Socketed ANTIC and ...

[+Stephen]

I'm doing some work on my PAL 130XE. I removed the PoKey & socketed it. Machine powered up and did the self-tests fine. Next on the list was the ANTIC. Socketed the mainboard, reinstalled the ANTIC and the machine powered up fine. Went into self-test and started the Audio-Video test. It cycled through the 4 voices fine. I hit the help key to go back to the main menu and the screen garbled. Now the machine won't even boot back up. I have a 130XE diagnostic cart. It returned a system error 7 (memory failure during RAM refresh check using pattern 00). The machine comes up with a red screen, black borders. It does sync to a stable screen.

 

Any ideas what went wrong? I don't think I fried ANTIC when removing it because the self test initially worked.

 

Stephen Anderson

[Rybags]

I'd guess an intermittent bad connection, probably on an Address line.

 

Fairly easy to test, just multimeter test the corresponding pins on Antic to the ones on the CPU.

That should cover 75% or so of the pins (A0-A15, D0-D7, NMI etc)

 

A stable screen (not rolling) at least indicates that Antic is still controlling the screen timing. GTIA requires Antic to tell it to do VSync.

[+Stephen]

I'd guess an intermittent bad connection, probably on an Address line.

 

Fairly easy to test, just multimeter test the corresponding pins on Antic to the ones on the CPU.

That should cover 75% or so of the pins (A0-A15, D0-D7, NMI etc)

 

A stable screen (not rolling) at least indicates that Antic is still controlling the screen timing. GTIA requires Antic to tell it to do VSync.

All address lines and data lines and NMI are connected from top of CPU to top of ANTIC. However, I noticed that O2 aren't connected (pin 39 of CPU to pin 29 of ANTIC). Is this the same signal or do these pins not need to be connected?

 

Stephen Anderson

[+warerat]

I'd guess an intermittent bad connection, probably on an Address line.

 

Fairly easy to test, just multimeter test the corresponding pins on Antic to the ones on the CPU.

That should cover 75% or so of the pins (A0-A15, D0-D7, NMI etc)

 

A stable screen (not rolling) at least indicates that Antic is still controlling the screen timing. GTIA requires Antic to tell it to do VSync.

All address lines and data lines and NMI are connected from top of CPU to top of ANTIC. However, I noticed that O2 aren't connected (pin 39 of CPU to pin 29 of ANTIC). Is this the same signal or do these pins not need to be connected?

 

Stephen Anderson

 

PHI2 is buffered through an AND gate on the 130XE. You should have continuity between pin 29 of ANTIC and pin 3 of U18 as also pin 39 of the CPU and pin 1 of U18.

[+Stephen]

 

PHI2 is buffered through an AND gate on the 130XE. You should have continuity between pin 29 of ANTIC and pin 3 of U18 as also pin 39 of the CPU and pin 1 of U18.

Thanks - they both verified. I have now verified all pins.. Everything checks fine. Machine still won't boot. It would be on hell of a coincidence if the memory all of a sudden went bad after socketing ANTIC. I can't find any bad connections though.

 

Stephen Anderson

[+Stephen]

OK - out of desperation I gave it a good bath in super hot water, scrubbed it down with some detergent, rinsed then blew dry with compressed air. It's booted up into BASIC Doesn't react well when the reset key is hit. Not sure what's going on with this - it's "flaky" for now.

 

Stephen Anderson

[Rybags]

Normally you should leave it to dry somewhat longer if you give it a bath.

 

Maybe put it aside for a day or so then try again.

 

Also, were you testing connections from the IC pins or the sockets? I noticed on some of my gear - the pins start to oxidize which affects conductivity.

 

An aerosol can of circuit board/contact cleaner is a good idea in that case.

[+Stephen]

Normally you should leave it to dry somewhat longer if you give it a bath.

 

Maybe put it aside for a day or so then try again.

 

Also, were you testing connections from the IC pins or the sockets? I noticed on some of my gear - the pins start to oxidize which affects conductivity.

 

An aerosol can of circuit board/contact cleaner is a good idea in that case.

It was dry - used compressed air to dry everything. I was testing the connections from top of IC to top of IC. That way I know for sure the connection is good through the socket.

 

The keyboard on this unit seems a bit flaky - I am hoping that is what's causing the reset issue.

 

*** EDIT ***

Suspicions confirmed - I plugged in my known good keyboard from my main 130XE. All was fine. Did some BBSing with no problems. Now I can move on with the mods.

 

Stephen Anderson

[flashjazzcat]

Suspicions confirmed - I plugged in my known good keyboard from my main 130XE. All was fine. Did some BBSing with no problems. Now I can move on with the mods.

That's great news Stephen. I know it can be bloody maddening when ancilliary problems hamper a project right from the get go like this. Looking forward to seeing this super machine.