HP 71b repair advice - won't power on with batteries or on AC adaptor

[KimH]

(06-15-2021 06:18 AM)dmh Wrote:  

(06-11-2021 03:35 PM)Dave Frederickson Wrote:  Another cost savings with regard to the plastic-backed 71's is rather than using heavy metal shielding, the inside of the case is sprayed with a silver-colored metallic coating.
In the photos it can be seen that this coating has been attacked by the corrosion and is flaking off.

The PCB's can easily be separated from the case halves after the two wires to the beeper have been desoldered. Remove as much of the flaking metallic coating as possible.

Dave

I can't see how the PCB's can be easily separated. The top looks plastic riveted and the bottom, although it looks like it is just sitting on plastic posts, doesn't want to move at all. Are the Zebra posts part of the lower case and holding the PCB down? As mentioned, Zebra doesn't appear to want to move either.

Any further guidance you can provide?

Thanks

That is a hard one without having the PCBs in front of me.

The "Top" PCB with the Display/KBD is what it is - risky to mess with and most likely not the cause of a malfunction unless the connectors to the LCD inside the Welded construct OR the KBD (an issue I for sure have seen) has been attacked by some chemical/fume. This could be tested with a good "Bottom", but that is not available to you.

The "bottom" PCB - once the Flange holding the Zebra is out - can be gently pulled out of the front Module ports - lifting the PCB part up-away-and-out from the ports ever so slightly. Again this is hard to judge unless having the possibility to handle the PCB. Force is not required for this.

The story about the Solder Joints going "black and hard" I have not experienced with a 71B, but I have with other products, it simply won't budge without destroying whatever it is soldered onto.