General Category > Lisa Troubleshooting and Repair
Widget servo twist
compu_85:
I'd say, as you adjust the pots, avoid leaving them at an extreme. If turning it one direction doesn't "improve" the situation, stop. Also note they do interact with each other.
-J
ried:
Understood. Okay to start with Tacho Offset, LED current, Tacho gain? Seems a lot easier than disassembling the board and adjusting A', B', B, A amplitude.
compu_85:
I think I left the LED one mostly alone. If you get a long, thin screwdriver, and remove the shield piece from the back of the motherboard, you can adjust them with everything hooked up.
stepleton:
--- Quote from: ried on February 05, 2023, 06:46:52 pm ---I need to look into this. Sounds like that is the next step. Is there a guide to tuning these? Better yet, what should I specifically avoid doing, if anything?
<...?
Edit: Found this very helpful post:
https://lisalist2.com/index.php/topic,15.msg37.html#msg37
However, working with an oscilloscope is beyond my hardware and skillset at this point. Hmmm...
--- End quote ---
I think the calibration method is described in the Widget ERS document on Bitsavers. This is basically the Bible of Widget, and (unfortunately) an oscilloscope with X-Y capability is required. Look for key waveforms near the back.
ried:
Well, this is not something I was expecting to do:
https://imgur.com/W6nsTCK
But adjusting B' slightly did result in this additional movement:
https://www.youtube.com/watch?v=g4196_uTkl8
Update: Nice to see the internal disk appear as a startup option:
https://imgur.com/a/zNYmuZB
Not working yet, of course. I suspect I don't have the knowledge or tools to fine-tune this enough to actually make it usable. But this is progress, it seems!
Update 2: The drive is seen by BLU 0.9 now, and responds to the Exercise / Test Disk function, for example. It goes through the physical motions of the exercise, and eventually generates an Error E803:
https://imgur.com/a/1AAhphs
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