Adapting a 19" color Apollo monitor for use on a PC

Here is information contributed by my brother Mark on how to adapt a Apollo 19" 1024x800 color monitor for use on a PC.

DISCLAIMER: The circuit presented here has destroyed video cards during testing. Use at your own risk!

OVERVIEW

This circuit allows a PC to display video on an Apollo 19" color monitor, P/N 008398-001. These monitors are fixed frequency, 1024x800, 60 Hz vertical refresh, sync-on-green. Horizontal and Vertical sync are active low. Many PC video cards will support 1024x768 resolution, which is generally close enough that the monitor can sync to the video signal produced. The number of colors supported by the video card is unimportant as the monitor is analog and will support 16/256/16K or greater colors.

This circuit has not been tried on the higher resolution 1280x1024 Apollo monitors which have a different horizontal and vertical scan frequency.

ADVANTAGES

  • inexpensive, ~ $10 in parts
  • passive components, no power source needed
  • known to work with a Diamond SS24X video card, ISA, 1MB under Windows 3.1, 3.11, Windows 95, and Linux.
  • known to work with an Expert Color DSV3365E video card, 2MB, under Windows 3.11 and Windows 95. This video card uses the S3 Trio64V+ graphics chip and seems to have a lot of ringing on the sync transitions which helps the monitor to sync up very niceley.

    DISADVANTAGES

  • The monitor will not sync up to anything other than roughly 1024x768 so there will be no display during bootup in VGA mode (640x480) an no playing of games which require other than 1024x768 resolution.
  • You still need a VGA or multi-sync monitor during initial setup and testing.
  • You might DESTROY YOUR VIDEO CARD!!!. The circuit has already destroyed a Trident 8900/8001 video card.
  • You might never get this to work for ATI brand video cards as their horizontal and vertical syncs seem to always be in opposition and might not allow for the necessary negative sync on both signals.

    CIRCUIT DESCRIPTON

    The circuit results in an "wired-OR" of the Horizontal and Vertical sync signals to produce a composite sync signal. Not all video cards can handle this. Then a trim-pot is used as a resistor divider to tap off 0.5 volts of composite sync needed by the monitor. The composite sync signal is then summed with the green video signal.

    A SAMPLE ADAPTOR

    One method of construction is seen below. It involves taking a PC slot cover blank and mounting three female BNC connectors to it. A short cable connects to the video card of the PC and passes the signals back to the BNC's mounted on the bracket. The video is supplied to the monitor on three equal lengths of 75 ohm coax with BNC connectors on each end. Note: Keep video cable coax lengths identical and less than 4 feet long.

    Another method would be to build a cable bundle with 3 BNC connectors on one end and a 15 pin male VGA connector at the other end. The passive components would be bundled inside the cable itself.

    Pin reference looking into the pins of a standard 15 pin VGA connector.

    SAMPLE PARTS LIST

    Here's a sample screen shot as captured by a Wincast PCI TV-Tuner card off the 19" Apollo color monitor driven by Windows 95.

    If you point the camera source at the monitor which is displaying the camera output you get this "infinity" look.

    SETUP and TESTING

    You must have a monitor cable of displaying VGA resolution to boot up your system until everything is setup and working properly. Afterwards you should no longer need the VGA monitor.

    With the VGA monitor attached and the cover off of your machine, setup your windows or linux video to:

  • a video mode of 1024x768, 256 or greater colors
  • a vertical refresh rate of 60 Hz, non-interlaced.
  • negative sync polarity on H and V outputs.
  • adjust your system to boot up into 1024x768, 60Hz, with no intervention.

    With your finger on the major video chip of the vide card, reboot and get an idea of how hot the video chip will be under normal circumstances.

    BEFORE connecting the video adapter, adjust the 2K trimpot center tap to ground to a resistor value of 1.5K Ohms. Then leave this alone. Do not adjust this trimpot while powered up or in use.

    Next, use the 200 Ohm trimpot as a variable resistor to attenuate the vertical sync. Set this to almost no resitance, around 5 to 10 Ohms.

    Connect the adapter circuit, BUT LEAVE THE MONITOR DISCONNECTED. Then boot up.

    If possible, look at the signals with an oscilloscope. The horizontal line time should be around 20 uS (microseconds). If not, your video timing is incorrect and the monitor will most likely not sync up.

    With normal operation, the horizontal and vertical sync signals coming directly from your video card should be high (4-5 volts) most of the time. If not, your video card is not generating the negative sync polarity on both H and V signals.

    Shut down, attach the color monitor, and reboot. While booting, rest a FINGER on the VIDEO CHIP of your video card. If it get's too hot, shutdown your system immediately. If it's temperature is OK, then adjust the 200 Ohm trimpot for best signal sync-up. Again, do not adjust the 2K trimpot live.

    GOOD LUCK!


    If building your own circuit and potentially destroying your video card is not up your alley, there are a number of professional video cards which you can purchase to solve the problem (although at a much higher cost). See:
  • Mirage Video Solutions
  • Photon
  • Fixed Frequency Video FAQ

    send comments to Tim Hunkler [click HERE for info on contacting me]