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  • DougIngraham's Avatar
    Yesterday, 05:54 PM
    Hey Vince. If you use a 74HCT238 you don't need to invert the outputs thus avoiding the sacrilege of using a 3 input nand as an inverter.
    70 replies | 3222 view(s)
  • DougIngraham's Avatar
    Yesterday, 05:13 AM
    I may have found another crappy scan. http://www.vandermark.ch/pdp8/uploads/Hardware/Hardware.PC8E/pc8e.pdf I didn't see anything specifying what...
    70 replies | 3222 view(s)
  • DougIngraham's Avatar
    September 17th, 2020, 02:53 PM
    BV2 is Power Ok on the Omnibus I think. What did they connect it to since that wasn't what they wanted? I see now. The 7438 is what Roland was...
    70 replies | 3222 view(s)
  • DougIngraham's Avatar
    September 17th, 2020, 10:04 AM
    I have the M840K revision also. And that cap is C65 on the diagram which goes across the 4 diodes in series. It is definitely installed backwards....
    70 replies | 3222 view(s)
  • DougIngraham's Avatar
    September 17th, 2020, 09:23 AM
    My missing chip is E33 (DEC 8881) which is the Omnibus buffer for the upper 4 bits of the reader port. Have to find a 7438 to replace it with. I...
    70 replies | 3222 view(s)
  • DougIngraham's Avatar
    September 17th, 2020, 08:07 AM
    I located my M840 and the cap appears to be installed + to + as Vince indicates his is. I ohmed the + side of the cap does appear to go to the...
    70 replies | 3222 view(s)
  • DougIngraham's Avatar
    September 14th, 2020, 08:59 PM
    DougIngraham replied to a thread Decmate II question in DEC
    I am pretty sure all three variants of the Rainbow have a Z-80 and could run CPM. The Z-80 is the processor that talks to the floppy drive on the...
    11 replies | 345 view(s)
  • DougIngraham's Avatar
    September 14th, 2020, 02:47 PM
    DougIngraham replied to a thread Decmate II question in DEC
    I pulled an old DOS machine out of the closet that had a 3.5 inch drive. I located a 1.2 mb 5.25 inch floppy drive and installed it in the machine. ...
    11 replies | 345 view(s)
  • DougIngraham's Avatar
    September 14th, 2020, 06:14 AM
    DougIngraham replied to a thread Decmate II question in DEC
    It seems like your biggest problem is the number of unknowns. You eliminated two of those by removing the hard disk and replacing the floppy drive...
    11 replies | 345 view(s)
  • DougIngraham's Avatar
    September 11th, 2020, 08:16 PM
    DougIngraham replied to a thread Decmate II question in DEC
    I've only had a couple of hours of time playing with one and that was a few weeks ago. The hard disk is ignored if it can't read or if the first 4...
    11 replies | 345 view(s)
  • DougIngraham's Avatar
    September 10th, 2020, 06:29 PM
    DougIngraham replied to a thread Fixing a RX02 drive in DEC
    Hi Roland. You directed me here and I feel compelled to add something. You need to find an 8" alignment disk. I have a Dysan one but I can't...
    15 replies | 1145 view(s)
  • DougIngraham's Avatar
    September 10th, 2020, 12:35 PM
    I have an M840 which Warren had collected along with a reader/punch. The reader punch is not in the best condition if I remember correctly. It...
    70 replies | 3222 view(s)
  • DougIngraham's Avatar
    September 9th, 2020, 08:08 PM
    As mentioned previously, I spent the day with vrs42 aka Vince. When I arrived the agenda had changed and the idea was to see if we could get a TU56...
    70 replies | 3222 view(s)
  • DougIngraham's Avatar
    September 8th, 2020, 01:02 PM
    I worked some more on the paper I am writing about implementing CALL/RETURN with a stack on the PDP-8. This is part one of two or three with the...
    70 replies | 3222 view(s)
  • DougIngraham's Avatar
    September 8th, 2020, 12:34 PM
    The problem with a find like this is that the only real value it has is what someone is willing to pay for it. In the mid 80's when I bought my...
    30 replies | 2446 view(s)
  • DougIngraham's Avatar
    September 2nd, 2020, 05:41 PM
    I am most interested in DECtapes that are original DEC software distribution tapes. I have several hundred reels of DECtape but the original...
    30 replies | 2446 view(s)
  • DougIngraham's Avatar
    August 27th, 2020, 10:41 AM
    PLA takes paint well and the COSplay people use it because it is great for making costumes. Auto body filler adheres well. One downside of PLA...
    35 replies | 1526 view(s)
  • DougIngraham's Avatar
    August 27th, 2020, 10:11 AM
    I am visiting Vince Slyngstad and we repaired his prototype omnibus spacewars board. This of course would need some explanation of why it was...
    70 replies | 3222 view(s)
  • DougIngraham's Avatar
    August 26th, 2020, 07:13 AM
    I am not sure I want to be in any kind of business again. However, once you get it worked out, 3D printing handles in reasonably low volumes would...
    35 replies | 1526 view(s)
  • DougIngraham's Avatar
    August 25th, 2020, 08:11 PM
    That mold line looks worse than on the 8/e's I have seen. Perhaps the molds were wearing out. About modeling in the mold lines, you are funny.......
    35 replies | 1526 view(s)
  • DougIngraham's Avatar
    August 23rd, 2020, 07:42 AM
    In my experience the switch failures are not due to age. They come about because someone thinks they can carry the 8/e chassis by themselves. You...
    35 replies | 1526 view(s)
  • DougIngraham's Avatar
    August 21st, 2020, 07:46 AM
    I've never liked using literals. They always seemed to cause more problems down the line when your code runs into the literals at the end of the...
    38 replies | 3744 view(s)
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About DougIngraham

Basic Information

About DougIngraham
Biography:
Retired now. Worked with computers since 1973.
Location:
Rapid City, SD USA
Interests:
PDP-8's, SOL-20. Photography, Electronics, 3D modeling and printing, Space stuff, EV conversions.
Occupation:
Retired, Network Analyst, Consultant, Programmer, Mainframe maintainer, TV Broadcast Engineer

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Doug Ingraham
2nd owner of Straight 8 SN1173
5 other PDP-8's including an 8/i and a DECSet 8000
SOL-20

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