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GameDude
18th November 2007, 09:59 PM
Started of by making a basic harness, nothing more than +5 +12 -5 and GND and the RGB and sync, This board needs all voltages for the notorious 4116 memory.
Powered on to a rather pathetic red screen, I noted that the screen also had dots that slowly disappeared as the PCB warmed up..

Started by checking the clock and since there was no crystal I installed one with no real change to the fault except now the watchdog resets.

Checked a few of the roms and repaired badly corroded legs... still no change although the bad rom connections would not help so it was a step forward.

Since the ram had a high chance of being bad based on the observation of the screen when first turned on I desoldered and socketed all 4116 ram and inserted known good memory as I will test the 4116 later when the rest is fixed.

Tried again and now get a nice solid red stripped screen no dots....

Decided to stick it on the fluke to see what was happening, system bus test OK but RAM and ROM test returned instant failures.
Since the bus test was OK I moved onto the memory address decoders and probed around the associated IC's.
The 7442 at N2 was not outputing on any output so I piggybacked a 74LS42 and BINGO! the MISSILE COMMAND attract screen came up :D

OK now desolderd the bad 7442 and replaced I checked the 4116 ram that was originally in the PCb and found one was bad.

Now with a working PCB I wired up the rest of the harness and attached a 2.5inch trackball, since there is no onboard amp for the audio I decided to make an audio probe.
Basically the audio probe is nothing more than a set of cheap speakers and a set of probes with interchangeable clips.
Hooked all the rest and had a game:D:D:D

I have never played Missile Command before except on the 2600 and it is a bit different... much more fun with a trackball and three buttons to fire missiles......

Parts Needed to Repair:
1 x 74LS42
1 x 10Mhz Crystal
8 x 16pin dual wipe sockets
1 x 4116 memory IC

GEMINI
18th November 2007, 10:05 PM
good reading

MrQuan
18th November 2007, 10:07 PM
Nice one :) Save another PCB! :D

When you talk of the Fluke, do you mean a Fluke oscilloscope?

GameDude
18th November 2007, 10:10 PM
Some more pictures....

GameDude
18th November 2007, 10:16 PM
Nice one :) Save another PCB! :D

When you talk of the Fluke, do you mean a Fluke oscilloscope?

No.... Check this thread..
http://www.aussiearcade.com/showthread.php?t=7406

Third picture down its that massive calculator looking thing... I connect it via a serial port to a PC and run software called FIDE which is ultra handy as it allows scripts to be run easily.
The scripts come from ...
http://tech.quarterarcade.com/Tech/CodeGenerator/
For the code generator and...
http://tech.quarterarcade.com/tech/
This link for the Virtual Machine code used in the generated scripts...

Beats manually typing in address codes into the fluke... :p

xygt
18th November 2007, 11:15 PM
Ta for the Fluke info, been meaning to ask you about it.
Good to see that the Pokey worked ;)

GameDude
19th November 2007, 09:19 AM
Ta for the Fluke info, been meaning to ask you about it.
Good to see that the Pokey worked ;)

Yep it worked :) a bad POKEY can cause problems on these PCB so needed a worker to be sure there were no problems in that area.