HP48G assistance request

[unixronin]

I have a HP48G graphing calculator on which the on/off/cancel button has gone very flaky.  It will no longer power on just by pressing on -- at minimum, a warm-start (on-c) is required; I can't power it off -- I have to wait for it to shut itself off; and I can't cancel operations or clear error messages.

HP no longer offers service on the HP48G, and it's pretty tough right now to justify the cost of replacing it with a HP48GII (around $110) or HP49G+ (around $150).  Does anyone know of a repair procedure for a flaky HP48G key (above and beyond the non-trivial problem of getting the never-intended-to-be-opened-after-manufacture case open)?

Comments

[ilcylic.livejournal.com]

No, and my HP48G doesn't work either, anymore.

So I have to make do with 'dc'. Which doesn't really cut it some of the time.

-Ogre

this may be too much info, if so just ignore me

[dustgrl.livejournal.com]

Never to be opened cases are usully either ultasonicly welded or glued shut. Both can be opened.

While wearing some nice thick workgloves. Take a hot air dryer and heat evenly around the seems.

Use a small very thin flatblade screw driver to pry the sides apart. If the sides are heating and soft but unpryable you may need to use an exacto knife to slice the weld.

I am not familiar with the 48G but most keyboards these days fall into a couple of easy to service cases.

Most consist of a conductive pad that presses down onto a circuit board. They tend to fail when oxidation (or just plain gunk) build up on the contacts patches of the circuit board. The easiest way to fix this is to take a pencil eraser and just erase that part of the circuit board.

In the case of mechanical keyswitches you can purchase any number of aerosol cleaners. Do not use TV Tuner cleaner. This was made back in the days of heavy clunky mechanical tuners and in addition to cleaning compunds contains lubricants.

Use the small straw sort of thing and ust shoot some into the mechanism of the keyswitch itself then work the switch a bunch.

Re: this may be too much info, if so just ignore me

[unixronin.livejournal.com]

As far as opening it, I have instructions on a procedure for opening the case from the rear, by entering the case through the IR panel and battery compartment to cut the plastic rivets, or from the front by carefully prying off the metal front cover and drilling them out. In either method, getting the case to stay closed again afterward is left as an exercise to the reader.

I've been pondering the merits of attempting one or the other. Worst case, I end up with an unusable HP48G; but I have a mostly unusable HP48G now, so I don't see that as much of a downside. The biggest logistical problem is that I have literally NOWHERE where (a) I have a clean, clear space to work on it, and (b) I have any guarantee that small fingers won't cause crucial small parts to disappear forever. Around here, the cat-toy rule applies -- "If it's not bolted down, it's a toy. If it can be pried loose, it wasn't bolted down."

Re: this may be too much info, if so just ignore me

[koyote.livejournal.com]

highly possible that it is a loose post. The post you'd have to pry apart to take the case apart, in fact.

try lightly climping down the bottom left edge of the calculator and see if the button works more reliably.

for repair services, possibly including trading out for a working unit, see www.hpmuseum.org message boards.

all else fails, I *can* fix, but it might take a while. Or trade me your 15C for one of the nice 48GX high contrast black LCD models :)


I assume you have 48X for windows/mac/*nix, fantastic emulator. I've also got some DOS runnable simulators for the 41 series.

Re: this may be too much info, if so just ignore me

[unixronin.livejournal.com]

highly possible that it is a loose post. The post you'd have to pry apart to take the case apart, in fact. try lightly climping down the bottom left edge of the calculator and see if the button works more reliably.

Hmmm, whaddayaknow ...... that does indeed seem to make a world of difference.

Assuming it's not merely behaving itself better today, any suggestions on how to make a more permanent repair? Any tips on how I get the metal front cover off without damaging it? If I can do that, I can probably fix the post....

Re: this may be too much info, if so just ignore me

[koyote.livejournal.com]

hrm,

I don't think it is so much a matter of removing the metal plate. IIRC (and I haven't taken apart a 48 series machine in a little while) the basic fix is from the back. it is even possible that a really really tiny amount of aerobic epoxy (superglue is anearobic and doesn't really work well for this, aside from discoloring plastics) syringed into the lower edge where the two halves meet and then clamped down overnight might do it.

Parsing that sentence should be fun :)

you obviously don't want to get anything into the electronics, but there is a lip where the two halves meet - you should have photos of what the casing looks like. If it's not clear, then don't do it, of course.

if you do go through the long and slow process of carefully taking the whole case apart, you might want to look at putting in one of the internal RAM upgrades. 512K internal will fit a LOT of data, including the *nix like OS (shellOS) and metakernel.

more is always available at www.hpcalc.org



www.hp48.org

Re: this may be too much info, if so just ignore me

[unixronin.livejournal.com]

Oh, and no, I don't have 48X ... and if I can't fix this (or maybe even if I can) I might very seriously consider that 15C-for-48GX trade. I very seldom use the 15C, truthfully.

Of course, I haven't really used my 48G in so long I've forgotten 90% of how to use it...

Re: this may be too much info, if so just ignore me

[koyote.livejournal.com]

not sure where to find 48X right now. It is a complete and truly fine emulator for most Xfree86 systems. google that one :)

a lot of good programming info is on the hpcalc website, too. But there is always the question of do you really want to get into it.