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Thread: 520STm Boot Issues

  1. #1

    Default 520STm Boot Issues

    I purchased a power supply and composite cable off ebay and now that they have arrived it is time to test. I don't have a floppy attached yet but I expected to see a "Put your Systems Disk int your Disk Drive" when turned on. Using a RF modulator plugged into a TV, I get snow, then after turning the 520STm on, get a black (or dark gray) screen for a few seconds, followed again by the snow screen. I have re-seated all of the socketed chips already.

    Your troubleshooting suggestions would be appreciated.
    - Don Mankin -

    [
    TRS-80 Models I, 4, 4p, Coco 2, 100, 102. Tandy 1000 RLX. Osborne 1a.
    At
    ari 800, 520 STm. Commodore 64.
    Amiga 1000. TI-99/A. Sinclair ZX-81]

  2. #2

    Default

    Except for the very earliest version, the Atari 520ST has its operating system (TOS) in ROM, so if you don't have any floppy drives (either built-in or external), the GEM Desktop should appear within a few seconds after turning it on. If you do have a floppy drive, it will take a while longer as it checks for a disk with startup/configuration files on it, but the Desktop should eventually appear after 15-20 seconds or so.

    Even if you do have the earliest version without TOS in ROM, it should show a boot screen that mimics the appearance of the GEM Desktop:



    And if I understand your setup correctly, you bought a cable that connects to the Atari's large round DIN video output port and provides a composite video output, and you're connecting it to an external RF modulator and then to a TV set. But if you need an RF output rather than composite video, why not just use the RF modulator that is built in to the computer? Have you tried it instead?

  3. #3
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    Quote Originally Posted by vwestlife View Post
    And if I understand your setup correctly, you bought a cable that connects to the Atari's large round DIN video output port and provides a composite video output, and you're connecting it to an external RF modulator and then to a TV set. But if you need an RF output rather than composite video, why not just use the RF modulator that is built in to the computer? Have you tried it instead?
    Nothing to add to what vwestlife said as far as the boot process/timing/etc.

    A quick addendum to the RF piece. If you have a composite cable for the ST (the one that connects to the large din connector on the ST), then that needs to be connected to a composite connection (yellow) on the TV and the TV has to be set to composite video. In order to use RF, there's likely a piece missing. First, as vwestlife said, you can use a regular RCA cable to plug into the modulator on the ST, however the other end will likely need to be connected to a 'RCA to Type F' connector which then connects to the coax connector on a modern TV (modern being anything in the last 20 or so years). Also, the TV needs to support antenna and not just digital cable.
    -- Brian

    Systems: Amstad PCW 8256, Apple IIe/II+/Mac+/Mac 512k, Atari 800/520STFM, Commodore 64/Amiga 3000/PET 4032/SX-64, IBM PS/1 2121-B82, Kaypro II, Osborne 1, Tandy 1000 SX, TI-99/4A, TRS-80 Model 4 GA

  4. #4
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    Whilst TOS is in ROM doesn't it get confused if no floppy at all...
    Dave
    G4UGM

    Looking for Analog Computers, Drum Plotters, and Graphics Terminals

  5. #5
    Join Date
    Sep 2012
    Location
    Indiana, USA
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    500

    Default

    I have a 520 ST currently setup. The original form factor with TOS in ROM, an external power supply, and no internal floppy drive. I just tried booting it up with the floppy drive disconnected, and after a few seconds it comes to a blank GEM desktop.

  6. #6

    Default

    Frankly I don't know if I have the earliest model with TOS in rom or not. I was hoping to be able to tell by what showed on the screen after boot.

    Due to storage limitations, rather then have a plethora of monitors hanging around, I use a tried and true RF modulator / TV configuration on all my vintage computers. I've thus far been successful at fixing them all... knock on wood. This is the last one not yet working.

    I tried the Television port. I'm a little confused by the L / H switch and what channel to put the TV on, but I tried all combinations and could not get a signal. Maybe a bad cap?

    I also was concerned that, if I had the early model, the boot process might just fail if it couldn't see a floppy drive to load TOS from. I've found a Samsung SFD-321B and modded it for DS0. I also built a external drive cable based on this discussion: http://www.atari-forum.com/viewtopic.php?t=26656. This introduces another point of failure risk since I might have screwed up the cable but at this point is sounds like I need to follow though and give it a whirl. What's the worst that can happen? <grin>
    - Don Mankin -

    [
    TRS-80 Models I, 4, 4p, Coco 2, 100, 102. Tandy 1000 RLX. Osborne 1a.
    At
    ari 800, 520 STm. Commodore 64.
    Amiga 1000. TI-99/A. Sinclair ZX-81]

  7. #7

    Default

    I've also considered replacing the 6 ROM TOS. I've read (conflicting) posts that I can simply replace the roms with TOS 1.02 or 1.04 if they are still available. Since the floppy loaded TOS takes up valuable 512K memory, this sounds like the way to go anyway. It would also eliminate the question of if it needs a working floppy connected. Of course, I may already have a ROM based TOS so it may be a waste of money.

    If I had some ham, I'd have some ham and eggs... if I had some eggs!
    - Don Mankin -

    [
    TRS-80 Models I, 4, 4p, Coco 2, 100, 102. Tandy 1000 RLX. Osborne 1a.
    At
    ari 800, 520 STm. Commodore 64.
    Amiga 1000. TI-99/A. Sinclair ZX-81]

  8. #8

    Default

    Quote Originally Posted by Fooser View Post
    I tried the Television port. I'm a little confused by the L / H switch and what channel to put the TV on, but I tried all combinations and could not get a signal.
    That's the channel selector switch. I know the older 8-bit Atari computers output on either channel 2 or 3, but I don't recall if that's also true for the ST series or if they use channels 3 and 4 like most other 1980s systems.

    Try connecting the audio output of your composite video cable to an audio amplifier and speaker. Even if the video signal isn't working for some reason, if the computer is running you should hear key clicks coming from the speaker as you press keys on the keyboard.

  9. #9
    Join Date
    Apr 2018
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    Quote Originally Posted by Fooser View Post
    I've also considered replacing the 6 ROM TOS. I've read (conflicting) posts that I can simply replace the roms with TOS 1.02 or 1.04 if they are still available.
    If you have TOS Rom chips, then you're good. You shouldn't need to boot to a TOS floppy at all, so that isn't your problem... The machine should come up to a screen after about 20 seconds. Even without TOS in rom, you should be at least getting a solid screen, so if you're getting static still, theres another issue. As an aside, if you have an Eprom burner, you can burn 1.04 roms pretty easily or they are also available on ebay.

    One thing to note on early STs, the composite cable only works if the RF modulator works. It's why (and getting into a slight tangent) that ST's without a modulator don't work with composite cable either. There are other ways to get video on the ST with a regular LCD, but it requires about $60 in parts (a specific SCART HDMI box and a SCART ST cable). i can link that or i've linked it in other threads.

    As for the modulator, I believe the H/L switch on there is Channel 3/4... Just wanted to confirm that you are using a cable directly from the ST into the back of a TV? You don't need any RF modulator box, because the ST is doing that directly with its built in box. You should connect a standard RCA cable from the back of the computer into a "RCA to type F converter" and then screw that connector onto the Antenna port on your tv. Set the tv to 3/4 (maybe 2, can't recall) and flip the switch accordingly.

    connection.jpg
    -- Brian

    Systems: Amstad PCW 8256, Apple IIe/II+/Mac+/Mac 512k, Atari 800/520STFM, Commodore 64/Amiga 3000/PET 4032/SX-64, IBM PS/1 2121-B82, Kaypro II, Osborne 1, Tandy 1000 SX, TI-99/4A, TRS-80 Model 4 GA

  10. #10

    Default

    Quote Originally Posted by ngtwolf View Post
    One thing to note on early STs, the composite cable only works if the RF modulator works. It's why (and getting into a slight tangent) that ST's without a modulator don't work with composite cable either.

    As for the modulator, I believe the H/L switch on there is Channel 3/4... Just wanted to confirm that you are using a cable directly from the ST into the back of a TV? You don't need any RF modulator box, because the ST is doing that directly with its built in box. You should connect a standard RCA cable from the back of the computer into a "RCA to type F converter" and then screw that connector onto the Antenna port on your tv. Set the tv to 3/4 (maybe 2, can't recall) and flip the switch accordingly.
    I connected to the built in modulator exactly as you described. Interestingly enough, the built in modulater showed no recognizable signal, where as the composite monitor cable to an external modulator briefly showed a dark screen, for about 4 seconds, before the static snow returned.

    Quote Originally Posted by ngtwolf View Post
    There are other ways to get video on the ST with a regular LCD, but it requires about $60 in parts (a specific SCART HDMI box and a SCART ST cable). I can link that or i've linked it in other threads.
    Yes, thanks, I would be interested in the link.

    Quote Originally Posted by ngtwolf View Post
    If you have TOS Rom chips, then you're good.
    Is there a way to tell (without a working monitor) if I have TOS in ROM? I have these 6 chips in sockets.

    U7,C026165-001,RP23256,0155,5M4,A0
    U6,C026164-001,RP23256,0154,5M4,A0
    U5,C026163-001,RP23256,0153,5M4,A0
    U4,C026162-001,RP23256,0152,5M4,A1
    U3,C026161-001,RP23256,0151,5M4,A0
    U2,C026160-001,RP23256,0150,5L2,A6
    - Don Mankin -

    [
    TRS-80 Models I, 4, 4p, Coco 2, 100, 102. Tandy 1000 RLX. Osborne 1a.
    At
    ari 800, 520 STm. Commodore 64.
    Amiga 1000. TI-99/A. Sinclair ZX-81]

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