|Re: HP11C repair|
Message #2 Posted by Vieira, Luiz C. (Brazil) on 13 May 2002, 9:50 a.m.,
in response to message #1 by Charles Galloway
The voyagers (10-series, say, 10C, 11C, 12C, 16C and 16C) have two different internals: the first series had a separate flex-PCB with all IC's plus LCD, and a separate keyboard. The second production offered a single all-built-in PCB, with IC's, LCD and keyboard. I have a non-operating (for now; I'll find the time to go for it) HP15C and another full-operative unit, both different. It is easier to repair the earlier models, but as it seems you have some problem with the keyboard, it would be hard in both cases.
You can open the unit by unscrewing four screws under the four rubber feet. PLEASE, take care with two small springs inside the calculator. They keep contact between both aluminum plates (decorative and keyboard labels) and the bottom plate (general information). They are for ESD protection and must be safely stored (one beside batteries compartment and the other at the lower right, between third and fourth rows).
If there is only one big PCB from top to bottom, yours is a new model; if there is a separate assy under (built under) the LCD, yours is an earlier model. In the second case, you can remove the IC's/LCD assy and check if there is any sort of dust between the assy and the keyboard's PCB. (PLEASE, also take care with 8 (eight) small shock-absorber foams; the LCD assy is built on four posts, and there are 2 foams for each, top and bottom. Keep them in a safe place.) There is a small conductive foam between the assy and the keyboard.
If yours is a new type, you should check if there is anything wrong with the rightmost IC: this one reads the keyboard, and I have once replaced a 16C's for an 11C's (they were the same in those units). If you believe you'll have to look at the other side of the PCB to check for problems, then there is a big job ahead: removing it. All plastic posts are used to retain the PCB, so they all must be carefully worked. After that, removing the PCB is easy (lookout for the keys...).
Well, cleaning the unit's guts is the next step. Let us know if you are getting success for now.
(PLEASE, FALKS! Allow me to write in a better way. If there is something written in here that is wrong or could be better expressed, let me know. I usually learn fast... Thanks.)