Possible 503 module?

[Sully008]

Hello all,

I recently purchased the Pulsar 5503 that 1Tuna had on Ebay (yay!). The module in it has issues (2 digits no longer light up, but otherwise functional). So I replaced it with a new 502 module that I bought from Greg Ratcliff. What is interesting is the module I took out has what looks to be either a reed or mercury switch soldered to the side. Sadly, the switch is broken as well. I'm wondering if it's a rare 503 module? Would it be worth something to try and have repaired?

[retroleds]

It probably is Sully. The 502s are all set up for the flick-wrist function and the contact points are on the board, but getting a normally closed Mercury switch the right size is difficult. And dis-assembling the module to get to the contact points is not for the faint of heart(or wiggly of hand) as the entire circuit is exposed wire-bonds...only thing covering them is the other half of the module(i.e. the battery holder assembly).

[Sully008]

Hi Ed,

So I'm guessing getting this fixed is probably cost prohibitive? Too bad, it'll sit in my spare parts drawer for now.

[retroleds]

Real problem is finding a tilt switch that is nrmally closed, that is small enough for the space available. As you can surely attest, it is one small sucker....makes most reed switches look huge by comparison.

[Sully008]

Funny I googled "micro mercury switch" and came up with this:

http://www.freepatentsonline.com/3993882.html

That's the original patent for the switches used in LED watches.

"A micro-miniature mercury tilt-type inertia switch which may be utilized in a light-emitting, solid state, digital-display watch to activate a digital read-out circuit by a "flick-of-the-wrist" motion. The switch is normally in a closed position, i.e., a globule of mercury contacts both electrodes, and a tilt force of approximately 1.4 G's is required to open the circuit. A movement of the switch back to 2° or less below horizontal will reclose the circuit."

How about something like this:

http://www.signalquest.com/sq-sen-390.htm

Is 3.3mm x 6.9mm still too big for this application?

Real problem is finding a tilt switch that is nrmally closed, that is small enough for the space available. As you can surely attest, it is one small sucker....makes most reed switches look huge by comparison.

[retroleds]

It is a little fat in diameter, but the other caveat is, it would be awefully touchy. The original ones in the Pulsars are actually a magnetized mercury/iron droplet, that strongly tries to stay against the steel contacts. You can peel the silicone off the top of a Pulsar tilt switch, turn the switch upside down with a relaxed movement, and the ball of mercury will just hang there in mid-air, tight against the contacts. Takes a certain amount of "G" force to jar it loose - you know, that old "flick".. You actually will get the occasional P4 module that doesn't run correctly unless you give it a firm smack to jar the mercury loose, and it will work perfectly while kept upside down(mercury away from the contacts. Soon as the contact is closed it is back off. Programming is scrambled, time to remove the mercury switch and go "flick-less". Normally the action that activates a P4 or 503 is : switch is closed, switch is open for like 1/10 second or less, switch is back closed, display lights for 3 seconds.

A shame about the 503/502 module - they don't seem to fail often, but are difficult to repair. The "Pulse" has similar construction issues that limit repair-ability, IMO.

[bruce wegmann]

The switch in the 503 was a special size intended for this module only. It is much smaller than the one used in the P4-series modules [more like the size of the function switches on the Ladies' or Dress modules]. Since they use the same module, there may be a few Auto-Command Sports out there, too.