Opening the HP-71B



#8

I need to open my HP-71B because it works perfectly on ac power but does not work using batteries. I believe the springs or contacts from the batteries inside the case have separated. I have searched for the mechanical drawings or other information in the HP-71B documentation on the MoHPC DVD with no success. How do I open the HP-71B without causing any damage? Thanks for you help. John Pierce


#9

Hi, John;

I openned mine once for checking purposes, and I found no problems separating half cases after removing (a bunch of) screws. I am not sure if there are screws under the rubber feet, but I think it's worth checking it, too.

On the other hand, I had some doubts about openning the HP75D because I felt some mechanical resistence on separating both halves after removing all screws (a bunch, too). After some reasoning, I forced it a bit and heard a loud 'cracking' sound. Fortunately it was super glue. I think that someone opened it and glued it back, but I am almost sure it was not any HP guy. As it has an AT&T label, I guess AT&T tech personal decided to glue the halves to avoid the computer to be inadvertently opened by other curious people... like me!

If you find yourself in trouble, I can take som epictures showing my HP71B opened.

Cheers.

Luiz (brazil)


#10

Thanks for you kind reply. I should have noted that the HP-71B is the "old" style with the metal back which has three small screws showing. Should I check for screws under the rubber feet first?


#11

Hi, John;

I'll be home in about two hours and I'll check for screws under the rubber feet. IIRC, there is one (or there are two) scres inside the battery compartment as well (if not, this is in the HP75D, sorry).

'See' yah in a couple of hours...

Luiz (Brazil)

#12

Hi, John;

I checked the HP71B right now an it has:

one screw under each rubber feet; (except for the rubber feet in the cover of the card reader compartment)

three screws inside the battery compartment;

one screw inside the compartment used by the card-reader (empty if none).

If I did not miss any, there's a total of seven small screws to unscrew. Another fact: take care when screwing them back after closing the HP71B; the thread in the plastic tends to get loose if you miss it and force the screw driver.

Thh picture below shows the back side of the HP71B with the locations of the screws.

Hope this helps.

Cheers.

Luiz (Brazil)


#13

Your picture is worth at least ten thousand words. Thanks Luiz you made my life a lot easier. Best regards, John PIerce

#14

You mentioned in another message that it was the old-style one...

In that case, remove the card reader port cover, the battery cover, and batteries. Peel off the 3 feet remaining on the machine. Undo the 2 tiny screws close together near the edge of the machine -- LEAVE THE OTHER ONE ALONE. Undo the 5 TX6 screws (one in the battery compartment, one in the card reader compartment, one under each of the feet you removed.

Carefully separate the case halves. On old machines like this one, they're linked by a flexible PCB that you must take care of. Don't just yank the case apart. If you mangle that flexible PCB you have a long day ahead of you replacing it with ribbon cable.

I can't remember quite how the battery and AC adapter are connected (but there's a schematic on the MoHPC CD-ROM in the hardware IDS). Most likely there's a diode in series with the +ve terminal of the battery, and a bridge rectifier on the AC input. All standard parts that are easy to check and replace


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