Want to know what that “blind” power supply is putting out? Adding a digital volt/ammeter to my old meterless Astron RS20A power supply was actually quite easy, though the metal fabrication took a bit of time.
This supply was purchased on our honeymoon in 1990 from a shop in Vancouver, and was “on” for just about the entire 24 years since. It began to give up on me earlier this year. Despite being rated for 16A, it has been running a 20A transceiver for years, only now saying “nope, I can’t do this any more.” I purchased an Astron switching supply (30 amp) to replace the old unmetered supply.
I replaced the voltage regulator chip on the RS20A, and it’s working nicely once again, but I wanted to be able to monitor its output now that it is being retired power only the auxiliary gear in the shack — DX Doubler, the antenna tuner meter lighting, a noise-cancelling box, and the control boxes for my 80M and 40M switchable arrays.
The meter was purchased on Amazon.ca for $19 including shipping (try this one — cheaper and with free shipping), and arrived in two weeks from Hong Kong. I actually ordered one with red LEDs for voltage and blue LEDs for current but received a meter with red for both — the vendor is sending me the correct meter at no charge, so I’ll retrofit that one when it arrives.
Wiring it up was a simple process, though cutting the front panel with the Dremel tool and finding a suitable place for the shunt in the back of the box took about three hours of focused effort. The meter reads very accurately, according to my Fluke meter as a reference. I am pleased with the look and operation of the project.
While I was at it, I replaced the old power switch (neon bulb had died years ago) with a new one purchased for $7 from Home Depot. Direct swap-in dimension-wise, but the pin-outs for the new switch were reversed from the factory original. I discovered this my blowing the 5-amp line fuse. Three times. Slow learner here.
Total cost: $20
Time: about 4 hours