I own an old HPS40 handheld scope, and I started to wonder if there are any differences between it and the newer HPS50, and it seems - there are almost none. Two most significant are LiIon charging circuit and USB communication module (which is missing from the service schematics available on-line). The rest of the hardware seems to be identical (although PCB is routed slightly different), and also the firmware seems to be the same.
I’ve also discovered that the HPS50 PC software works ok with the HPS40 - it doesn’t detect it, but still it is possible to type-in COM port name of HPS40 (the list is empty, nothing to select) and software will connect to it, and will be working just fine. Only option that doesn’t seem to work is the “native” screenshot (by holding Memory button on the scope).
I’ve had a serious problem to find an USB-RS232 converter compatible with HPS40, but finally I’ve found one (very expensive one - it costs ~11€) - it’s DIGITUS DA-70156 (FTDI232R based) made by ASSMANN. Most of cheap Chinese 2€ converters use CH340 or PL2303 chips, with a TTL inverter instead of a proper TTL to RS conversion circuit, so their HIGH level is 0V, and LOW level is 5V. Even the 5€ worth Unitek Y-105, although had a conversion circuit, but didn’t work well, because of about +/-7V levels under load. Only the Digitus one had a proper RS232 LOW level of 9V and HIGH level of -9V on ALL lines.