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Thread: Atex PDP-11/34

  1. #21
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    Quote Originally Posted by Nick7928 View Post
    Hey everyone, while I was waiting for an oscillocsope, I decided to check all the voltages again to make sure that they were in spec, and while checking the -15 and +15 volt line, it showed 30 volts. Is this normal?
    Measured with respect to what reference? System GND? If you measure from -15V (on meter v-) to +15V (on meter v+) yes that would read +30V difference.

    OTOH if -15V to GND reads -30V and +15V to GND reads +30V then that is a problem.

  2. #22
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    Quote Originally Posted by Nick7928 View Post
    Hey everyone, while I was waiting for an oscillocsope, I decided to check all the voltages again to make sure that they were in spec, and while checking the -15 and +15 volt line, it showed 30 volts. Is this normal?
    Did you measure across the -15 V and +15 V lines? If so, then 30 V would be correct since there would be a 30 V potential across both. You need to measure each one individually against ground to see what they are.

  3. #23

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    Ah yes, I had completely forgot about that, I checked all the voltages and they seem in spec. What initially worried me was that the lamp on the H745 PSU went out, but it was an old incandescent light bulb which I will replace with an LED.

  4. #24
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    Quote Originally Posted by Nick7928 View Post
    No the system was in pieces when I had gotten it and I am referring to the ebay listing and common sense to get me through
    Make sure you save the pictures off the ebay listing as ebay will delete them some time after the auction is closed.

  5. #25

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    Hello everyone, it has been a few days since I had borrowed a 50MHz oscilloscope from my friend, and when I put it to the send line on the pdp 11 serial card, I get garbage on the oscilloscope. I may think that this is a problem with the power supply being too loud, but at the same time, I may be seeing something, but it might be going through way too fast for me.

    Thanks everyone!

  6. #26

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    Hello everyone, I was on a vacation for some time and as a result, didnt have time to post. I went to the living computer museum in Seattle and talked with someone who has a general knowledge of Atex machines. Also I had gotten the cables that I need to connect up the Workstation III lan card to the small board. When I power up the computer, the LEDs on the lan board only show that 5 volts is being sent to the card but not 12. Is there any way to test that there is 12 volts going to the card?

    Photo of the board: https://imgur.com/a/ahUvWbF

  7. #27

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    I had fixed the problem with the card not getting 12 volts, It turned out that the backplane was not giving it 12 volts so I had connected it to a different one and it now shows that 5 and 12 volts are present. When I load TeraTerm on my laptop, turn on local echo, and connect it to the serial port of the Workstation III card, the receive LED blinks when I type random characters into the terminal, but the transmit light stays off.

    Is there any way to determine that the CPU board is talking with the Workstation III card? Or that the CPU works in general?

  8. #28
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    Quote Originally Posted by Nick7928 View Post
    Is there any way to determine that the CPU board is talking with the Workstation III card? Or that the CPU works in general?
    You need to concentrate on identifying which serial port is the ODT console port that the J-11 CPU will talk to if it is configured to enter ODT at reset. This port is also commonly used by the DEC and Unix OSes as the system console port. No idea if that is what the Atex stuff will use. If you can do that, then you have a way to evaluate if the CPU board is functioning and could download various tests via the ODT prompt to start to exercise the rest of the system, if you can identify what the peripherals are.

  9. #29

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    Ok! Thanks for the advice!

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