Cleaning a HP 48GX: Can I dip it in a solvent to clean?
#1

I have a HP 48 GX that I've not used particularly hard. The on key is variable in its function. I blew some air into the key area and have noted improvement with the function of the key...so was wondering if dust could be the culprit...if so...what is the best way to clean below the keys...can I dip the calculator in a solvent...batteries out of course...or does this require only compressed air.

Thanks,
David

#2

No solvents except distilled water! And that only after you've removed the batteries for at least a week to let the capacitor discharge. You will then have to wait several days for it to dry out. As for using compressed air, those little cans shouldn't hurt, but don't use true shop-type compressor air, it's way too powerful.

Last but not least, the cost of replacing your 48 is going up. eBay prices range about $300-$400, and Samson Cables now wants $999 for new-in-box old stock units. Just before the first HP49 came out, prices for a 48 dipped to about $100 at my old college bookstore...

#3

I wonder that I shouldn't just let the calculator discharge...when I whack it on the side in the palm of my hand...the ON button works...so I've considered some kind of static charge...or electrical issue...as well as dust. The ON button is working about 90% of the time after applying compressed air...I can always get it to turn on...it just takes more than one time occassionally.

I have seen a link to fixit.com...but for $78 dollars, I'd chip in the extra $50 to get the newest model...I'm not a collector.

Thanks for your help,
David

#4

A common problem, similar to your description, with the HP 48 has to do with an internal intermittant connection. Try putting some light pressure between the display and the softkey 'C' prior to depressing the 'ON' key. If this improves the situation, I have noticed someone claiming to be able to permanently repair that problem.

Good luck,

Brian

#5

Agreed, solvents are not what's needed here. But I could see some advantage to using a mild detergent soak followed by several rinses in DI. Carrying this all out in a sonicator might also help. If you have an oven with a "warm" setting, 90°F or so (verify this with a thermometer), you could let it air out for several hours.

Caps won't cause you any trouble as they will discharge during the process. If you're feeling paranoid you could discharge them with a piece of hookup wire, paperclip, etc.

Best of luck,

HDE

#6

Getting the new machine might be your best bet. The new HP49+ with serial numbers beyond CNA515... with ROM version 2.0 seem to be OK. The software of the 49 is far and away more powerful than the old 48. The computer algebra system, while not Mathematica, is darn good for a handheld. The new CPU seems like lightspeed compared the 48, which was quite slow for certain operations. If you do get a dud, HP seems to be good at warranty exchanges. Best of luck.

#7

Hi David,

I would (very strongly) advise against a "bath" in anything!

At some risk to the feel of the keys on some hp calcs
(e.g. 41) you can use CRC brand "Contact Cleaner" in minimal amounts.

It is very gentle but used on the older hp calcs like the 41 the keys lose their tactile feedback quality when the spray is applied.
As the plastic components "dry out" (rapidly!) some of this tactile feedback characteristic recovers. At least the keys then operate!
They feel a little spongy, though and don't make a clicking sound.
A small price to pay for a functional keyboard.

Never use any detergents at all (!). If you want to run a small
*risk and use ultrasonic cleaning in a fluid (I don't have access to such exotic stuff!) the only liquid to use is isopropyl alcohol.
Distilled water sounds okay, but metal can be induced to oxidize.
At least isopropanol is as inert as you are going to get.

*If liquid permeates between the LCD interconnects to a PCB, then often you will lose the display (connections).

For What Its Worth...

DW



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