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TRS-80 Model 4 - Power on with blank screen

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    TRS-80 Model 4 - Power on with blank screen

    Hello everyone

    Have TRS-80 Model 4 that powers on with blank screen. Floppy light red for few second on booting. CRT tube no heating or noise.

    What I did:

    Scrolling brightness/ contrast, not helping.
    Holding break key, not helping.
    CRT folk on place.

    Any suggestion?

    #2
    Is your Model 4 a Gate Array Model or Non Gate Array Model. (You can tell by the RS-232C
    Port. If the RS-232C port connector is sticking straight down (towards Desk) it's a Non Gate
    Array Motherboard. If the RS-232 Connector sticks towards the back of the Computer it is
    a Gate Array Version.)

    That should get us to the correct Video Board.


    Larry

    Comment


      #3
      so if you know "CRT tube no heating or noise." then I will assume you already opened the computer.

      disconnect the PSU (if a single one) and take it off the disk drive bracket, then reflow all the pins of the connector without forgetting the extra 2 that bring power to the video board, reassemble and power up and test 2 pin connector to see if power is leaving the psu for the video board, seethe technical manual below for where/how much should be coming out of pins.

      M4 NGA https://drive.google.com/file/d/1eZG...ew?usp=sharing
      M4 GA https://drive.google.com/file/d/1AzZ...ew?usp=sharing
      Texas Tandy Blog: https://texastandy.blogspot.com/, My Discord " Tandy and TRS-80 Owners" (https://discord.gg/VCDPG8j)
      Gaming: i7-8700K, 16GB, 1TB SSD, RTX 2060, Dual 27" LG IPS Monitors.
      Vintage: TRS-80 MODEL 4, 128K RAM, Internal: 360K FDD, Gotek USB FDD & FreHD HDD Combo, External: 360K & 720K FDD, RS232-WIFI MODEM, DWP-210

      Comment


        #4
        Originally posted by ldkraemer View Post
        Is your Model 4 a Gate Array Model or Non Gate Array Model. (You can tell by the RS-232C
        Port. If the RS-232C port connector is sticking straight down (towards Desk) it's a Non Gate
        Array Motherboard. If the RS-232 Connector sticks towards the back of the Computer it is
        a Gate Array Version.)

        That should get us to the correct Video Board.


        Larry
        Greetings Patrick

        As you mentioned, the problem was with PSU. Pins had dry soldering.

        Check picture.

        Problem with CRT solved.

        Thank you very much!
        20210410_194541.jpg

        Comment


          #5
          Originally posted by Patrick Bureau View Post
          so if you know "CRT tube no heating or noise." then I will assume you already opened the computer.

          disconnect the PSU (if a single one) and take it off the disk drive bracket, then reflow all the pins of the connector without forgetting the extra 2 that bring power to the video board, reassemble and power up and test 2 pin connector to see if power is leaving the psu for the video board, seethe technical manual below for where/how much should be coming out of pins.

          M4 NGA https://drive.google.com/file/d/1eZG...ew?usp=sharing
          M4 GA https://drive.google.com/file/d/1AzZ...ew?usp=sharing
          I sent reply, but not published yet.

          Hi Patrick

          As you mentioned, the problem was with connector pins in PSU.

          Attached a picture before reflow.

          Thank you 20210410_194541.jpg

          Comment


            #6
            Your welcome this is why we maintain this forum ) anytime here *I check it once a day, or on my discord channel (listed in my signature)
            Texas Tandy Blog: https://texastandy.blogspot.com/, My Discord " Tandy and TRS-80 Owners" (https://discord.gg/VCDPG8j)
            Gaming: i7-8700K, 16GB, 1TB SSD, RTX 2060, Dual 27" LG IPS Monitors.
            Vintage: TRS-80 MODEL 4, 128K RAM, Internal: 360K FDD, Gotek USB FDD & FreHD HDD Combo, External: 360K & 720K FDD, RS232-WIFI MODEM, DWP-210

            Comment

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