48S died



#3

Hi all:

My 48S went blank the other day. I thought it was the batteries but when I put in a fresh set (I checked that they are good) the screen is still blank.

If I press on the battery door I can sometimes get the screen to show some signs of life, but just for an instant.

Is it dead?

Even though I've owned it for about five years, it looks perfect and I don't want to throw it away.

Any ideas?

Thanks,

- Mike


#4

sounds to me like loose contacts. I'm not sure of the construction on one of these- I'm still a bit leery of taking one apart, but many HP calcs will have pressure connections for LCDs and if it gets loose, it goes blank.

try turning it on and typing 2000 <enter> 1 <enter> beep <enter> ?
(I really have no idea if it will beep with a loose LCD, but why not try?)

Christof

#5

Flip it over and remove the upper right rubber foot. You will see a small hole. Straighten a paper clip and poke it through the hole until it bottoms out. Remove the clip and try turning on the unit. You might be alive again, if so, you'll be presented with the question "Recover memory?" Answer no to clear memory and you should be okay.

If that doesn't do it, try pressing on the raised part of the bezel above the B and C keys while pressing the ON button. If it comes on, the keyboard circuit has lost contact with the logic board. It will need to be popped open and fixed. Post a message if you need help.

Good Luck


#6

Christof and Randy:

Thanks for the ideas. By the way, my calculator is a 48G (not S) sorry.

I tried all your ideas and nothing. When I put batteries back in it, the screen looked like a bar-code until I pressed the under-foot reset, then it went blank. Nothing
you recommended helped (or did anthing).

It might be a goner?

- Mike


#7

Hi, you guyts, Christof and Randy;

what do you think about a cold-sldering in one of the LCD drivers? There are two of them built beside the Saturn CPU, and I have seen electronic diaries with this sort of behavior. For funny (they do not cost so much, people throw them away and buy new ones) I repaired a few of them by cleaning the flat conductor or the polymer, but in two cases, there was a bad contact in some IC's terminals. Resoldering them was enough.

Just a hunch, what do you think?

Best regards.


#8

In the 48's I've opened, and there have been many, I've never seen a bad solder connection. I doubt it is a soldering problem, nor will a bad or loose LCD zebra connection cause the problem as described.

I suspect a bad power supply component on the logic board, for which the best repair is replacement. It is not worth the effort when you can buy new 48's on ebay for $50. I've seen used units without manuals go for $25.

Just my 0.02 worth.


#9

Hy, Randy;

thank you. This is a very important information. Can you specify the power components you have seen as bad? In this post our friend Philippe mentions a 1,000uF/6.3V capacitor in the 49G's power circuit that he found as burnt. I have an opened HP48G and I can see a capacitor with the same specs (is this the one that's burnt when batteries are placed wiht inverted poles?) and, in the opposite side, some SMD around what seems to be an inductor (in this MB, a "big" blue bubble). Are these the power-supply "team"?

Just to add more information about these beasts.

Thank you and best regards.

Luiz C. Vieira - Brazil


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