HP 48gx construction quality question

[Joe Edwards]

Folks,
Last question for the night. How's everyones' knowledge regarding the construction qualitiy of the various HP 48gx models? I have a model made in Singapore and also a model made in Indonesia, with the black LCD. Should I expect any difference in the two calcs' construction...long term wise? Thanks

Joe

[Randy]

The major difference is a Singapore has double shot molded keys, the Indonesian, printed keys.

IMO keyboard tactile feel in the Singapores is better as well. The same applies to Pioneers since they were manufactured in the same facility. A Singapore 32Sii is head and shoulders above a Indonesian 32Sii for keyboard feel. Indonesian Pioneer keyboards have a nasty habit of making snapping and popping noises when the keys are pressed or released, for some reason the 48's don't have this trait.

We beat this topic to death a couple of years ago when the 32Sii was discontinued, there's thread after thread in the archives.

[Thomas Radtke]

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Indonesian Pioneer keyboards have a nasty habit of making snapping and popping noises when the keys are pressed or released, for some reason the 48's don't have this trait.

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You haven't heard my Indonesian 48G yet. Impossible to pass the library security with this calc;). The fact the the housing is half empty amplifies the pop and click noise a lot, I believe.

Thomas

[Han]

Hi Joe,

There are structural differences, in my opinion. Having taken apart a few, I can say that the rivets in the older models are much better heat-fused to the contact points. In the newer models, the rivets can easily be pried from their contact point with the upper half of the calculator (i.e. the keyboard and LCD section).

As others have already pointed out, the keyboards are also much nicer in the older models.

As for the internals, the older models have a zener diode that helps prevent electrostatic discharges. This component was later removed from the newer models. My guess is that it they did this to prevent the diode from becoming a battery drain. Some owners have reversed the polarity of the batteries as a way of "resetting" their HP48s. Of course, in the older models, the zener diode would prevent this. Unfortunately the diode often becomes resistive, so that when batteries are installed correctly later on, they get drained by the diode.

And lastly, the LCD in the older models had a protective piece of plastic that protected the backside of the LCD. I think this helped prevent the LCD from being bent even slightly.

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Folks,
Last question for the night. How's everyones' knowledge regarding the construction qualitiy of the various HP 48gx models? I have a model made in Singapore and also a model made in Indonesia, with the black LCD. Should I expect any difference in the two calcs' construction...long term wise? Thanks

Joe

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[Randy]

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And lastly, the LCD in the older models had a protective piece of plastic that protected the backside of the LCD. I think this helped prevent the LCD from being bent even slightly.

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The early 48's (both G and S models) up to mid 1994 did not have the reinforced LCD. HP had too many warranty claims on broken screens so they added that piece of black plastic stuck to the backside of the LCD to help decrease the breakage rate. Those S and very early G non-reinforced LCD models also tended to be the lower contrast blue which was updated to a darker blue about the same time as the LCD plate was added.

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As for the internals, the older models have a zener diode that helps prevent electrostatic discharges

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It wasn't there for electrostatic discharge... it was there in case you installed your batteries backwards, in which case the diode was forward biased and clamped the reverse voltage. Only problem was it was too small to handle the current and usually shorted. Since "installing the batteries backwards" trick was one of those urban ledgends that spread like all things bad, it was easier to eliminate the diode. HP did test and found reversed voltage wasn't much of a hazard as originally evisioned and was a better risk than battery eating, shorted zeners. So it was bye-bye zener. They dropped out by early 1996.

[Han]

Randy,

Thanks for clearing those two bits up. I do have one related question:

How often is it that when an HP48G no longer powers up, the cause is black electrolytic capacitor (next to the ROM chip) being defunct?

I have an older HP48G that no longer powers up, and cannot seem to diagnose the cause of the problem. Do you have any tips on diagnosing the cause of a working calculator simply going kaput?

[Randy]

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How often is it that when an HP48G no longer powers up, the cause is black electrolytic capacitor (next to the ROM chip) being defunct?

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<1%

Have you tested the logic board on a known good keyboard? On older used units it's most likely not the logic board but a shorted key.

[Joe Edwards]

Okay, thanks for the info. I figured the Indo models might be of lesser build quality after comparing my two calcs. Yes, the Singapore model is very quiet while the Indo model is almost as loud as a 49g+!!!

Joe