Strange leon test rom behavior with sys 7

(Topic ID: 198798)

Strange leon test rom behavior with sys 7


By supermoot

1 year ago



Topic Stats

  • 11 posts
  • 5 Pinsiders participating
  • Latest reply 1 year ago by MarAlb
  • Topic is favorited by 3 Pinsiders

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    #1 1 year ago

    Leon's test rom's flashes get faster and faster and then it crashes. It happens in less than a minute. Seems to be slower if I give it some time between tries.

    Board on the bench would not boot. 7404 at IC7 was smoking hot, so I replaced that and leon's would boot. Ram test was sad about the 5101 at IC19, replaced, still read bad. The 7408 at IC12 was bad, replaced, ram tested good. Started to continue testing but then the speed up problem started happening. Tried no ram and a different 6808 to no avail.

    I'll get it jumpered up for Andre's next, but wanted to see if anyone has seen something like this or had any ideas.

    #2 1 year ago

    Hi,
    It look like a clock problem, and testing with another 6808 was a good idea. But, does the Phi2 signal (on pin 37 / 6808) stable ? did you check it using a scope ?
    I sometimes encounter strange clock behaviour (like a divide by 3 using a 7474 on 6502 systems ! ) and checking the clock at Phi2 is a base for repairing.
    May be, a good idea will be to replace the XTAL (CR1, 3.579 Mhz) and the two associated capacitors (C25 and C26, 27pF). A defective capacitor may lead to an unstable clock signal.

    #3 1 year ago

    Another testrom which you can get from me for free

    #4 1 year ago
    Quoted from MarAlb:

    Another testrom which you can get from me for free

    wow i didnt know you did one.. if its half as good as your gottlieb one i would pay for..

    #5 1 year ago
    Quoted from wiredoug:

    wow i didnt know you did one.. if its half as good as your gottlieb one i would pay for..

    Thanks Doug, you've got some email.....

    For everyone who wants to try the Williams testrom, please send me a PM with your email address. The video above is obsolete as I tweaked the testrom over the years a few times. Compared to Leons' testrom it has some more reliable memorytests, it tests the IRQ generator, it has an input test for the switchmatrix PIA, it has a PIA init test and it can test the U14 and U20 rom sockets with an additional testrom. In a nutshell. Due to the additional tests it might be a bit more difficult to work with.

    Andre's testrom is also a nicely programmed testrom for Williams which can obtain good results.

    Marco

    #6 1 year ago

    Here's my math..

    Marco's Test ROMs > Other Test Roms

    #7 1 year ago
    Quoted from noflip95:

    Hi,
    It look like a clock problem, and testing with another 6808 was a good idea. But, does the Phi2 signal (on pin 37 / 6808) stable ? did you check it using a scope ?
    I sometimes encounter strange clock behaviour (like a divide by 3 using a 7474 on 6502 systems ! ) and checking the clock at Phi2 is a base for repairing.
    May be, a good idea will be to replace the XTAL (CR1, 3.579 Mhz) and the two associated capacitors (C25 and C26, 27pF). A defective capacitor may lead to an unstable clock signal.

    Before drifting off to sleep last night I was all "ooh maybe the crystal section". I've got one and the caps on the way. I only have a logic probe, perhaps it's time to start looking at scopes. Thank you so much for your help! I will be back with results.

    #8 1 year ago
    Quoted from acebathound:

    Here's my math..
    Marco's Test ROMs > Other Test Roms

    true true... and its teamwork with another guy who made this PCB.. i think you know him
    http://pinitech.com/products/gottlieb_universaltester.php

    #9 1 year ago
    Quoted from wiredoug:

    true true... and its teamwork with another guy who made this PCB.. i think you know him
    http://pinitech.com/products/gottlieb_universaltester.php

    Also want to state, no disrespect meant on the other ROMs. They've been an evolution over the years like everything else.. and people doing the TEST ROMs were inspired by the work done by others before them. It's just that Marco's TEST ROMs have far surpassed capabilities in just about anything Marco has a ROM for. I haven't personally used too many of the other ROMs *yet* -- been a while since I tackled repairing a bunch of MPUs, but there's a local repair guy near me that out-of-nowhere continues to compliment this Sys80 tester. Probably a dozen times now, it's like one of the best things ever in his eyes haha. I always tell him most of the credit goes to the guy that wrote the software He's also used other Marco ROMs and has said everything he's used has been awesome. I definitely think Marco should be proud of all his hard work and that others are finding the TEST ROMs so useful!

    Just wanted to say that proceeds from sales of any Marco EPROMs purchased from PINITECH are directly donated to Marco once the EPROM cost is paid for. My way of giving back to him since he's pretty humble and hasn't asked for any $$ from anyone that's wanted the ROMs. Plus, the Sys80 Tester really isn't much without his awesome software

    #10 1 year ago

    After replacing the crystal and two caps, the behavior continued. Upon reflection it did not start until I replaced the 7408 in the memory protect circuit to get the 5101 going. I had cannibalized it off a sys 6 board, and ordered a few 74f08's to replace. I threw a new 74f08 in on a whim and the behavior disappeared. I have no idea.

    I tried both chips with Marco's test chip and it was not influenced differently.

    What a great program! It was a joy to use. Thanks for your hard work!

    #11 1 year ago

    Nice! Thanks for your feedback. Certainly a lot of work but really worth it!

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