DG Nova repair etc.

Hi Bruce, thanks for taking your time to answer my mail! Sorry to leave out details, i know how frustrating it is if people forget the important bits of their problems ;) I have (at least sighted) all documentation from bitsavers: http://bitsavers.informatik.uni-stuttgart.de/pdf/dg/ and read a good amount of code and documentation of the simh project (because i would like to build a media emulator for this machine later....maybe) My main problem is that most of the stuff from bitsavers seems to be for newer machines that have a builtin ROM? My machine does not have the program load option (at least theres no switch for it) and i was under the impression that all documentation i found somehow just loaded a stored program for the check procedures. Am i wrong with this? So, in short i did not find any checkout procedure that looked adequate for my machine so i just hacked in some small asm programs that at least ran on the simulator. Actually, the machine runs simple nop jumps at least 1: jmp 2 2: jmp 3 3: jmp 1 If i remember right when running this program it did not even hang itself up (aka you could "stop" the machine). But i prepared the popular "Hello World" asm example to run without RDOS, and it obviously failed at least because of the stuck ACs. I mean, how can you write anything meaningful without using an AC? ;) By "Reset" i mean pushing the reset switch up when pressing down for "stop" does nothing. Again i may be subject to interpret the meaning of STOP and RESET wrong. Clearly this machine is confusing me ;) We will examine the power supply for sure! It bugs me that we did not think of that, since for now we only get to the machine once per week. We may also have the option to take it home though.... Also a friend of mine (which should be registering here soon, too - and is more experienced than me when it comes to electronics) said that the machine was acting strange when he first powered it up after it sat for a week (aka cold). Maybe that points to another aging/heat related/power supply problem. Thanks for clarifying the internal structure of the machine. I was not aware of that although i looked at alot bus pinouts, transfer timings, signal descriptions etc. See above, confusing! The third party board is unidentified for now. We tried to run without it but saw the same error. We also already noticed that the machine runs only with 2 CPU boards and nothing else, at least the PC counts and the ACs still deposit and load. I promise to take quality photos of anything you like once we get back to the machine. I apologize for the bad photos my phone makes. best regards Alex On 02/15/13 18:03, Bruce Ray wrote: