PDP-11/10 repair started

-----Oorspronkelijk bericht----- From: tony duell Sent: Sunday, October 04, 2015 8:16 PM To: General Discussion: On-Topic and Off-Topic Posts Subject: RE: PDP-11/10 repair started It's been a long time since I've been inside an 11/10 (that will change soon as I fix the one damaged by the idiot removal men,..) but just to eliminate the obvious check that ACLO and DCLO are solidly high. On a system like this I would always start by looking at the microcode program counter. What state(s) is it in? If it is sequencing through states, does the sequence make any sense? Does anything happen when you press LOAD ADDR (say)? Maybe start from one of the switches like LOAD ADDR and see if it is generating the right signals on the processor board. -tony ========= Oops, I forgot to mention a few other checks that I did ... AC LO and DC LO are some 4.6V. Both have a 130 mV ripple, no spikes. That seems OK to me. As the console ribbon cable was disconnected, I also checked the toggle switches (LOAD ADDR, EXAM, START, CONT, DEP) and the switches SW0~SW15 and HALT/EANBLE. In the OFF position the signal is 0.06V and in the ON position I measured voltages between 4.5 and 4.6V. Toggles and switch signals seems OK too. I am fairly confident that the console itself is OK. Thanks for the tip checking the microcode program counter. I hope to get to that next weekend. Also, with the correct module on extenders I will check what toggling LOAD ADDRS does signal-wise. Looking at the console LEDs it does nothing :-/ thanks, - Henk