Dead segment in P3 LED display

[spinchb]

Hi All,

My project P3 is coming along. I replaced the QC with a oscillator IC and now it's keeping time. However, there is 1 dead segment in the 2nd from right digit. Am I right in assuming that that this is a dead LED and I need to replace the whole display? If it was the same segment in all digits, it would be a transistor problem, correct? Is this something easily repairable?

Thanks for any advice! It won't go to waste.

Cheers,
Shawn

[bruce wegmann]

Sounds like you have a broken wire bond in the display. Only remedy here is to remove the display from the module and do a transplant from another circuit board. It's the removal process that's the nail-biter; it takes a fair amount of force to break the display loose... You might want to practice getting the display off a potential donor board or two before working on the newly-revived one. No question; it's a risky procedure. But, I have successfully done a couple of these, so I know it can be done.

[spinchb]

Hi Bruce,

Thanks for the confirmation. This is turning into quite the project.

Anyone out there have a working display they want to sell?

This module also has a problem with the reed switches. The magnets on the buttons are too strong for the switches. They often fire off without touching them. What's the easiest way to lower the amount of magnetism reaching the switches? Moving the switches? or is there a way to put something in front of the switches to reduce the magnetic force reaching them? Or, both methods?

Cheers,
Shawn

[bruce wegmann]

Overly-sensitive reeds are not difficult to correct. What you need here is what Time Computer called a "high-mu shunt". It's a little strip of a high-nickel alloy steel that is bonded to the inside of the button cover. It has the effect of diverting part of the button's magnetic field, effectively reducing it's strength. Ideallly, the switch should close when the button is about three-quarters of the way through its' range of travel, preventing gentle touches or even light bumps from accidentally activating the display. The amount of transmitted magnetic field can be adjusted by changing the size or location of the shunt. Altering the original position of the switch is risky, may result in breakage, and should be a last resort short of actually replacing the switch (where you may encounter a whole new set of problems). I have a good number of pieces of shunt material available if you want to try this method.

[spinchb]

Hi Bruce,

Thanks for the information! I would be very grateful to get my hands on a few pieces of this shunting material. I'll message you directly about this.

The other issue is the setting magnet isn't working through the case. I guess it has weakened over the years. Are there remedies for that? Putting it against another stronger magnet for awhile to magnetize it again?

Sorry for the newbie Pulsar repair questions. I get smarter everyday.

Cheers,
Shawn