For those interested, here's a rundown of the different versions of the portable philicorda:
(original model released in 1963)
The most completely genuine tube-philicorda, using tube oscillators, preamps and amplification throughout. Neon-bulb dividers. The amp/speakers (AG7600) came in a separate rectangular wooden cabinet with a spring reverb unit contained in a plastic box under the case.
(released in 1966)
Re-design front panel, slightly larger case. The amp/speakers
are now mounted inside the organ case.
There were at least three different (sub-) versions of this model (though they were identical in appearance).
The first of these utilized tube oscillators, pre-amps & vibrato circuits and a mix of neon dividers and transistors for divide-down.
The biggest change came with the second version which except for the tube pre-amps/vibrato circuits used transistor oscillators and dividers
Finally the third and final version (introduced around 1968/69) was all-transistorized.
(unsure about the release date)
The GM752 was basically a fully transistorized 751 with 1-piece rocker switches instead of 2-piece push-buttons as used on earlier models.
Provided with an extra outlet for connection to an optional Philips rotating speaker cabinet.
"portable" (re-marketed as the "Penncrest" by J.C. Penney in the US and "Porta-Belle" in Sweden), circa 1968.
A sleeker more portable version of the GM751 without the amp/speaker.
Similar tube-preamp as the early 751 (though some units appear to have used transistor amps), case covered in blue tolex.
2-tone control panel and a cover that goes over the keyboard
from the front, tiltable metal stand that looks like 2 upside-down
(the last version of the portable Philicorda, introduced in 1972/73)
Re-designed front panel (now slanting): 4 horizontal sliders in place of the usual knobs.
Slightly flatter wooden case w/ metal cheekblocks. This model uses IC dividers and therefore does not sound quite as warm and organic as the older models.
"The (Yamaha) CS-80 is a step ahead in keyboard control, and a generation behind in digital control" -- Dan Wyman, Jan 1979