Tanacom 750 Bull stopped working

[jeb]

So I have this Tanacom 750 Bull I have had for a couple years. Its one of the Japanese versions.

It stopped working a couple weeks ago. The backlight on the display is on, but no digits and the motor will not operate.

 Took it apart and squeezed the display (basically between the display and potting material) and it started working again.

I tried squeezing and shaking to get it to stop working...but it kept working. So last week took it out and of course its now not working again. Same back light on but no other functions working.


I would say because of how I squeeze the display that there's something in that circuit board behind the potting material where there's a crack in the circuit board or a bad solder joint or something.



Has anyone successfully taken one of these displays apart and scrape the potting material and was able to successfully fix this?


Or do I really need to find a replacement out of a boneyard and put a new display on this?


Thanks

J

[boon]

I tried to get one of the Shimano ones apart to fix one of the buttons, absolute debacle. If you wanted to de-pot it then there are chemical solutions that will do it for you, although if it's anything like the Shimano then the case is glued together as well.

[jeb]

Ok...so I got the board repaired. It was a simple cold solder joint. I have it circled in red.

Now I just need to reseal the board. It was actually just a plastic cover that was glued to the display cover. I have some potting epoxy I may use. I just hate to pot it...because it sucks taking that stuff off if I every have to get back in there again...

[jeb]

Here is the picture.

[boon]

Is that your board or just a picture from the internet?

A circuit board that changes behavior when you press on it is often caused by a dry or cracked solder joint. Pretty common in devices subject to impact/vibration, like a reel would be. If you examine it under a loupe or low power microscope they're usually fairly obvious; the other good way to find them can be a thermal imager or using freeze spray on small areas of the board. But most of these are specialist electronics repair equipment.