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  • m_thompson's Avatar
    Today, 03:53 AM
    Can you get a better image of the board side of the systems so we can see the part numbers on the handles, and a picture of the spare boards that...
    7 replies | 187 view(s)
  • jackrubin's Avatar
    March 20th, 2017, 01:25 PM
    Yeah - I have days like that too.
    10 replies | 390 view(s)
  • m_thompson's Avatar
    March 20th, 2017, 03:38 AM
    m_thompson replied to a thread H724 woes, go figure! in DEC
    I always start by reforming the caps. The +15V output feeds the A1 regulator board, so a shorted C14, VR5, or Q10 could load the +15V. You...
    7 replies | 198 view(s)
  • jackrubin's Avatar
    March 19th, 2017, 04:04 PM
    jackrubin replied to a thread RK11-C / RK05 restore in DEC
    I've seen rub marks on the inner surface of several RK05 bottom covers, and also spacer pads to keep the sheet metal from deflecting upwards and...
    28 replies | 1191 view(s)
  • m_thompson's Avatar
    March 19th, 2017, 01:31 PM
    m_thompson replied to a thread RK11-C / RK05 restore in DEC
    My bottom covers are not installed yet. There is a warn spot on the front cover under the spindle, so maybe yours is not a unique problem.
    28 replies | 1191 view(s)
  • m_thompson's Avatar
    March 19th, 2017, 08:03 AM
    m_thompson replied to a thread H724 woes, go figure! in DEC
    I had the +5 regulator on my 8/e die. The LM723 on the A1 board was the problem. I soldered lots of wires onto the A1 board so I could see the...
    7 replies | 198 view(s)
  • m_thompson's Avatar
    March 11th, 2017, 10:35 PM
    m_thompson replied to a thread RK11-C / RK05 restore in DEC
    I had a bad 723 regulator on my 8/e, so that might be a possibility on the -15 regulator. I believe that the +15 and -15 regulators are the same...
    28 replies | 1191 view(s)
  • jackrubin's Avatar
    March 9th, 2017, 10:12 AM
    The Term-Mite ST-1000 was designed by Steve Ciarcia and featured in his Circuit Cellar column in 1984. The two-part article is reprinted in Volume 5...
    4 replies | 430 view(s)
  • m_thompson's Avatar
    March 6th, 2017, 09:04 PM
    My notes on that system are: Purchased in 1968/1969 time frame for use with EIA-680 Analog Computer for hybrid computation pair. The facility was...
    3 replies | 196 view(s)
  • MattisLind's Avatar
    March 6th, 2017, 08:49 AM
    Apparently the interface module is called M7452. It seems like the machine is somewhat intelligent in that it has both a 68000 and a 2901 bit slice...
    12 replies | 423 view(s)
  • MattisLind's Avatar
    March 6th, 2017, 07:59 AM
    This definitely sounds like interesting things. But I am in the wrong part of the world and should not get more stuff anyway. But I am a little bit...
    12 replies | 423 view(s)
  • m_thompson's Avatar
    March 5th, 2017, 06:28 AM
    m_thompson replied to a thread RK11-C / RK05 restore in DEC
    I would say no. If you put the toggle-switch on the servo-amp board in the down position it will disable the servo. If you put something soft between...
    28 replies | 1191 view(s)
  • m_thompson's Avatar
    March 4th, 2017, 05:30 AM
    m_thompson replied to a thread PDP-8/e Project in DEC
    On our 8/L all of the steering diodes had reasonable forward and reverse voltages, but we still had a section that did not work. We put 200mA through...
    70 replies | 3918 view(s)
  • m_thompson's Avatar
    March 4th, 2017, 04:14 AM
    m_thompson replied to a thread PDP-8/e Project in DEC
    I have seen lots of steering diodes fail in 8/I and 8/L core stacks. Maybe that is what is wrong with your stacks.
    70 replies | 3918 view(s)
  • m_thompson's Avatar
    March 4th, 2017, 04:13 AM
    m_thompson replied to a thread PDP-8/e Project in DEC
    There are some toggle-in serial tests that will check the skip, send, and receive logic.
    70 replies | 3918 view(s)
  • m_thompson's Avatar
    March 2nd, 2017, 03:43 AM
    m_thompson replied to a thread PiDP-8/I in DEC
    Lou, I have access to a running PDP-12, let me know if you need some help debugging VR12 behavior.
    125 replies | 13212 view(s)
  • m_thompson's Avatar
    March 1st, 2017, 08:27 AM
    m_thompson replied to a thread PDP-8/e Project in DEC
    Nope, just the earlier vanilla SN7474 parts. I haven't fixed anything new enough to have S or H parts yet.
    70 replies | 3918 view(s)
  • m_thompson's Avatar
    March 1st, 2017, 03:50 AM
    m_thompson replied to a thread PDP-8/e Project in DEC
    I have replaced an amazing amount of 7474 ICs in DEC equipment. I would replace it.
    70 replies | 3918 view(s)
  • jackrubin's Avatar
    February 28th, 2017, 04:46 PM
    jackrubin replied to a thread PDP-8/e Project in DEC
    I'm looking forward to your post, but 1488/1489 drivers were always notorious points of failure on serial lines. Not because they are bad chips but...
    70 replies | 3918 view(s)
  • m_thompson's Avatar
    February 27th, 2017, 08:15 AM
    Several months ago I cleaned and lubricated the brake bushings on my drive. Both drives on the PDP-12 and both drives on my PDP-8/e have the...
    219 replies | 22809 view(s)
  • m_thompson's Avatar
    February 27th, 2017, 03:48 AM
    m_thompson replied to a thread PDP-8/S on eBay in DEC
    The RICM has four PDP-8/S systems. We had the first one, a rack mount, running quite a while ago. It was amazingly slow compared to an 8/L or 8/I. ...
    3 replies | 260 view(s)
  • m_thompson's Avatar
    February 26th, 2017, 07:45 AM
    m_thompson started a thread PDP-8/S on eBay in DEC
    There is a PDP-8/S on eBay. Now is your opportunity to own the slowest PDP-8 ever built. It is also the lowest serial number 8/S that I know of. ...
    3 replies | 260 view(s)
  • m_thompson's Avatar
    February 26th, 2017, 07:40 AM
    The TC12 controller passed all diagnostics, but we didn't try the tape data test. During a tape format it writes the Timing and Mark tracks on the...
    219 replies | 22809 view(s)
  • m_thompson's Avatar
    February 26th, 2017, 07:15 AM
    DEC issued different versions of the documents. One of the front pages shows the date of printing. If your's are different than any on BitSavers, it...
    3 replies | 168 view(s)
  • m_thompson's Avatar
    February 26th, 2017, 05:20 AM
    Will you scan them and send them to Al?
    3 replies | 168 view(s)
  • m_thompson's Avatar
    February 23rd, 2017, 04:28 AM
    m_thompson replied to a thread RK11-C / RK05 restore in DEC
    Be careful with the elbow. Some get dried out and crumble. You have a later revision of drive if you have the elbow. I believe that the HEPA...
    28 replies | 1191 view(s)
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About m_thompson

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About m_thompson
Biography:
Volunteer at the RICM. Working on a PDP-8/I, 8/L, 8/E, PDP-9, 11/34a, and 11/44.
Location:
Rhode Island
Interests:
Vintage minicomputers.
Occupation:
Engineer

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Member of the Rhode Island Computer Museum
http://www.ricomputermuseum.org

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