One of the joys of an itinerant existence comes in periodically being reunited with the fruits of various orders that were sent to hackerspaces or friends somewhere along the way. These anonymous parcels from afar hold an assortment of wonders, with the added element of anticipation that comes from forgetting exactly what had been ordered.
So it is with today’s subject, a Mustool MT525 electromagnetic radiation tester. At a cost not far above £10 ($13.70), this was an impulse purchase driven by curiosity; these devices claim to measure both magnetic and electric fields, but what do they really measure? My interest in these matters lies in the direction of radio, but I have never examined such an instrument. Time to subject it to the Hackaday treatment.
One of the most thrilling childhood toys for the adventurous 1970s or 1980s kid was probably the toy walkie-talkie. It didn’t matter that they were a very simple AM low-end-VHF radio with a range of about 500m and a Morse key of debatable utility, you could talk clandestinely with your friends, and be a more convincing spy, or commando, or whatever was the game of the moment. It’s a memory conjured up for grown-ups by [Chris G] with his ESP32 walkie-talkie, which replaces a shaky 49MHz connection with one a bit more robust through the magic of WiFi.
The hardware is a collection of modules on a custom PCB, aside from the ESP32 there’s an I2S microphone and I2S audio amplifier, which along with battery and speaker are housed in a neat 3D printed case. I2S is used for simplicity, but there is no reason why analogue components couldn’t be used with a few code changes. Connection is made via UDP over a WiFi network, or should there be no network via ESP-NOW. We’re not sure the range will be brilliant with those little on-board chip antennas, but with the wide range of 2.4GHz antennas to be had it’s likely a better result could easily be achieved if the stock item disappoints.
What do you do with a cool-looking misfit guitar that has non-working built-in effects and some iffy design aspects? Do you try to fix it and keep it original, or do you gut it and strut your stuff with new bits from around the shop? This is the conundrum that [Tim Sway] finds himself in with this late 70s/early 80s Formanta Solo II straight out of the USSR. (Video, embedded below.)
[Tim] likes a lot of things about it (and we do, too), especially the acid green pick guard, the sparkly pickups, and the beefy bridge that lets him set the string spacing individually, on the fly. It even has a built-in phaser and distortion, but those aren’t working and may never have worked that well at all.
The non-working effects guts.
As you can see in the video below, [Tim] has already spent a few hours making it playable and a little more palatable in order to figure out what to do with it electronics-wise. He started by making the 9 V compartment big enough to actually fit a battery inside, and drilled out bigger holes for new tuners.
Interestingly, these guitars had a 5-pin DIN receptacle instead of a 1/4″ jack. [Tim] bought an adapter just in case, but once someone dug up a schematic and sent it over, he decided to rewire it with a 1/4″.
For all of its plus sides, [Tim] doesn’t like the headstock on this thing at all and found the neck to be too chunky for the modern guitarist, so he cut down the headstock, shaved down the neck a bit, and stained it dark. He also made a new nut out of what looks like rosewood. Then it was on to the more standard stuff — file down the frets and polish them, oil the fretboard, and clean up the body.
The point of this exercise is to make a usable guitar for the modern musician. As [Tim] says, this is not a particularly valuable guitar, nor is it rare, and it wasn’t built that well to begin with. One of the issues is the switches — they’re kind of light and cheesy feeling, and one of them is directly in the strum path. Will [Tim] change those out but fix the original effects, or will he make the thing completely his own? We wait with bated breath.
