Jump to content

Photo

Shopping list for 600XL upgrades and more.


29 replies to this topic

#26 DrVenkman ONLINE  

DrVenkman

    River Patroller

  • 3,489 posts
  • Back off, man! I'm a scientist.
  • Location:KMBT

Posted Thu Jul 12, 2018 9:52 AM

Don’t use resistance tests. Do continuity tests first instead to verify circuit continuity from each chip shoulder through the socket to the next or the next component leg. Get a cheap (<$20) logic probe and use the logic charts in the 800XL Sam’s (the main chips should give identical results and you can reason around the rest by following traces and asking questions here).

Edited by DrVenkman, Thu Jul 12, 2018 9:53 AM.


#27 seastalker OFFLINE  

seastalker

    Chopper Commander

  • Topic Starter
  • 188 posts

Posted Thu Jul 12, 2018 10:34 AM

I have this multimter: https://www.amazon.c...uct_top?ie=UTF8
 
I don't have the audio icon normally used for continuity. According to https://sciencing.com/use-centech-digital-multimeter-6101228.html there is a trick to check continuity via resistance. I think I just need a better meter and may check shops today.

#28 DrVenkman ONLINE  

DrVenkman

    River Patroller

  • 3,489 posts
  • Back off, man! I'm a scientist.
  • Location:KMBT

Posted Thu Jul 12, 2018 10:41 AM

I have this multimter: https://www.amazon.c...uct_top?ie=UTF8
 
I don't have the audio icon normally used for continuity. According to https://sciencing.com/use-centech-digital-multimeter-6101228.html there is a trick to check continuity via resistance. I think I just need a better meter and may check shops today.


Well, a better meter is rarely a bad idea, but generally should be able to use the diode setting (near the bottom) for continuity tests.

#29 seastalker OFFLINE  

seastalker

    Chopper Commander

  • Topic Starter
  • 188 posts

Posted Thu Jul 12, 2018 11:16 AM

Ok, I found that setting.

 

Do continuity tests first instead to verify circuit continuity from each chip shoulder through the socket to the next or the next component leg.

 

Not to make this 600xl thread now a multimeter tutorial, but does this mean to put one probe on a socket or installed chip's corner leg (the shoulder) and to place the other probe onto each other pin of the chip/socket you are on?



#30 DrVenkman ONLINE  

DrVenkman

    River Patroller

  • 3,489 posts
  • Back off, man! I'm a scientist.
  • Location:KMBT

Posted Thu Jul 12, 2018 11:37 AM

Ok, I found that setting.
 
 
Not to make this 600xl thread now a multimeter tutorial, but does this mean to put one probe on a socket or installed chip's corner leg (the shoulder) and to place the other probe onto each other pin of the chip/socket you are on?


It means - with the system power off - touch one probe to the shoulder of the chip above the socket, and the other probe on the next component that’s connected to that chip pin. The schematics will help but you can also visually trace along the board and find that part or a nearby via on the board. That will verify that the chip leg is actually making good contact with the contacts (“wipes”) in the sockets. Sockets can and do wear out with age due to corrosion, loss of spring tension in the wipe, whatever. So the first test I do now is find out if there’s a potential issue with a socket by checking each chip pin this way.

If those tests all pass, you can power the system and use a logic probe to verify the CPU is getting a good clock signal, that Vcc (power) and Vss (ground) are both connected, that each chip’s address and data lines are pulsing as expected by the system’s published logic chart ... all of this is tedious but it’s thorough and will uncover nearly all basic component or connections f issues that might exist on the board.




0 user(s) are browsing this forum

0 members, 0 guests, 0 anonymous users