Tandy TRS-80 Model 4

I thought I knew most of the HP calculators, but I can't think of one that's called the 'Programmer'. The nearest would be the HP16C (codename 'Pr' IIRC) which is the 'Voyager' series machine designed for low-level programemrs with boolean operations, shifts/rotates, etc. One currently resides on my eelctronics bench. If it _is_ a 16C, then the keyboard uses metal dome swtiches, not conductive rubber. I also recoemnd against dismandling it, the keyboard PCB [1] is heat-staked to the top case and it's difficult to get back securely if you take it out. [1] Early Voyagers have a conventional PCB heat-staked to the top case containing jyst the keyboard and a separate module fixed ot the dispaly built on a flexible PCB that carries th 2 chips [2]. later models have everythin on the one, conventional, PCB. Incidentally, dry-joints on the pins of the chips are not too uncommon, I've got serveral Voyagers going again by resoldering the chips [2] THese are NUT (the smaller chip, CPU and keyboard interface) and R2D2 (the larger chip, the neame is an acronym for ROM/RAM/Display Driver) -tony