So this is really a quick update for some new discoveries. If anyone has a Victor V86p and found this page -- today is your lucky day.
Recently, I ordered another set of Stone Chinese Typewriter, Stone MS-1300 and MS-1301. They're dirty cheap -- 400 RMB for MS-1300 and 300 RMB for MS-1301, and probably another $30 for shipping. MS-1301 came last week, and MS-1300 is still in China waiting for shipment.
By looking at the schematics, I discovered something very interesting -- the machine should supports HDD (26-pin connector), but a model with HDD was never released. Considering Stone Co was never a hardware company (they heavily outsource hardware design and reuse machines in the Japanese market whenever possible), it's not hard to imaging that the machines was based on existing machines.
While researching the 26-pin HDD connector, someone told me it is a JVC proprietary connector. After digging around the Internet, I found that mattinx already reverse engineered the protocol to some extend . The machine almost looks identical!
Well, in fact, they should be the same machine. The motherboard looked pretty much the same, except that MS-1300 has a daughter-board (ISA board), containing Chinese fonts (mask rom) and word processor program.
The schematics of MS-1300 (or original Victor V86p) can be found under https://software-archive.tifan.la/Stone-Chinese-TypeWriter/eBook/ . 四通打字机电原理图 is the schematics (starting from page 232). 四通打字机原理与维修 is the service manual (starting from page 539). If the PSU is missing -- don't worry, the original PSU design is in it.
And what about the difference between MS-1300 and MS-1301? Well, MS-1301 looks more original. The processor is a NEC V20, the BIOS was written by Stone (Shenzhen8088 BIOS), but is still PC compatible (MS-DOS 3.30). The system is much more integrated, the battery is slightly better (2000mAh Ni-Cd), and supports 1.44MB floppy disks. Unfortunately, it no longer has external video port, nor external ISA expansion port. The keyboard was also slightly redesigned.