Re: i disassembled my 41cx, help! Message #2 Posted by Vieira, Luiz C. (Brazil) on 15 Nov 2002, 11:15 p.m., in response to message #1 by David E
Hi;
first of all, DON'T PANIC! Let's see what's going on.
You have the mainboard and the keyboard, so you have a fullnut HP41CX. What sort of connectors do you have between the mainboard and the keyboard? I know three different types of connectors and all of them go between these boards:
i - one of them consists of two tubular polymer and very-thin-trails zebra connectors built with an isolating sort of tape; ii - the other consists of a pair of foam with not-so-thin-trails zebra connectors around them; in this case, the plastic separator built in the screw posts has four extensions, to guide the foam so it stays in position iii - the last one resembles a conductive polymer, but it has a lot of thin conductors that once fold will hardly connect the boards.
Silly reasoning: in the last two cases, the conductors may be placed in a bad position OR rotated, what will not allow both main- and keyboard to connect with each other. Would you check for this, if you have not already done it?
Also, the "pressure" that keeps both PCB's and the connector between them comes from two different points in two different assembles:
i - one that has two big nuts around the screw posts; these nuts are directly "screwed" around the post itself, and keep enough pressure so both PCB's can "talk" to each other; ii - the other uses the case screws to keep the physical pressure that maintain the contact between the two PCB's.
The best assy, for me, is the first one, because the nuts will keep the calculator working even when the case screws are not completely screwed. In the second case, if the threads of the PCB's posts are loose and the screws are failing to keep pressure, the calculator will often have contact problems.
Taking care with the posts is the best we can do; checking for cracks or any fatigue signal. Many techniques to rebuild these threads and the posts themselves were described by the collaborators in here. You should give us some info so we can focus on your particular solution.
Also, you may read (if you haven't already) this article because it contains descriptions about how to disassemble and reassemble an HP41CX. The method of soldering the two PCB's is effective and should work, but trying to keep the connector between them allows faster PCB's trading, when necessary.
I know this is more information only, but I'm waiting for a more detailed description of your 41CX's internals.
Success.
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