PDP-11/10 repair started

tony duell ard at p850ug1.demon.co.uk
Sun Oct 4 14:52:21 CDT 2015

> the microcode is "on the menu" for next weekend ...
> The system is a 11/10S, CPU is M7260 and M7261.

Are you sure that's an 'S'? I thought the 'S' was the M8260/M8261 board
set with the links to disable the bus arbiter so it can be used as a slave

Anyway, getting back to this... I had forgotten that the 11/10 loads the LED
data serially into a shift register on the console board. Is that clock and counter
running (on the console board)? Also check round the '150 mux on the data path
board, that is the source of the bitstream for the LEDs

The switch logic seems to be sheet CONE in my printset (which is actually for
the GT40, but it's the same processor). On the control logic board, ROM
E100 seems to determine the microcode address for console operations.

Start with CONE BUT SWITCHES L, which seems to be an overall enable for this. 
It starts from the '154 E078 on that board (sheet CONE again). It is controlled by
the microcode ROM E105 (sheet CONG). Microcode program counter is E102
and E091 (sheet CONF). Also look at the CPU clock (sheet CONJ). Is it running? If
not, look at those gates E013d, etc, that disable it. 

That's something to be going one with anyway...


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