Asteroids PCB for CNP - fix log

[Nes4life]

Got an 'untested'

Asty PCB from CnP and boy did it need some work to get going!
[list type=decimal][*]Inspection:

• DIPS need replacing (replacement not pictured)
• Crystal (for main clock) is missing!
• Thump capacitor missing
• A few broken traces need patching
• Variable resistor for Y output is broken

[*]After fixing / replacing above; still dead - no Watchdog

• Replace LS74 at D4 to restore Watchdog

[*]Watch-dogging in test mode!

• Lift pin 1 of L6 to test the logic section independently
• watch-dogging still
• Connect Arduino ICT - RAMs at D2 E2 not working
  • replace RAMs
• Still watch-dogging and little else

[*]Remove all ROMs

• DE1 ROM had bent pin
• All ROMs validate
• Realised ROMs DE1 and C1 were switched!

[*]Beep codes - 2114s at M4 and N4 dead

• Replaced and game plays blind!

[*]Pin 1 of L6 put back - watch-dogging

• C8 prom replaced - test grid shows! It's collapsed - see pic below the PCB.

[*]Taken out of test mode and ellipses show in play

• Usually this is an issue in the analogue vec-section
• Systematically socket TL081 and TL082s until issue found (dumb fix but easy)

[*]Checked all the usual suspect ICs and traces with the oscilloscope and saw nothing wrong. Piggy-backing also did not help. Initially I got the Signature Analyser out as I was stuck and I'd never used it before. Was pretty useless at this stage as all signatures verified and it actually only exercising the logic section and I knew that was working fine. It was fun anyway!

• Whipped out the IC Comparator and it worked like a dream!
• Faulty output on LS191 counter at F9
• Test grid fine and game plays!

[*]Sound section now.

• Thump sound is stunted
• Saucer shoot doesn't fade away as it should
• Both issues turned out to be the respective transistors at M8 and N8
• Game works and sounds great!

[*]Fit reversible 6116 mod on request (not shown) to replace those pesky 2114s[/list type=decimal]

Collapsed grid:

Fixed!

 

[Hurray Banana]

Great fixing phil

 

[cparsonsuk]

Awesome work Phil, I've enjoyed getting the updates on this during the month of September as you've gone over the board fixing everything wrong... I hope you've "enjoyed" it too even though the Signature Analyser wasn't useful this time.

Maybe a name change to PhilAsteroids4life ?

 

[Mr20to5]

This is just brilliant. There was certainly a lot to go at on Chris' board. I'm hoping mine may not need quite so much......