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Thread: Exidy Sorcerer error

  1. #41

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    It's maybe hard to see, but I'm actually measuring the caps between + and - . Every beep = connectivity between those points which shouldn't be according to my knowledge (at least, not for tantalum caps). Others don't do that while on the same setup (and even same value).
    I have a few computers and only have 612m2 for computers.

  2. #42
    Join Date
    Mar 2013
    Location
    Chaffee, MO
    Posts
    1,023

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    whizzi,
    Let me state it another way. Pick one cap that beeps, and unsolder it and remove it. See if the Motherboard Pads still Beep,
    and the Cap checks good on a Cap checker. (If you were to power up the Motherboard, then the caps that beep would have ZERO
    volts across them, since they are a short. I'd think the 5 VDC line being shorted in that many places would be more than the
    Power Supply could provide. It would blow a fuse or shut down for current limit. )

    Larry
    Last edited by ldkraemer; September 20th, 2018 at 08:53 AM.

  3. #43
    Join Date
    Mar 2013
    Location
    Chaffee, MO
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    1,023

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    Bart,
    You haven't posted in a while. I was just wondering how you are progressing. I sure didn't mean to piss you off. If I did, I apologize.

    Let us know how you are progressing on the Sorcerer.

    Larry

  4. #44

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    I've been busy with other machines in the museum, like an Amiga 1000 (had to create a Kickstart disk), fixing the Amiga 1081 monitor for it, setting up an Atari Mega ST, fixing our LAN-computers so they can play Quake III and NFS 2 (with steering wheel).

    The Exidy is actually on the planning for today so more updates today
    I have a few computers and only have 612m2 for computers.

  5. #45

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    allright, I removed 1 tantalum capacitor that was shorting (marked C93) and after removal, the tantalum responded correctly to continuity (as in, one short beep and then nothing) and the board was still having continues between the 2 point where the capacitor was.

    So, back to square 1. Why is the Exidy not seeing or addressing it's memory. I think I need to find myself the schematics and perhaps the oscilloscope to figure out why.
    I have a few computers and only have 612m2 for computers.

  6. #46
    Join Date
    Mar 2013
    Location
    Chaffee, MO
    Posts
    1,023

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    Whizzi,
    You problem is that it's something along the 5 VDC buss that is shorted. You need a way to chase the actual current flow
    across the board to the problem IC or Component. One easy way to do it is with FREEZE MIST, assuming you have lots
    to spray on the PCB as it heats from a LAB Power Supply set for a very LOW Voltage with Current Limit set way down on the
    LAB Supply.

    But, a better way I'd suggest to locate your short or current path would be to inject a low current by using 2 "D" cells in series with two
    3.9 OHM Series resistors. That should get you 3 VDC at ~380ma to use as current path to trace where the current is going on your
    motherboard. You should be able to take a Voltmeter and set it to millivolts and just trace along the 5VDC circuit trace and locate
    the lowest voltage along that path. It the voltage doesn't change, there is no current flowing on that PCB trace. Select a different one.
    That should get you to the problem quicker than mass replacement. If you remove all the RAM IC's it would even be a better test,
    assuming they are in IC sockets.

    Larry

  7. #47

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    Thanks for the answer Larry.

    The memory is socketed and in fact, I removed the entire memory from the board and it still starts up, acting exactly the same. It probably runs on it's videoRAM at that point. The question is, why is the memory not being seen and used while it's there.

    I first thought the tantalum since they were giving continuity, but that's debunked this afternoon when I desoldered one which acted as it should while the board still gave continuity between + and - of that tantalum.
    I have a few computers and only have 612m2 for computers.

  8. #48

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    Responding to a query posted on StarDot:

    My Sorcerer had a short circuit on the 12v rail which was caused by a tantalum capacitor. The way I resolved it was to desolder one leg of each capacitor until the short circuit went away, then replace any tants that were faulty. It's easy enough to do this, even working from the component side of the board (especially if you have a decent soldering iron).

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