Frontier module repair tips

[spinchb]

Hi All,

A few weeks ago I posted a note that I was looking for a Frontier module. I subsequently posted a few pics of my dead one. I've decided I will try to fix it myself, but need a little guidance from you's.

Here's the links to that thread:

http://www.dwf.nu/viewtopic.php?t=4182

I was wondering if replacing the quartz crystal would be logical next step? Everything else looks passable. I have a donor NSC module that has corrosion that's screwed up the led traces. The display is quite fragmented, but it's telling time...albeit in an alien script

I'm wondering if the QC in the NSC is the same Hz as the Frontier module? Can I just pop it in there? Should I also swap the pot out? It has a bit of corrosion on it too.

Cheers,
Shawn

[spinchb]

Never mind. I swapped the crystal and pot. Crystal works on another watch fine. Still dead. Must be the IC is popped.

Shawn

[retroleds]

This article might be a good reference for you to check your technique against, since a Frontier module is the patient.
http://www.thedigitalwatch.com/Archives ... ip_002.htm

[spinchb]

Hi Ed,

Thanks for the link. I actually found that one in my prep before the operation. It was pretty straight forward. Though, I did break the tiny lead off one crystal. They are quite fragile. I had another crystal from a donor watch luckily.

I'm not sure where to take this one next. Someone before me had scraped the corrosion out with a knife. I wonder if they damaged the battery contacts on the board? Looks good enough. The resistor on the board seems ok. I hooked up a ohm meter to it and got some readings that confirmed it wasn't shorting out and had some plausible ohm value. Any other things anyone can think of to check? Seems to me it's toast.

Cheers,
Shawn

[Old Tom]

Ummm... What pot? (I presume you mean potentiometer or variable resistor). Cannot think of any 1970s LED watch that had a pot in. I think you are referring to the variable capacitor and this should have near infinite resistance if it is working properly (you have to remove it to check- cannot be measured in-circuit due to alternate current paths- don't even think about using a bridge type in-circuit tester, you will kill the main chip).

To test and diagnose any module I always start by measuring the current being taken from the batteries- 2-10 microamps (display off) is a good sign, 0-2 microamps usually means oscillator not running, higher currents means circuit board tracking or defunct segment/digit drivers. Next, probe the crystal with an osciloscope to see if it is actually running--- Think I ought to go away and write this up properly!