- 2026
- Jan
- 15
Checking out some recent acquisitions - #3 - Radio Shack Lives!
Well, it’s a zombie, but whatever.
Here’s a couple of devices I’ve picked up at shows and other places, both branded “Micronta.” The first is a small DVM that’s in a calculator-style case with old bubble LED displays. It’s a model as soon as I remember to look at that I’ll put that model number here.
Apparently, this is a clone/rebadge/rework of the Sinclair PDM-35, which came in a white case.
The back has a very dirty on/off switch and a jack for a power adapter. I think that’s one of those old 3/32” phone plugs that companies loved to use before coaxial barrels became popular.
It requires a 9V battery. Let’s slap one in and measure some volts.
The decimal point doesn’t move - you’re required to move it in your head.
The device’s big brother doesn’t really agree with the measurement. It’s close, however. How about some ohms? Like 330 of them?
Big brother really doesn’t agree here.
Eh, I guess for a dollar hamfest buy, we’re lucky it works at all!
The next device is another Micronta unit, also in some sort of calculator case. This is a Model 351 Counter, catalog number 22-351. Made for Radio Shack, of course.
It comes with a manual, case, and antenna.
They simply used a standoff inside the case as a mounting point for the antenna, which itself is just a piece of chrome plated screw rod. Cost savings everywhere!
The battery compartment on this one is clean, but the battery connector itself needs some love. It broke shortly after this test, so I need to find some new ones. It’s been years since I needed some 9V snaps.
It uses the same 3/32” phone plug for power, has a screw standoff for the antenna, and a 1/4” phone jack for signal input. I have a phone plug on some clips I use for troubleshooting, so let’s slap a battery in and connect it to a signal generator. I give it about 5KHz, which should be well in the range of this device.
And…nothing other than two dots. I get some numbers rolling around when inserting or removing the plug, so the device is probably counting when triggered - but isn’t triggering.
Inside is a simple circuit - some glue, a big 6 decade upcounter IC, and some chips.
Yes, that is a National Semiconductor logo there…they made the display board, which the manufacturer of this device just purchased whole.
I plan on doing some checks on this thing, starting with the oscillator - but not today. This goes in the pile for later.
Stay tuned!
Next part of this series: Coming sometime.
Previous part of this series: https://wereboar.com … -ps120-oscilloscope/