directly connected to one main IC, the big one. In the HP32E there are two other IC's, a ROM and a RAM.

He is probably talking about a (Light Emitting) Diode.
I have had problems with a display where a leaky battery caused corrosion within the LED array and some segments failed. It also could be a bond wire that has come loose.
But contact problems as you described are also very likely.


#18

Quote:
...I have had problems with a display where a leaky battery caused corrosion within the LED array and some segments failed...
+1. The most common (non-repairable) display failures in spices is the loss of the right most digit - due to corrosion from the battery tab area leaking into the display and either lifting the die off the board or opening wire bonds.


Edited: 20 Mar 2012, 8:40 p.m.


#19

My 32E shows the missing digit problem, it affects randomly more than one digit. Also, digits can show incomplete. But if I press slightly the battery door then the problem disappear and all the digits show nicely. Could it be a contact problem as mentioned earlier? Is it repairable?


#20

I wonder if the folks at FixThatCalc.com could take care of that.


#21

I have firsthand knowledge that FixThatCalc has no parts for Spices ;-)


#22

PS Matt, in case you haven't figured it out: Randy = FixThatCalc !!!


#23

Surely: Randy >= FixThatCalc!! :-)

#24

HI.

This is the very symptom of a bad contact commonly manifested in solderless units (not a definitive, 100% proof of it, though). I'll try to find pictures showing the differences and post them here.

Cheers.

Luiz (Brazil)


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