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XT Clone trouble - no boot, no post

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    XT Clone trouble - no boot, no post

    Dear Experts

    first a thanks to you all here as i could find a lot of information and already have at least a picture on the screen. But now I'm somehow stuck. As mentioned it's a clone and i did check already Power Supply (also swapped with known good one) desoldered the leaking battery (traces are still good) removed all cards - nothing. Thougth on the Bios Eprom failed and luckily found some images that should match (COPAM TD3.86 from Thomas Lao)
    I read about the Supersoft Rom to diagnose - so i programmed and installed. First Success i have something on screen telling me that the 8253 Timer Channel 1 failed and Memory. I setup an Arduino to test the DRAM's (http://www.chronworks.com/DRAM/) so far all good or not that faulty as the Diag Rom tells me. Tried also to just populate Bank1 with good tested M5M4256 with no success. Not sure if i understood that correct but the Timer also is related to the Memory ? if so, it would explain that many errors.
    Searching for the 8253 on the Board ... nothing but there's an MM57167AN.

    Now to my question before i start to solder this one out. Could this be the one causing the Timer and Memory Failure ?

    BR and thanks for any hint to bring this back to life
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    This gallery has 4 photos.

    #2
    No, that is the realtime clock. It has nothing at all to do with the 8253 programmable interval timer.

    In this case, this motherboard does not have a 8253 chip. Instead all of that is implemented in that big VLSI chip. It may even be that a failure on that channel 1 test is normal for this chip - but there is no way to be certain unless it was compared to a known good clone of the same model.

    Now, the ram test should darn well pass if the chips are good. So there is something wrong there. If your original ROM was damaged by the leaky battery, then I would still strongly suspect a broken or shorted connection in that general area. Although from that picture, it looks in very good condition.

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      #3
      Thanks for the information. Just looked at the Datasheet of the FE2010A and read this : Channel 1 is directly connected to the DMA channel 0 request line and provides timing for the Dynamic RAM refresh. Seems pretty what I expirience from the test. So i will try to get hands on a known working one.

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        #4
        Originally posted by wonder View Post
        I setup an Arduino to test the DRAM's (http://www.chronworks.com/DRAM/) so far all good or not that faulty as the Diag Rom tells me. Tried also to just populate Bank1 with good tested M5M4256 with no success.
        I am certainly not an expert but did you test for proper voltage on every dram socket? I had an issue once where one dram socket wasn't getting voltage and it took forever to figure out - all I had to do was reflow the socket. Sorry I can't be more helpful - I am certainly not an expert like others here.

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          #5
          Thanks chjmartin2, i will also check on this. In the meantime i could test a DRAM's and one was marked as bad. Hope that i can test them in deep when i get hands on a FE2010A - not that easy to find here in Switzerland. Looking currently in the US

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            #6
            I am working on a couple clones with the fe2010a I got one of the boards working 100% and it fails the timer 1 test so I believe that is normal for the fe2010a, so now I am trying to get the second board going , unfortunately all the dram is soldered. It will freeze anywhere from the dma test to the end.
            Last edited by Klyball; October 10, 2021, 07:49 PM.

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