LCD screen fade on HP-11C



#9

For 19 years I have been consistently thrashing my 11C with engineering work and suddenly the screen has faded to the point of nearly indecipherable. It's not the batteries as these were replaced a couple of months ago. I have absolutely no wish to lose my robust work partner. Any ideas?


#10


#11

Does '(nt)' mean not telling?


#12

and "Luiz" is Luiz Vieira, an active and very helpful regular of this forum.

Regards,


Bill

#13

Perhaps he is enjoying holydays. Wait for him and ask him because he knows very well the voyagers.

Regards

Raul

#14

Hi Brett, folks;

thanks for your kind mentioning, guys! I'm flattered... :)

I'm just doing some "homework" and spare time is about nothing... Last time I read messages here was about a couple of days ago... shame on me! (B^(

About the Voyagers: I've actually had successful experiences repairing some units and rebuilding others, but there are some brainy guys in here that know them 'in deep'. As you mentioned wisely, Brett, they are robust work partners, indeed.

Depending on your partner "age", your HP11C has one of two internal assemblies. The earlier units had a separate "logic" assy with all electronics: two SMT IC's, the LCD and three passive components. Except for the LCD, all of these are soldered in a flex PCB and are "locked" with the LCD with eight tabs (2×4) that are part of the LCD frame. This assembly "connects" to the keyboard PCB by a small multiway, conductive polymer. I have an HP16C that has this earlier assembly type, so all other Voyagers have this earlier assembly as well because the HP16C and the HP10C were the last ones to be introduced. The images below are from the MoHPC and show the earlier assemblies.




This one is mine:

Later units have a single main PCB with all components either soldered or connected to it (LCD). Although the earlier types allow cleaning and repairing easily, I had no good experience with an HP15C with corroded copper trails. I prefer not messing too much with these earlier units. On the other hand, the later assemblies allow no LCD repair or contact cleaning unless you remove the entire PCB. Some guys have removed the front aluminum bezel, but I'd rather not trying this sort of maneuver as well. If it bents (and it is more likely that it will...) I know it is hard to smooth it back and remove wrinkle marks. These images were generated with a flatbed scanner (I have no photographic camera...)


These are from the newer HP12C made in Malaysia.


In any case, there are two possible solutions: re-soldering the IC's terminals (not hard to accomplish, needs just basic skills and ESD care) and/or cleaning the LCD polymers and contact surfaces. I've done both many times and I succeed in all of them. Except for the HP15C mentioned above, that had its flex PCB damaged but I managed to rebuilt all of the HP15C electronics successfully in an old HP11C PCB.

As you have already noticed (perhaps when reading), I'm a Brazilian and I'd like to help. I have some other calculators from friends waiting for final care (M.B., J.G... thanks for your patience...)but I am confident that I'll find the time to resume their repair in this vacation. At least I hope so... I am also sure there are other guys closer to you that would help you as well, but I'd be glad having the chance to help. I'm "chasing" more images of disassembled Voyagers that would help you or anyone you know that could try repairing it. As soon as I find them I'm posting another message, O.K.?

Success!

Luiz C. Vieira - Brazil

Edited: 15 July 2004, 1:21 a.m.


#15

Hi, Luiz!

I have other pictures from my Voyagers. I'll manage to send to you when I get home (I'm working now on the UFPR as System's Analist).
I have from my old 15C and 11C, and I have now a "semi-dead" 11C to play with.

Best regards,

Nelson


#16

Hi, Nelson;

Valeu! Brigadão! (thank you very much)

I'll save them with the others I have. I am not sure if I sent you some images sometime ago; did I? If not, let me know and I'll send them. Have you seen that the two HP12C have different PCB layout? I scanned these from another Brazilian contributor. Let me know if I can "show" them when needed, your name mentioned anytime it happens, of course.

Best regards!

Luiz

Edited: 17 July 2004, 1:02 a.m.


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