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Thread: Metal foil covered BIOS & Basic EPROM's on Turbo 5160 No Post/Boot

  1. #11
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    * Do you have another PC or XT class computer that you can prove your programmed 27C256 in ? (Info: 27C256 = 32 KB)

    * Just in case of interference, remove the BASIC ROM's. They are not required.

    * In order to simply start and display something, the Supersoft/Landmark diagnostic ROM does not need any of the RAM chips to be fitted. You could remove those as well if you like. (Remembering that bank 0 will be required if you refit the original BIOS.)

    * It looks from the motherboard photo that most, or all, chips are in sockets.
    - If you have not already, re-seat all socketed chips. Look for bent pins, and do not introduce any when putting the chip back. Observe ESD precautions.
    - Verify that all chips are correctly orientated.

    * It is possible that somebody removed chips and put them back in the wrong sockets. You could try comparing the chips on your board to what is shown in the circuit diagram at the rear of the manual pointed to in post #2. For example, in the circuit diagram, U13 is shown as a "LS245", which is a 74LS245.

  2. #12
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    Thanks for the checklist.
    I tested the supersoft in another working XT I have. The Supersoft program works great. It is very good tool to have.
    I removed the BASIC IC's, but not the ram.
    I reseated all IC's, double and triple checked for bent pins. Wrist strap connected, always when working with bear electronics.
    I checked orientation with online pics. All look good.
    I compared IC numbers with similar soldering in IC's on another very similar XT board. Verified any difference with schismatics. All IC's are correct.
    I check all 8088 cpu's on good XT board, all booted supersoft fine and passed tests.

    On first boot with Supersoft, nothing on screen. After about 20 seconds, I heard small sound that sounded like burning circuits, I leaned closer to see what part of the board it was coming from. The sound was coming from the speaker. It quickly grew louder to a full volume buzz. I powered down and checked for warm IC's. The CPU was a bit warm, not hot. all others seemed ok. powered up again, and immediately got the loud buzz sound.
    What would be the next step to see what is happening here? And thanks again for all the help!
    Atari Falcon 030/FX-1 CF & SD 14mb, Atari MSTE, Atari PS3000, STACY 4 /w UltraSatan SD, 4160STE-CosmosEX, Atari PC1-PCH204-2xPCF-551-PCM124, 1040STFM, 1040STF, 520ST(4mb, 16mhz), 400-48K & std kybrd, 800, 600XL, 800XL, 1200XL(256 Rambo,svideo,31-OS,APE upgrade), 130XE, XEGS, matching peripherals for all,
    Apple llGS ROM 3-4mb-CF HD, C64, 4+, IBM XT 5160, IT 99/4+, TRS80-4P, Amiga 500,

  3. #13
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    I used my eprom burner to test as many of 74LSxxx IC's that it could recognize and they all passed.
    I pulled all the RAM. Powered up and still got the buzz.
    I think that just leave the large IC's.
    Thoughts?
    Atari Falcon 030/FX-1 CF & SD 14mb, Atari MSTE, Atari PS3000, STACY 4 /w UltraSatan SD, 4160STE-CosmosEX, Atari PC1-PCH204-2xPCF-551-PCM124, 1040STFM, 1040STF, 520ST(4mb, 16mhz), 400-48K & std kybrd, 800, 600XL, 800XL, 1200XL(256 Rambo,svideo,31-OS,APE upgrade), 130XE, XEGS, matching peripherals for all,
    Apple llGS ROM 3-4mb-CF HD, C64, 4+, IBM XT 5160, IT 99/4+, TRS80-4P, Amiga 500,

  4. #14
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    Quote Originally Posted by KLund1 View Post
    I pulled all the RAM. Powered up and still got the buzz.
    I have come across motherboards that were not starting, and out of the speaker was a constant tone.

    Quote Originally Posted by KLund1 View Post
    I think that just leave the large IC's.
    Noting that there were small chips you could not test using your EPROM burner.
    Some that I can deduce are:
    * U1 (8284A clock/reset).
    * U8 (8288 bus controller).
    * U25 (parity generation) - can be ignored for Supersoft/Landmark operation.
    * U95 (RAM delay line) - can be ignored for Supersoft/Landmark operation.

    Quote Originally Posted by KLund1 View Post
    Thoughts?
    Something else: Verify that there is no jumper on JP1. The circuit diagram shows that it is designed for a momentary contact reset switch, not a jumper.

    And just because it is worth trying, with the motherboard powered, temporarily short out the JP1 contacts (i.e. simulating a momentary contact reset switch) to see if that does anything.

    I have an oscilloscope, and so if I was in your situation, I would be verifying that all clocks are being generated and are as expected (frequency / duty cycle).

    The initial part of the power-up sequence will be:
    1. PSU supplies voltage to motherboard.
    2. After a delay (controlled by C2 and R6), the /RES pin on U1 goes high.
    3. As a result of that, the CPU (and certain other chips) are taken out of the reset state.
    4. As a result of that, the CPU starts execution at address FFFF0h, which an address in the U35 ROM (ROM7).

    So I would be verifying that the /RES pin on U1 is going high, and verifying that the reset pin on the CPU goes low.

    Following that, I would look at the chip-select pin on the U35 ROM (ROM7), expecting to see it go low when the CPU starts execution at address FFFF0h.

    And then I would probably bring out my logic state analyser.

    (Well actually, I have spare 8284A and 8288 chips, and so I would be trying those as a very early step.)

  5. #15
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    Thanks
    JP1 is not shorted. I did short it with power. The buzzing stops, but returns when not shorted.
    I do not have a scope, nor how to use one. So I think I'm pretty much stuck.
    But all is not lost. I learn a lot about these boards, and how to diagnose many potential problems. I learned how to erase & burn eproms, among other things.
    I'll keep this board aside with my notes. If I come across another socketed board, I'll be able to do additional testing.
    Atari Falcon 030/FX-1 CF & SD 14mb, Atari MSTE, Atari PS3000, STACY 4 /w UltraSatan SD, 4160STE-CosmosEX, Atari PC1-PCH204-2xPCF-551-PCM124, 1040STFM, 1040STF, 520ST(4mb, 16mhz), 400-48K & std kybrd, 800, 600XL, 800XL, 1200XL(256 Rambo,svideo,31-OS,APE upgrade), 130XE, XEGS, matching peripherals for all,
    Apple llGS ROM 3-4mb-CF HD, C64, 4+, IBM XT 5160, IT 99/4+, TRS80-4P, Amiga 500,

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