LGP-30 Video Update

william degnan billdegnan at gmail.com
Sat Feb 25 20:38:23 CST 2017

On Feb 25, 2017 9:24 PM, "Cory Heisterkamp" <coryheisterkamp at gmail.com>
> Some promising news on getting the LGP-30 up and running. With all
systems stable, I tightened the head spacing on the three timing track
heads (using brass 0.001" feeler gauges though I may have to go closer).
This has resolved 'hanging' when hitting Start; it actually appears to
execute for a cycle before toggling back to Stop for each press of the
Start key. Of course without being able to see what's happening, it's
likely just 'executing' garbage, but it's a solid first step.
> In Manual mode, keystrokes from the Flexowriter now trigger a
Stop/Compute toggle for each key entered and status neons on the flip-flop
cards are registering unique bit patterns as each comes in.
> I put the scope on the (rebuilt) clock generator card and we have good
'T' and 'T-bar' signals propagating, but still haven't licked the 'digital
display' issue. After further probing, the display began to stabilize and
the single line expanded into the proper 3 for Counter, Instruction and
Accumulator, and eventually a bit pattern emerged for the Instruction. No
signs of data yet for Counter nor Accumulator, and there is an extremely
pronounced 'throbbing' and visible refreshing. Here's a video:
> System timing looks spot on (top trace), but I also see some 'throbbing'
when putting my scope on any of the three timing heads which seems a little
strange to me (example on lower trace). Here's a quick vid:
> One thought is that the timing and short register heads are still too far
off the drum surface for a solid signal, purely conjecture at this stage. -C

Great news,,,bring it to life.

Bill Degnan
twitter: billdeg

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