[SiriusHardware]

You can now get SMPSU modules which have roughly the same form factor as a 7805 regulator and the same three-lead pinout, obviously they are a lot more efficient and don't require a heatsink for the same power out.

My official Raspberry Pi 4 PSU unit (5.1V) has a USB-C plug on the end and is allegedly capable of supplying 3A, but that might be subject to intelligent negotiation between the PSU and the thing being powered. My original MK14 with all onboard options fitted draws about 0.5A from 5V.

I would hesitate to power something as ancient as an original MK14 from any mains SMPSU which does not have its 0V-out connected to mains earth via a metal pin - un-earthed mains SMPSUs often have low current high voltage AC superimposed on their 0V line due to the use of a low value capacitor across the mains / low voltage barrier, for EMC suppression purposes.

That low current high voltage won't hurt me if I happen to touch the 0V of the circuit being powered - at worst an unpleasant tingle, but that same tingle could be the death of old ICs - hence my obsession for interfacing with the MK14 via optocouplers whenever possible.

Getting back to the tape loader, it occurs to me that if we were prepared to change several (timing) bytes in the 'new OS' code we could 'speed load' cassette code in from the various digital devices we can now use to directly generate the digital waveform the SC/MP expects to see on Sin / SenseB.

Or going halfway: Use the in-PROM cassette routines to load the software tape loader routine (from the manual) with modified (faster) timing into spare memory at normal speed and then use that to load your code in from the ESP32 at much higher speed. Obviously the ESP32 would have to output the data at the corresponding higher speed. You could make it automatically send the speed loader code to the MK14 at normal speed and all other files at much higher speed on the assumption that the already loaded 'speed loader' code will be used to load those.