Davis VantagePro2 Weather Station Repair

Repairing some Davis Vantage Pro2 ISS trans­mit­ter boards that have stopped trans­mit­ting at night.

After notic­ing that my Vantage Pro2 weath­er sta­tion had stopped trans­mit­ting data for the past cou­ple nights, I replaced the CR123 bat­tery which did­n’t help with the loss of data the next night.
I decid­ed to open up the mod­ule on my work­bench to see if there were any issues. I already had a some sus­pi­cion of what might be caus­ing the problem.

After remov­ing the cov­er on the ISS it was quite appar­ent what the issue might be. The 10 Farad super­ca­pac­i­tor had sig­nif­i­cant amounts of cor­ro­sion on the leads con­nect­ing it to the board. Most of the board and com­po­nents have a weath­er resis­tant con­for­mal coat­ing on them, which makes it dif­fi­cult to sol­der and phys­i­cal­ly remove items such as the supercapacitor. 

The hard­est part for me was remov­ing the board from the hous­ing and reat­tach­ing it after the repair was com­plet­ed. There is a screw which attach­es the board to the anten­na brack­et, with a non-cap­tive nut on the back side. The board and anten­na brack­et can be rotat­ed about 35 degrees which allows access with a pair of nee­dle-nose pli­ers to hold the nut. Getting the screw start­ed in the nut dur­ing reassem­bly is a whole new lev­el of frustration.

After care­ful­ly scrap­ping the coat­ing away from the leads on the back of the board I was able to de-sol­der the con­nec­tions. And then after some care­ful cut­ting and pry­ing I was able to remove the NESSCAP brand super­ca­pac­i­tor from the board. The leads basi­cal­ly fell off the capac­i­tor with no force required.

I ordered some Vishay HVR ENYCAP ruggedi­zed 10 Farad super­ca­pac­i­tors that are rat­ed up to 3.0 volts from Digikey.

It is impor­tant not to induce any stress from the leads to the inter­nal capac­i­tor seals when installing the capac­i­tors. I used a thin pair of nee­dle-nose pli­ers to sup­port the leads next to the capac­i­tor and then bent the leads on the out­board side of the pli­ers. I also used sol­der­ing heat sink clips while sol­der­ing the leads to the board to reduce heat stress.

I used one of my bench pow­er sup­plies to pre-charge the capac­i­tor up to 2.2 volts with the sup­ply cur­rent lim­it­ed to 100 mA. This part is not nec­es­sary, but it was get­ting late in the day, and I want­ed to test that data was received that night and there would­n’t be much time for the solar pan­el on the unit to charge before dark.

That would nor­mal­ly be the end of the repair, as the unit worked fine over the next week.
But, I then received a call from a local friend who also had a new Davis Vantage Pro2 sta­tion that was under war­ran­ty, who was hav­ing the same issue.

They had called Davis tech­ni­cal sup­port about the issue, and after sev­er­al back and forth com­mu­ni­ca­tions with them, were told that it was like­ly a prob­lem with elec­tri­cal inter­fer­ence caus­ing the loss of data at night, and there was noth­ing they could do about it.

I had ordered two of the capac­i­tors for my repair, so quick­ly went over to look at my friends board.
There was no obvi­ous signs of cor­ro­sion and the capac­i­tor was a Maxwell brand­ed unit. A quick check showed that the capac­i­tor did have a charge.
I replaced the super­ca­pac­i­tor with the spare I had and added some elec­tri­cal grade sil­i­con sealant on the sol­dered con­nec­tions and between the capac­i­tor and the board.
After more frus­trat­ing reassem­bly the unit was ready to be pre-charged and reinstalled.

Even though there were no prob­lems with the orig­i­nal capac­i­tor, installing the new capac­i­tor solved the data loss at night issue with this ISS trans­mit­ter unit also.
My best guess is like­ly a bad sol­der joint between the capac­i­tor and the board.

As long as it works, that is what main­ly mat­ters.
I am a bit dis­ap­point­ed after doing some research that this was not cor­rect­ed by Davis tech­ni­cal sup­port, as it seems that this has been a known issue for over a decade.