The trickiest moment in this build came at the amplifier board. Getting the TPA3116 to run mono by soldering strapping wire onto the tiny HTSSOP pins went badly, and the maker recovered by bridging the plus and minus connections downstream of the filter instead. That strikes me as a smart recovery when fine-pitch work turns against you.
The donor was a 1950s General Electric T-126A AM set, picked up broken on eBay for $49 shipped and dated 1958 to 1962. The tube board and speaker came out, the housing got a wash with soap and water, and a hole went through the rear cardboard panel for the DC barrel jack. After soldering the power wiring, the maker installed a MarkAudio Pluvia Seven HD 4-inch full-range driver, the ZK-502C Bluetooth 5.0 board, a 24V 5A adapter and a two-color printed chassis bracket with brass threaded inserts. Around $160 all in, and it became a wedding present for the maker's brother.
The detail I keep coming back to is the sheet metal plate that adapts the driver to the original mounting points. It was drawn in CAD, cut on a CNC plasma machine over a water table, then spray-painted black. The original tuner knob was reworked slightly to seat properly on the amplifier board, the volume potentiometer hides behind the stock knob position, and the 3.5mm input sits in a single perforated hole at the rear. Keeping the front looking period-correct while everything behind it is new seems like the right call to me.
One trade-off remains: the old on/off volume knob is dead, and the AM tuner knob now handles power and volume together; the maker called a separate power control redundant. The original tubes are still kept, and the CAD software behind the plate was never named. The maker rates the finished unit as sounding pretty good.
Project by Mad Man Machines. Watch it on their YouTube channel: