HP 42S switches off immediately



#2

Hi I inherited a 42S and it switches off imediately after switching on. In some cases the display will flash for a split second, in other cases it doesn't show anything. If I press the ON key fast enough I can keep the display on until I release the key.

The self test (ON-LOG) works just fine, and passes OK. But at the end it just switches off. ON-ROOT (the reset function?) works and very briefly display "Machine Reset"

I can even adjust the contrast, and even get it to do calculations if I press a key fast enough at power on, but it switches back off again as before.

Anyone know what is wrong? Is there any higher level reset function I can try?

The batteries are brand new and tested.


#3

I saw one a lot like that on eBay recently. You might do a search, and contact the buyer, as he may have a solution.

#4

Looks like a very impatient auto power off functionality. A dead capacitor maybe?

#5

... the master clear procedure? Maybe it helps. Consider that everything stored in user memory is going to be lost, though.

Simply press and release three keys at the same time: [ON], [Sigma+] and [XEQ]. After releasing them, one message telling that all memory was cleared must be shown. If the calculator again flashes a message and turns itself off, then it may have other problems. I once found an HP41 with a bad capacitor showing this kind of behavior, but it has another design.

Hope you succeed.

Luiz (Brazil)

Edited: 28 Mar 2007, 11:05 a.m.

#6

Quote:
Hi I inherited a 42S and it switches off imediately after switching on. In some cases the display will flash for a split second, in other cases it doesn't show anything. If I press the ON key fast enough I can keep the display on until I release the key.

The self test (ON-LOG) works just fine, and passes OK. But at the end it just switches off. ON-ROOT (the reset function?) works and very briefly display "Machine Reset"

I can even adjust the contrast, and even get it to do calculations if I press a key fast enough at power on, but it switches back off again as before.

Anyone know what is wrong? Is there any higher level reset function I can try?

The batteries are brand new and tested.


Hey, that was my calculator on eBay, and your post is an identical one(cut'n'paste) to MY post on here a while back! :-P

If you are the guy that bought it from me then best of luck getting it fixed, all of the suggestions on this group and other groups did not fix the problem.

No it's not the capacitor(s), or other passive parts, it's not the batteries, and all the power-on reset and battery shorting tricks etc do not work.

If you do find a solution I'd be interested to know what it was.

Dave.


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