HR92 blank display after batteries went flat over summer

[neutronwrangler]

This has happened to three of my valves. They are in hard to reach places so I left replacing batteries until now.

On changing batteries the displays have remained blank. I've checked the contacts and they are clean, top and bottom.

Is there an internal charge storage that needs to be replenished? I have left them with new batteries in for several hours, but so far nothing has happened.

Alternatively is there a hidden reset switch that will get me out of this?


John Cooper

[neutronwrangler]

Solved

I've found out, by dismantling one (see YouTube for how https://www.youtube.com/watch?v=uBGRc8XpOZI) that there is invisible corrosion on the lower contacts. By scraping with a screwdriver I have removed it and have increased the bend in the contacts by pushing up on the central springs from below, thus increasing the pressure and maybe changing the contact footprint. I think for the future I will take a dowel of the same diameter as an AA and stick some fine emery on the end, then a few rotations will be enough to clear them.

[Richard]

Solved

I've found out, by dismantling one (see YouTube for how https://www.youtube.com/watch?v=uBGRc8XpOZI) that there is invisible corrosion on the lower contacts. By scraping with a screwdriver I have removed it and have increased the bend in the contacts by pushing up on the central springs from below, thus increasing the pressure and maybe changing the contact footprint. I think for the future I will take a dowel of the same diameter as an AA and stick some fine emery on the end, then a few rotations will be enough to clear them.

Thanks for posting. But yes, normally corrosion on the battery contacts is the only fail point on HR91/HR92 as they are pretty robust.