Repair of BirdRF 3171 Wattcher for WCGQ-FM – September 16, 2021

The BirdRF model 3171 Wattcher used by WCGQ-FM had failed. After major equipment additions, and rearranging of the ABS, LLC repair lab, I finally got a chance to sit down at the workbench and repair the Wattcher, which was completely dead.

Overhead view of the inner working of the BirdRF model 3171 Wattcher with the top cover removed.
I found the MC7912CT -12V regulator had failed. It appeared to have been replaced before, and I found some circuit trace and solder pad damage.
The 10 uF tantalum capacitor on the output of the -12V regulator was short-circuited. This was the reason the regulator failed.
The thru-hole solder pads and circuit traces associated with the -12V regulator (component designation “U03” on the circuit board) had considerable damage.
This is how the opposite side of the board looked like before removing any components or doing any trace and pad repairs or cleanup.
By scraping back some solder mask, bending two of the leads on the replacement -12V regulator, and flowing solder between the leads and circuit board traces, I was able to achieve a solid “surface mount” style contact for those leads. The original thru-hole pads were not a necessity as they don’t actually connect to anything on the opposite side of the board. They were simply there to make routine thru-hole type soldering possible during the manufacturing process. I replaced the failed tantalum capacitor with a high quality electrolytic. An electrolytic isn’t as stable or long-lived as a good tantalum capacitor, but it will work fine for at least a few years. Plans are to switch over to a different model BirdRF Wattcher for WCGQ-FM, so extremely long life should not be an issue anyway.

This is how the opposite side of the circuit board looked AFTER cleanup, some trace repairs, and installation of the replacement voltage regulator and capacitor. As you can see in the photo, I had to scrape back some solder mask where one end of the replacement capacitor was installed and bend and “flow” the solder for the lead to the circuit board trace. This was because the heat of desoldering damaged one of the solder pads. I can’t blame that one on anyone except myself — along with the solder pad not actually being a plated, thru-hole type. In that situation, a solder pad sometimes simply can’t take as much heat as is needed to remove the original, high silver / low or no-lead solder.
The 3171 BirdRF Wattcher came back to life following the repair work and appears to be working properly. It is ready to be put back in service.