(Topic ID: 63363)

How to figure out if 6821 chip is bad with a DMM?


By Choggard

6 years ago



Topic Stats

  • 17 posts
  • 10 Pinsiders participating
  • Latest reply 2 years ago by oldschoolbob
  • No one calls this topic a favorite

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    #1 6 years ago

    Is there a way to do this?

    #2 6 years ago

    Certain results would definitely indicate it was bad.

    Can you figure out if a 6821 chip is good with a DMM? No.

    #3 6 years ago

    You need software running to fully test a PIA. In a bally -35 mpu, the power on self test catches bad PIAs about 95% of the time.

    #4 6 years ago

    For a $4 part, replacing it seems like the quickest test.

    #5 6 years ago
    Quoted from Noahs_Arcade:

    For a $4 part, replacing it seems like the quickest test.

    Disagree. If someone doesn't understand how to test a PIA, they shouldn't be desoldering a 40 pin IC and soldering a new socket in. That's a lot of chances to mess something up.

    Be sure the part is bad, before you replace it.

    Testing these, for the most part, is pretty straightforward with a test ROM, logic probe and power supply.

    #6 6 years ago

    As has already been mentioned in your original thread, you need a logic probe.

    #7 6 years ago
    Quoted from dsuperbee:

    As has already been mentioned in your original thread, you need a logic probe.

    NEED MOAR THREADS

    #8 6 years ago
    Quoted from johnwartjr:

    That's a lot of chances to mess something up.

    I agree, but people are more likely to grasp soldering than semiconductor physics.

    #9 6 years ago

    Totally agree with John here except in the case where the PIA is already socketed and you have a known good PIA in hand. Of course if you suspect a bad PIA in a socket on a Sys11 it's likely been replaced once already and you have to suspect prior work. At that point a test ROM and logic probe will come in handy...

    viperrwk

    4 years later
    #10 2 years ago

    Bringing back a really old thread - PIA's are getting hard to find and I'm getting a collection of them with "?" on them.

    Could someone explain in more detail how to test PIA's.

    I have a bench tester and can get all seven flashes. I have a logic probe and a USB oscilloscope - but I don't know much about using them.

    Thanks

    Bob

    #11 2 years ago

    The neoloch tester with the PIA blade module will test them.

    #12 2 years ago

    WOW - 300.00 to test PIA's???

    I can buy a lot of PIA's for 300.00

    I was hoping to find someway to use the equipment I already have.

    But thanks for the suggestion.

    Bob

    #13 2 years ago
    Quoted from oldschoolbob:

    WOW - 300.00 to test PIA's???
    I can buy a lot of PIA's for 300.00
    I was hoping to find someway to use the equipment I already have.
    But thanks for the suggestion.
    Bob

    Where are you seeing that?

    http://www.neoloch.com/products/Inquisitor.php

    $184.90 for the core, power supply and the 3 blade modules (though you probably wouldn't use the DRAM module).

    Or the core and PIA blade for $98.90, and power supply for $9.85--$108.75 plus shipping.

    Or, get the kit version a bit cheaper and solder it together yourself.

    #14 2 years ago
    Quoted from oldschoolbob:

    WOW - 300.00 to test PIA's???
    I can buy a lot of PIA's for 300.00
    I was hoping to find someway to use the equipment I already have.
    But thanks for the suggestion.
    Bob

    I think Bally MPU is a pretty good place to check PIAs. The software for those games has a pretty reliable power on self test. Then in game play mode every port is used between U10 and U11 (I think). U10 the PA ports are used as reading switches and at U11 the PA ports drive solenoids and etc. If the PIA passes the power on self test and works properly at U10 and U11 it is 99% tested good. It is something you may already have on hand.

    #15 2 years ago

    Sorry ForceFlow, I wasn't sure what a core or blade was. The first time I looked I thought I needed one unit for 184.90 and another unit for testing PIAs for 98.90 plus the power supply for another 9.85 - plus shipping. But now I see the core and blade bundle is all I need for 98.90. That's more reasonable. And the kit is only 68.90. (I enjoy building kits). I read the kit instructions and they don't look too difficult. (no SMD's)

    Do you have this neoloch tester? Do they test everything on the PIA's? I'm seriously thinking about ordering one. Where are they located. (please don't be China).

    Thanks

    Bob

    #16 2 years ago
    Quoted from oldschoolbob:

    Do you have this neoloch tester? Do they test everything on the PIA's?

    Yes to both.

    Quoted from oldschoolbob:

    Where are they located.

    It's a US seller.

    1 week later
    #17 2 years ago

    Thanks for the info on Neoloch. I just finished building the kits - easy to build.

    I had 7 PIAs that were questionable. 2 tested bad and 5 tested good. I feel much better now.

    Bob

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