problem with HP-48SX


My 48SX is having an intermittant problem. As the machine has been discontinued, HP tech support will not address the issue. The machine is locking up and leaving the number "6" below the bottom register. This is to say (reading from the top of the display down, I see "4:", "3:", "2:", "1:", and "6". The only way to recover is to pull a battery out of the back. I've removed the upper right foot off and done several internal resets, and I've done the self tests described in the manual (all OK). I've also blown out the keyboard as best I could with canned air. Any other thoughts or solutions would be greatly appreciated. Thank you.



does the cursor (left-arrow) also appear beside the "6"? I few days ago, we had an HP41 with a stuck "5" key. I tested my HP48SX: if I press any numeric key and switch it ON, it comes like you said, with the cursor. Any other key will freeze the calculator. I did not remove the batteries, but it will come back to normal only after releasing the key.

The 41's awner said that a firm "rap" in the palm of his hand freed the key, and the calculator got back to normal opperation. Should you check for eventual battery leakage? These fluids are conductive, and I have a mylar 48's key-layer with some absent tracks because of this.

Hope it helps.




When the calculator locks up, there is no blinking arrow cursor beside the "6". The problem is intermittant (it happened twice last week) and I was tempted to give the machine a very firm "rap" up against the opposite wall.
:-) When the machine locks up, and I resort to pulling the battery, it asks me if I want to try to restore memory. I say "yes". It has generally been able to retrieve some of the memory, but eventually returns me to the same screen with the "6" and locks up again. I've checked the batteries as you suggested, and they aren't leaking. I generally go through a set of Mallory Duracells every three months or so, so they stay fairly fresh.

When it locks up again, I will try the "rap" against the palm. Do you know of any way to safely crack the case and clean out the area under the keypad? Like you, I'm suspecting a keypad plaque problem or some other keypad related issue as the self-tests come back OK when the calculator is working.

Thank you for you efforts and suggestions.


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