Simrad WR20 Battery Replacement and Charging

As discussed in the previous (Dutch) post my WR20 did not charge anymore. We had a replacement battery on order with Simrad, but after a year they still do not know if and when a new battery will be supplied.

I decided it was time to open the unit, after all, 30 years ago I did quite a bit of soldering myself. Two things were immediately obvious: the inside looked brand new and was totally clean. No dust or rust, the sealing had worked very well. The other thing was that there was a loose part in the unit, a (skottky) diode. Disturbing, but also hopeful. If I can find where the diode belongs, it might explain why the unit did not charge any more. The battery might be just fine.

Missing Diode

Missing Diode

As the picture shows with a red oval, there is indeed an empty spot. And the chip nearby has a number: 400242. This is a charger chip, and the diode provides the power to the charger. So this tells me (1) how the diode needs to be mounted, and (2) that the battery could not charge anymore.

So the diode needs to be re-soldered as shown below. Be careful not to overheat the circuit board or diode, you need to use a very small soldering iron!

Diode Mounting Direction

Diode Mounting Direction

When reassembling the remote, be sure that the springs for the charging contacts are properly mounted. If you want to test the unit away from the boat: the charger has the plus 12V (+) on the left hand side, and the ground (-) on the right. This is facing the wall-charger contacts, not the WR20.

When tried mine after the repair everything worked fine again; it charges and shows the instrument data again.

WR20 charging again

WR20 charging again

I would not be surprised when a good portion of the WR20s that do not charge anymore suffer from this very same problem. The diode did not seem to be mounted very well, it was just pressed in a bit of soldering tin, with no pins through the circuit board.

Please let me know if anybody uses this post to revive his Simrad WR20.

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