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Thread: EAE Troubleshooting Part II

  1. #11
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    During my life in the power plant, I have run into many problems that were the results of the real problem. It's just a manner of time and endurance. Hopefully today and maybe tomorrow I can run some MAINDEC's and verify that my new problem is still on the EAE. Or where ever it is I'll find it. Mike

  2. #12
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    Maybe I should do the cut & jumper on my EAE boards so you can help me debug them.
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  3. #13
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    Not sure what 'cut & jumper' is, but am always willing to help. MIke

  4. #14

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    Quote Originally Posted by m_thompson View Post
    We have run into this numerous times fixing DEC equipment where a broken chip hides the broken chip behind it.
    Oh yes. I have just repaired two 4K M8311 MS8-A memories. Both boards had multiple failures. When I have fixed DEC equipment that has been stored for years it's pretty common that I fixes one problem and things works for a while, then it breaks in another place.

    Just keep it up!

  5. #15
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    Quote Originally Posted by Mike_Z View Post
    Not sure what 'cut & jumper' is, but am always willing to help. MIke
    There are several different revision levels for the M8340/M83401 that have to be matched to the revision levels of the M8310 and M8330. My EAE is an early revision. One of the grounds on the over-the-top connectors was changed to a signal on a later EAE board revision. If I install the EAE boards that I have it kills the processor. I need to cut the ground connection and wire the gold finger to a signal to make it like the newer revision EAE. Hopefully that is the only design change and I can get them to work with the newer processor boards.
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  6. #16
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    Interesting, how do you tell what version of EAE one has. I have downloaded the schematics from bitsavers and have noticed that my boards are a little different. For example, there is a tri state buffer on the MQLOAD output. Must have been an improvement. I have ran a few MAINDEC's yesterday and they passed. I think the trouble is still on the EAE boards, but I want to run the rest of the MAINDEC's to be sure. Mike

  7. #17
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    The letter after the part number on the back of the PCB is the PCB's revision level. The letter stamped into the back of the plastic handle is the assembly's revision level.

    The schematic title block contains the assembly's revision level, "F" for the M8340 schematic and "E" for the M8341 schematic that I just looked at.
    Sometimes the assembly drawing calls for one or more PCB revisions, and then lists the cuts & jumps that are required to bring the assembly up to the current revision.
    Sometimes the title block contains the PCB and assembly revisions.
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  8. #18
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    Yesterday I finished up with the MAINDEC routines. The machine is OK and the divide is bad again. I was suspicious of my new replacement chip. When I replace a chip on this machine I always install an IC socket. I removed the chip and put it on a breadboard and tested it. It was bad. Apparently there are two things to think about, one, maybe the first chip was not so good and failed right away, or there is something else on the board that is burning this chip. Turns out that this replacement chip did not fail in the same manner as the first chip. A different output was open, so on a flyer I thought I'd try a different chip. The machine has been operating for about 5 hours and this new chip is working. I ran D0MB (EAE MUL & DIV) for a bunch of cycles and there are no errors. So, maybe I lucked out. I thought that I'd take some time to make a few waveform charts with the logic analyzer for future use. I started with the Quotient bit, MQ11.

    Here is a simplified circuit diagram
    MQDATAcircuit.jpg

    Here is the wave form. The labels are a little hard to see. They are, top to bottom, DVI used as a trigger, SC=0, MQ10, DIVLINK, CARRYOUT, MQDATA and MQLOAD. MQ11 = DIVLINK XOR MQ10 XOR CARRYOUT
    MQDATA.jpg

    I used my short divide program and the Maintenance Manual Vol 2 example of 221 (Octal) divided by 14, which results in 14 with a remainder of 1. I checked the waveform against the example and it compares. Although the DIVLINK seems to be compliment.

    I'll post a few more wave forms as I get them. Mike

  9. #19
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    Here is the adder link bit. The MQ0 bit is shifted into the AC0 bit. This has to be with respect to the complimented state of the accumulator. The Adder Link is MQ0 XOR MQ11. MQ11 is anded with EAE On.

    Here is the simplified circuit.
    ADLKcircuit.jpg

    Waveform
    ADLK.jpg

    Mike

  10. #20
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    Here is the Divide Link. This replaces the normal Link. There is a disable link circuit which does the switch. The Divide Link is the adder bit 0 or signal bit.

    This is the simplified circuit.
    DivideLinkCircuit.jpg

    Waveform. The labels are DVI, AD0, ACLOAD and DivLnk.
    DIVIDELINK.jpg

    The values match the example. Mike

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