• Please review our updated Terms and Rules here

Search results

  1. W

    Restoring a DEC PDP-11/05

    Honestly given my experience with vintage computers, I wouldn’t have considered oxidation and corrosion on things to be an issue. I suppose when you take into account that there was at one point a mouse living inside, (I found a whole peanut in the power supply) the idea of corrosion seems more...
  2. W

    Restoring a DEC PDP-11/05

    I have continuity for both AC and DC LO the connector on the PSU all the way to the backplane. Looking back, I only had one of the M930’s plugged in to the backplane. Perhaps I’ll take another look and see if having both unibus slots makes a difference.
  3. W

    Restoring a DEC PDP-11/05

    Could this be the reason why nothing appears to be working? I found it odd that I’m getting measurements where the DC AC LO connect to the backplane and not on the power supply itself. Speaking of the backplane, I couldn’t help but notice there appears to be some non-factory wiring on some...
  4. W

    Restoring a DEC PDP-11/05

    Measuring right off the backplane, DC LO reads 3.5 volts. AC LO reads 4.11 volts. From the connector on the power supply, pins 3 and 6, BUS AC LO L reads 0.00 volts and BUS DC LO L reads 0.00 volts.
  5. W

    Restoring a DEC PDP-11/05

    Are you referring to the AC LO and DC LO that originate on the power supply? I don’t think I ever recall seeing anything high on either when I was working on it. I hope my memory serves me correct. I’ll start it up later on today and report back. I haven’t checked the new set of boards yet...
  6. W

    Restoring a DEC PDP-11/05

    The plot thickens(?): Through the generosity of another user, I was able to procure another M7260 and M7261. Here’s the peculiar bit- After swapping out the boards, I powered the system up and was greeted with the same blank front panel. I’ll admit, I had hopes of seeing at least something...
  7. W

    Restoring a DEC PDP-11/05

    I took a look at the PROM inputs on 102 and 112. High inputs all read high and low inputs all read low. Back to 102 and 112; Enable pin 13 is low and Enable pin 14 is high on both. I’ll take a look at the other PROMs tomorrow, as I’d like to double check everything before I break out the...
  8. W

    Restoring a DEC PDP-11/05

    Would failed PROMs also be the reason I can’t seem to single step anything with the M CLK switch?
  9. W

    Restoring a DEC PDP-11/05

    Here are the read outs I took today with the DMM: (from sheet CONE) E108: 1- 3.30 2- 3.30 3- 3.30 4- 3.30 5- 3.30 6- 3.45 7- 3.45 9- 3.30 10- 3.84 11- 3.54 12- 0.26 13- 0.24 14- 0.24 15- 3.90 E109 isn’t referenced on CONE. Did you mean E107? The way they wrote the seven looked like a nine...
  10. W

    Restoring a DEC PDP-11/05

    By “other PROM(s)” are you referring to E102 and E112- the next instruction high and low bits? And if so, what inputs/outputs should I be looking for that indicate the PROM is enabled?
  11. W

    Restoring a DEC PDP-11/05

    Is that CONF? I’ll take a look today. I don’t think the screenshot posted. Edit: Going off of drawing CONF, for E101 pin 12 (MPC06) is at 0.33 volts. Pins 5,4,13 (MPC 07, 05, 04) read 3.30 volts For E111, the MPC 0,1,2,3 inputs read 3.30 volts Using the KM, holding down the M Clk switch...
  12. W

    Restoring a DEC PDP-11/05

    I’ll take a look at those. Do you know which prints would be the most useful?
  13. W

    Restoring a DEC PDP-11/05

    Do you think it could be an issue with the ROM that’s giving invalid MPCs? Just to rule it out, I also checked every LED on my KM-11. (I had replaced two that were dead and one that was always dim to avoid confusion in the future)
  14. W

    Restoring a DEC PDP-11/05

    I tried again, this time with clock set to manual before turning the system on. MPC 00-05,07 are lit and MPC 06 is dim. When reading the micro codes from the KM-11 do you read them from lamps 00-07 or 07-00? They would be in octal too, correct?
  15. W

    Restoring a DEC PDP-11/05

    Alright then. The KM 11 is plugged into the designated slot in the row closest to the front of the machine. I started it up and followed the manual on using the KM11 with the KM 1 overlay. Depressed the halt switch and held down the start switch. Toggled the m clock twice. Released the start...
  16. W

    Restoring a DEC PDP-11/05

    Bit of a stupid question; The manual says to plug the KM-11 into position A2. If I’m reading the backplane layout correctly, the M7260 module is in slot 2, rows A-F, and there is nowhere to plug in the KM-11. Is this correct? The label on the chassis lists KM-11 in slot 1, along with M9970 and...
  17. W

    Restoring a DEC PDP-11/05

    Hello everyone- It’s been a little while but now I have assembled a KM-11 maintenance module from Guy at Shireshoft. (Excuse the large toggle switch- there weren’t any spdt momentary mini toggles in stock so I had to use a dpdt) I’m going to do a little reading on how to use the KM-11 to...
  18. W

    Restoring a DEC PDP-11/05

    Just to clarify, are connections to the backplane represented by a two-letter designation followed by a 1 or a 2? For pinouts of the NXT field, do you know which schematic I should be looking at?
  19. W

    Restoring a DEC PDP-11/05

    I guess I’ll look into building a KM11. Compared to running test leads from the ic pins to the logic analyzer inputs, it seems a lot simpler. Just out of curiosity, how would I trigger a DC or AC low?
  20. W

    Restoring a DEC PDP-11/05

    E101 and E111 are both receiving a clock signal on pin 9. To save having to upload numerous screen captures showing a ~4 volt signal, I'm just going to list the IC's and whether their input/output was a high or low. Logic high for me seems to be between 3.75 and 4.00 volts according to my...
Back
Top