Re: [IC-7000] PTT Switch Failure
I took the defective switch apart and inspected it under a microscope to see why it failed. The switch has a snap action metal membrane that is slightly dome shaped. There are three contacts inside -- one lead connects to the top & bottom contacts which the circumference of the dome rests on. The other lead goes to the center contact which the center of the dome touches when the button is pushed. There are raised bumps on all three, which are intended to provide the point of contact and some wiping action between the surfaces.toggle quoted messageShow quoted text
There is clear evidence of wiping on the center contact and the dome. However, the bumps on the top & bottom contacts are set in too much and don't seem to touch the dome and there is no evidence of wiping action. The edges of the dome that line up with the contacts are heavily tarnished or discolored for some reason. This could result from elevated temperatures during soldering being transferred to the dome. The contacts were bright and clean. The leads are sealed adequately where they enter the body and there was no evidence of flux flowing along them inside the case.
Alps specifies that for manual soldering the temperature should not exceed 350C (662F) for 3 seconds. This is probably why we see so many cold solder joint problems on the PTT switch.
If you retouch the through-hole solder joints or replace the PTT switch in the mic, I would pay heed to this. My iron is 700 F and I probably exceeded 3 seconds when I reflowed the joint because the solder wouldn't wick up the plated-through hole to form a good fillet on the top side. Or the discoloration could have happened when I removed the switch with a solder sucker.
Also, the switch is not sealed, so you should not clean flux residue with flux remover or alcohol unless you are very careful. The factory's flux was still on the board, as was mine. Just use a known "no clean" flux solder.
--- In email@example.com, "Ivan Silva" <ivan@...> wrote: