Give your best hints for swapping P2&P3 and P4 displays

[azimuth_pl]

howdy,

I have one method that works best for me.
I usually cut the edge of the solder on a P2 or P3 display and then pop it.
once or twice however the display broke into pieces.

a P4 is a bit harder, especially a Sanyo type that usually has the entire board covered with some sort of epoxy/enamel.

any ideas welcome. would some heat applied to the surface with a torch improve the process?

[charger105]

I've never popped one off successfully. Only tried once on a thoroughly corroded P4(all the wire bonds had turned to dust !). The display broke into pieces.

Were they originally soldered on, or epoxied ? I assumed they had originally been epoxied on.

Rgds,
Andrew.

[bruce wegmann]

All Pulsar displays were soldered in position [the solder paste used in surface-mount applications melts at a much lower temperature than the alloy used in flow-soldering, about 275 degrees versus 600; P1s are soldered together with an indium alloy that melts at about 250]. The single component that was not was the light sensor...it was often installed with silver epoxy [most often on P2 and P3 modules, but occasionally on P4 and Dress watches, as well]. It is clear that they left the factory that way; there is no trace of solder on the circuit pads. As far as removing a display in the course of a repair, mechanical force is a workable but risky method. Better to selectively heat the part to be removed [I have a rectangular, funnel-like device I use to channel hot air from a paint stripper...it narrows down to just the size and shape of the display, and shields the surrounding parts from the 400-degree heat, gets the job done in 10-15 seconds]. OK if the display comes off in more than one piece; the one thing you DON"T want to have happen is to fracture the circuit board [it's a very brittle alumina ceramic]. You will immediately break circuit traces AND [on P4s and later models] wire-bonds, and such damage is essentially unrepairable.

[azimuth_pl]

thanks guys, although I could imagine a wider response

so far I didn't have a precise and small source of heat so I just bought a Dremel gas(torch) soldering iron with 6 different tips.
good idea with the cover to hide the rest of the components on the board.
I'll drink a beer and use the can to cut a proper size shield