Post Reply 
HP48S strange behavior
06-29-2019, 08:45 PM
Post: #11
RE: HP48S strange behavior
Hi all,

Got the the calculator almost dismantled. I admit it's been a difficult work. Mine is one of those older ones from Singapore, as far as I can see engraved on the back cover. Iphones are much easier to dismantle! Wink

I have also removed the PCB. What a piece of art, my lord! All circuits there, are perfect. No problem at all in there.

So my only possible try is that "wash and dry" process for the keyboard. But I haven't find the way to remove the display.

How do you remove the display? Do you remove it together with the metallic frame? Or you someway disconnect the display itself? How?

If I'm able to remove the display, then I'll sink the complete keyboard into water. If not, I will maintain the display out of the water, as Geoff Quickfall explains.

Thanks for all your help!

Bst Rgds from Daniel

(06-28-2019 05:03 PM)BartDB Wrote:  Hi Daniel,

It could be that the battery leakage has got onto the electronics or worse into the keyboard.

Attached is a PDF of Han Duong's opening the HP-48 guide.


However, he uses a blunt metal tool, I usually use a plastic tool found in mobile phone repair kits:
Although they are prone to breaking I find they do less damage.


Once open, you'll have to undo the twist tabs to remove the PCB from the keyboard - the screen can be removed as well.

Check & clean the PCB. If the keyboard needs cleaning I suggest you not take it further apart as the plastic rivets are almost impossible to restore/replace. Instead I suggest you try the "wash and dry" procedure described by Geoff Quickfall (for a different calculator, but the principle is the same) in message #15 of this thread: https://www.hpmuseum.org/cgi-sys/cgiwrap...694#175788

As you have the calculator open, I suggest you replace the connector sponge. Just below the screen you will see the keyboard connector flex-pcb.

Underneath is a grey sponge strip that pushes it onto the main PCB. This sponge deteriorates and causes a bad connection. It is best to replace the sponge strip it while you can.

When re-attaching the PCB, the twist tabs have to be done up securely to prevent missing lines on the LCD (make sure the zebra strips and connections are squeaky clean). (doing this I always sweat a bit - the balance between doing it tightly and not breaking the tabs)
.
Find all posts by this user
Quote this message in a reply
Post Reply 


Messages In This Thread
HP48S strange behavior - Daniel Sole - 06-25-2019, 02:49 PM
RE: HP48S strange behavior - BartDB - 06-26-2019, 12:50 PM
RE: HP48S strange behavior - Daniel Sole - 06-26-2019, 01:41 PM
RE: HP48S strange behavior - mfleming - 06-26-2019, 02:31 PM
RE: HP48S strange behavior - Daniel Sole - 06-27-2019, 08:24 AM
RE: HP48S strange behavior - BartDB - 06-28-2019, 05:03 PM
RE: HP48S strange behavior - Brad Barton - 06-29-2019, 01:59 AM
RE: HP48S strange behavior - ijabbott - 06-29-2019, 09:20 AM
RE: HP48S strange behavior - BartDB - 07-04-2019, 01:06 PM
RE: HP48S strange behavior - Daniel Sole - 06-29-2019, 06:09 PM
RE: HP48S strange behavior - Daniel Sole - 06-29-2019 08:45 PM
RE: HP48S strange behavior - rprosperi - 06-29-2019, 09:45 PM
RE: HP48S strange behavior - BartDB - 07-04-2019, 01:02 PM
RE: HP48S strange behavior - mfleming - 06-29-2019, 02:51 PM
RE: HP48S strange behavior - Daniel Sole - 07-05-2019, 02:02 PM
RE: HP48S strange behavior - BartDB - 07-05-2019, 03:34 PM



User(s) browsing this thread: 1 Guest(s)