LisaList2

Hey, that's awesome! Congrats!

Not sure if you know, but a rarely-used (or at least it seems rarely-used to me because very few people mention it) feature of ESProFile is its diagnostic mode, which might be pretty helpful in getting your Widget running. I spent far more time developing the diag mode than I did the emulation mode, so it's pretty full-featured, and supports nearly every command in the Widget's rather large command set other than the block read and block write commands. So you might be able to use your ESProFile not only as an emulator, but also as an aid to get your Widget running again!

Congratulations! Welcome to the party 

More good news! I dug out a crystal in my parts bins and did a swap and the Lisa came to life and passed all its test besides the widget drive which is expected. I may start a new thread troubleshooting that. I will install the proper crystal when the part arrives tomorrow but really happy with this progress. Now to recap the power supply and wait for my ESProfile board to come in for a boot drive! I'll update once we I have Lisa OS booting but I think we are looking good. Again appreciate all the help here it has been indispensable for this more advanced repair for a beginner!

The transistors looked ok but the Hfe values on my tester were very low on Q1 compared to the Q2. Since I had some that would work I replaced the Q1 & Q2 transistors and had no change in my probe measurements or behavior of the machine. I also confirmed 12v+ at the R4 resistor, Im not sure I have a crystal on hand, but going to look and I ordered a new 16Mhz one which will be here in a couple days.

QuoteThanks for the tip, I probed U68-LS132 Pin 3 and see basically the same thing.

Sounds like you've narrowed it down a lot!

Suggestions:

Check for physical damage to the transistors as they can be bent/broken by rough handling.

Check for +12V at R4.

Swap in another crystal (even a different frequency) to see if the rest of the oscillator circuit works.

Thanks for the tip, I probed U68-LS132 Pin 3 and see basically the same thing. I lowered the voltage to 1.0/div for more detail but basically a flat line as before.

QuoteGreat suggestion. I think I may have found the issue. The 16Mhz FDC clock Y1 appears to be dead if im reading my scope correctly. Compared to the others there is zero activity.

If you are probing the portion of the circuit connected to the crystal itself, its behaviour may be altered/stopped by the loading of the scope probe. Double-check the signal after it is buffered, eg. at U6A-3

Great suggestion. I think I may have found the issue. The 16Mhz FDC clock Y1 appears to be dead if im reading my scope correctly. Compared to the others there is zero activity.

Yeah, soldering a wire and probing it is probably your best bet unless you have right-angle risers that let you probe the CPU board directly.

But given your symptoms, I'd be willing to bet that the problem is on the I/O board and not the CPU board. If something were wrong with the 556 that was causing it to assert BERR too quickly (or constantly), the Lisa almost certainly wouldn't be making it this far through diagnostics. So I'd suggest looking at the floppy controller on the I/O board instead, which is luckily a lot easier to probe!

Page 4 of the I/O board schematics should show you everything you need to see when troubleshooting the FDC. I've seen this exact same problem several times (including on my FPGA-based Lisa) and it's always been because of DTACK never getting asserted by the floppy disk controller at the end of the 68K read/write cycle. This could be caused by a variety of different things, from the 16MHz FDC clock being completely dead to a bad 8T97 that buffers the FDC's DTACK onto the main systemwide DTACK line, but something in there is likely to be your issue.

Hi all, any suggestions on probing while the I/O board is installed? I thought about soldering a wire to the pin and testing outside the machine. I also found it suggested that the Keyboard and Parallel port 6522 interface chips could be bad, as a test I swapped them with no behavior change, and also removed them both completely which caused error 50 to briefly show but then the image was distorted and did not redraw.