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35898I'm in a good mood.. PT Helios II back up and running

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  • corey986
    May 10, 2014
      I was debating yesterday heading over to Infoage to work on the March Scelbi. I'm currently up to socketing the CPU board. I want to have power up for the June workshop session.

      But for some reason I decided, maybe I'll just lock myself in my basement and try to figure out what is wrong with my Helios and why it won't boot to PTDOS on either of my Sol-20.

      So last week I found a bad socket on the sol-20 Video on the unit currently hooked up to the Helios. It is the same stupid TI socket type as the Apple-1, but in this case this machine had a video upgrade when I got it that has a daughter board into this IC socket, so it must have weakened the contacts. Not really a Helios problem, but typical of these older machines, your always fixing something.

      So I also tracked down last week a bad ram chip on my 32kra that just doesn't work consistently when the board heats up. That one drove me a little nuts till I realized it was heat related which is why I got strange results depending on how long I ran the memory test.

      Also last week, on advise from a friend, I bypassed my front panel on the Helios with a special cable I made. Cost me almost $50 to make, which sucks but I won't be using two blocks of wood to put on IDC connectors and dip connectors anymore on ribbon cable. I have a special tool and I don't know how I lived without it before.

      So the second to final piece of this story is that I only had DISKT, the Helios troubleshooting program on disk. That wouldn't help me and no where on the internet could I find an ENT, Hex or audio file version. I couldn't even find an ASM file version. All I could find was a PTDOS program image. So a couple of weeks ago on one of my work trips sitting on a plane I wrote a program to convert PTDOS images to ENT files that can be loaded into Solos. While I was at it I also wrote one that could do intel hex to ENT. Both are on the retro-restore yahoo group.

      So armed with DISKT, an Oscilloscope and the Helios service manual, I tracked down my problems to a chip on the formatter. Sure a chip that is oddball so I couldn't test it using my IC tester. So I borrowed one from my spare formatter card (one that has had no factory mods, which is why I won't use that one, it's temperamental) and Huzzah!!!! I'm booting PTDOS.

      So I'm in a very good mood this morning... Anyway off to Kickboxing and the 3 Lacrosse games in the mud.

      Maybe Monday I can get some work done on that MARCH Scelbi CPU card, before my week gets crazy.

      Cheers, Corey