My HP-50G Blue dropped dead - The resurrection report

[Harald]

(01-28-2018 01:49 AM)jebem Wrote:  

(01-27-2018 11:21 PM)rprosperi Wrote:  Interesting observations that the assembly techniques are both manual and sloppy. Possibly this particular unit didn't pass the standard assembly QC checks and was reworked manually? It's hard to imagine these machines were made by the thousands every week, with such manual techniques.

Thank you for your feedback, Bob.

IMHO, the 50G has got two PCA's (the processor/keyboard and the display), and both were produced in an automated assembly line due to the components technology in use (SMD insertion is much faster done by a robot than by a human).

However the machine have several more components that are very old style (from the pre-SMD era), and these are manually soldered and routed and taped (battery holder, memory backup capacitor, power supply wires from the two battery holders to the PCA).

The connection of the two of the two PCA's could be automated, yes, but it was not in my unit. And I can guarantee is was untouched before me, because the RF shield was not broken. So I know this was a standard manufacturing procedure, at least for the batch where my unit came from.

Not that this is a problem by itself. A properly trained operator should be able to solder the interconnect 28 leads in less than 5 minutes including the solder flux removal.
One operator could make at least 80 assemblies per day without working too much.
If you need 1000 per day done, then hire 13 operators for this job. Nothing too much for a manufacturing plant.

Then the installation of the two PCA's inside the case:
- The two PCA's needs to be wrapped with the RF shield, temporally fixed with black tape, and then set on the final position in the upper case where a combination of screws and rivets are used to fix it, and this is a mix of manual processes and automation.

Finally the wiring and installation of the power supply components are clearly a manual procedure, using hard-wiring techniques, and taping the wires to fix them.

I don't see a problem manufacturing thousands of units per week using a mix of robotics and man power. This is what we have been doing along the years, not only in electronic devices but also in other areas like in automobile industry for example.

(01-27-2018 11:21 PM)rprosperi Wrote:  Does it seem feasible that the broken solder joint (broken upon the fall) was a result of poor assembly, or would a similar fall break such a joint if completed properly?

This was a manufacturing defect (cold solder joint), and the fall just triggered the open circuit. The problem would happen even without a fall, given enough time of normal usage (and normal use involves vibration, small "falls" when people put the machine on a desk resulting in some energy that needs to be absorbed as well).
We are talking about a solder joint that, if properly done, is very robust by nature.
The fall could have damaged the LCD itself (it was my fear, really), but that didn't happen because the plastic case is very well designed and built and have absorbed most of the energy.

Edit to add a link.
China assemblage line example where intensive man power (woman power in this case) is used to finish the calculators build.
https://www.google.pt/url?sa=t&source=we...OD4xbU2nov

The quality of solder joints has become worse since lead free solder is used. Lead free solder joints always look a little like cold joints. So it has become harder to check the quality of the joints.

Cheers,
Harald