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Thread: Troubshooting just died vaxstation 3100-30 motherboard

  1. #1

    Default Troubshooting just died vaxstation 3100-30 motherboard

    My vaxstation 3100-30 suddenly stopped working while I was trying different configurations by plugging/pulling memory and graphic boards. It now stops early in power up test with LED's showing code 1111-0000, right after briefly showing 1111-1111 -- that is with all board removed from the motherboard.

    Before that the system worked quite reliably running vms and ultrix. It would be a shame to leave this board dead without at least trying to resurrect it.

    I was not able to find any schematics of the motherboard board, nor even pinout of the CPU, so it seems very problematic to approach troubleshooting of the board in its current state. I guess the best I can do now is to hook logic analyzer to ROM chip pins.

    But maybe someone here could give a better advice or even some technical info, which would be greatly appreciated.

    Thanks

  2. #2

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    This should help you a ton if you start trying to diagnose things, https://vaxstuff.files.wordpress.com...ance-guide.pdf

    From the sounds of it, something's happened to the mainboard ROM based on your LED output.

    That being said, follow the troubleshooting guide in Appendix G.1 in that manual.

  3. #3

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    Thanks for the link to the maintenance guide. The guide is going into troubleshooting down to failing FRU level only, which is where I stopped - I know that failing FRU is the motherboard (system module). Well, technically it could be power supply also, but I did check voltages, appears to be ok.

    The LED code means "Power is applied. The ROM code is successfully started and several instructions have been executed." Not quite informative but something. I read it so that it executed the start of powerup program and did produce output into LED control circuitry and then hanged for one of million possible reasons.

    I actually would suspect mechanical breakage of some circuit on the board, because plugging/unplugging the peripheral boards that lead to failure was accompanied by moderate bending and stressing of the motherboard due to design of those connector - they are of SIF type (Significant Insertion Force). Every time replacing board I cringed from creaks the board produced which sounded like impeding trouble.

    So I did reseat all chips that are on sockets but that did not help. I would not be surprised if some trace on the board cracked - such failure would be very hard to discover without guidance that schematic could provide.

  4. #4

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    I know what you mean about the plugging/unplugging of the various boards; most MicroVAX/VAXserver/VAXstation 3100s all used the style. You really need to take your time if you're swapping a lot.

    It could definitely be a breakage somewhere and I have never found the schematics, so I have to assume they're not online, at least we've got the maintenance manual which wasn't online for a fairly decent amount of time.

    At this point, if the 3100 is not getting past that particular state with no RAM or graphics coprocessor on it, then it's either doing electronics debugging on the board or buying a used one off eBay to get things back in order.

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