Odd factory mod on TRS-80 26-3612 (Sharp CE-158) RS232 interface

[Jeff_Birt]

I don't think this mod is related to the PC-1600 but it is a good idea. Firstly, the 26-3612 was introduced and phased out long before the PC-1600 was available. Secondly it seems that this mod was only done on the TRS-80 version. The PC-1600 also has RS-232 built in, but I suspect it might be able to use the CE-158 as well. The mod wires are also on the DB25 side, not the 60-pin connector side.

I have not looked very closely for differences in the 60-pin expansion connector. Sharp did make a few mistakes in the pinout diagram in the PC-1500 technical manual. The PV and PU pins are swapped in the pinout and one Vcc pin is mislabeled as frame ground. There are a few unused pins on the PC-1500 that they might have used on the PC-1600.