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had to take a break on this one, but I did isolate the offending chip and have it able to boot now! It was a 367. I burned the diagnostic rom and am making progress but I may still have a couple of bad ram chips. I have another non-working model 1 that I plan to torture myself with soon...

I have had a Bally with similar symptoms (no +5v, no video) that I've been farting around with for a couple of years. I finally sent it off to Allen S. in Kansas who owns a Balcheck diagnostic device. He identified the bad RAM chip within 20 minutes of receiving it and had it scribbling...

this crusty, rusty model 1 has the 3 chip rom board. I'll dig out my romulator z-80 and programmer today. there's a model 1 diagnostic rom on GitHub, or what roms would you recommend loading?

thanks, Larry. on the clock signal Z59-6, it looks odd. z40-6 and z59-14 pics below with all chips in. with Z40 and z59 out, voltages are: z40-20 1.5 z40-22 1.5 z23-2 1.5 z23-1 1.5 z22-2 4.5 z22-3 4.0 z25-9 4.0 z25-10 0.2 z25-8 4.5

thank you! Z-43-1 is low all the time.

sorry, got sidetracked with work stuff. z40-14,15,12,8,7,9,10,13 = 2.5v z76-11,13 = 4.2 z75-5,7,3,9,11 = 4.2 z68-9,3,5,7 = 4.2 z68-10,2,4,6 = 0.5 z67-9,3,5,7 = 4.5 z67-10,2,4,6 = 0.5 z44-7,5,3,9 = 4.5 z44-6,4,2,10 = 1.5 z60-9,7,5,3= 4.2 z60-10,6,4,2= 1.5

Z76-1 4.6v Z75-15 0.2 Z60-1 3.9

the 74175 Z59 seemed bad. 2nd picture is with Z3 removed, @9 as expected? 3rd picture is Z3 in, all on, 1@A@ repeating. progress, I guess. and what is the function of the board in picture 1?

thank you! Z41-1 is solid low. I'll look through the info above. thank you again!!

Thank you (again), Larry! Hope you're doing well this new year! I had reviewed the diagnosis doc you referenced, and tried removing Z3 with the same results. a screen full of @.

This junk machine has worked recently, but now only boots to a full screen of @ symbols. The only previous problems I had in getting it running had to do with vertical sync, but I had that working, displaying the level 2 basic screen and seemingly working. now just @. Any pointers on what...

panel on, still works! only lost one nylon spacer during the repair, printing some now.

found it! a tiny solder blob on one of the switches to the trace next to it. I'm able to run test 1 now! sorry for wasting your time today, but I always learn from these troubleshooting threads. thank you so very much!!!! I have some serial cards and a video card I want to explore soon...

I have not reversed the connector. figured it out early on and the orientation is pretty clear in that the ribbon comes out of the top side of the CPU with red to the right. when I had the machine functioning it was in this position also. with 4 and 12 up/open/on does not change anything...

LD4 stays out after power, stop, reset with CP-A and CPU in. I went through and retested the 7405 stuff just now in this state. C3, LAD, HAD, NOP all LOW. U2 socket 4/13 LOW, all others HIGH. 7405 in/out are all low/high EXCEPT: U6-10 = L U3-8 = L U7-10 = L U3-6 = L this useful? let me...

yes, of course, and happy new year!

Well, it was great while it worked!! I left it alone, then did some slight cleanup and reassembled the front panel and now I have a similar but different problem. panel and CPU in, power, stop, reset. LD4 LED is off and all other data LEDS are on. going through the steps from the previous...

Any other things you'd suggest trying at this point? I need to do some cleanup. Seems to be working for tests 1 and 2. back connection on old sockets seems to have been the primary problem. test program 2.

Test program 1 appears to be working!! the left switches toggle the corresponding data LEDs! I'll go through the other test and report back. thank you so much!

post 63 tests: all data LEDs are off. all U2 pins are low. data leds 0, 1, 6, 7 are on but I'm a little confused by the "should activate the C3 signal" part. U10-12 x no signal (U10 is removed) U6-5 x, U6-6 low U6-3 x, U6-4 low U6-11 x, U6-10 low U6-9 x, U6-8 low is this the expected...