The 1640A as found: grubby, but with the whole keypad and the LINE switch intact. The sticker above it still says Learjet Inc, Engineering Lab, reference only.
The machine was dirty but quite complete.
Internals
Inside, seen from the top: the linear supply and its transformer down the left, the card cage on the right, and the CRT below.
The power supply is a linear one and has some nice large elco’s:
One of the supply cans up close, a Sprague 673D133, 3300uF at 6.3V.
These were removed and tested, and all of them tested fine. I removed them and reformed them for 8 hours so that they get used to being under power again.
The 01640-66502 power supply board, with its fuses along the bottom edge and the +15 ADJUST pot at the top right.
The card cage pulled out on its slides, four boards deep, with the analog board standing at the back.
The 01640-66516 microprocessor board. The AM9080 sits at the left, next to an 8228 bus controller, with a row of empty ROM sockets across the middle.
The 01640-66504 interface board: an 8255A, an 8253 timer and two 8251A USARTs, with the blue Clare relay at the top.
The 01640-66505 display processor, another 8008-era board, this one built almost entirely from LS parts.
The trigger and SDLC boards still seated in the cage, above the CPH 8100-60 ST backplane connectors.
The 01640-66510 SDLC board out of the cage, with an 8286A transceiver along the bottom edge.
The 01640-66512 trigger board, filled with 2102 static RAMs down the right-hand side.
The main CPU is an AM9080, a 8080 clone (1820-2006).
Initial startup
After cleaning the machine started but with an error message:
The format screen after cleaning, with WARNING--RAM ERROR, U-32 across the top.
U32 was a socketed chip with the HP number 1818-0348 which should be an AM9102DPC, a 1024x1 bit static RAM. Swapping the chip on other places where it is used follows the chip around so it is the chip..
