PCB Repair Logs Missile Command

Missile Command

Missile Command

PCB Image	Missile Command PCB
Pin Out	Reserved

Repairer: Prof
Forum Thread: Missile Command PCB Repair

OK, won a Missile Command off ebay, description said parts pcb, but anyway.

OK Recieved the pcb, quick look, missing the crystal 3 eproms 2 eprom sockets and the cpu.

Burnt 3 new roms and installed 2 sockets, put a good cpu and crystal in, changed all the 4116 rams (I bought a few nos off ebay) Fired it up, yellow screen.

OK, time to have a better look, ended up straighting all the pins on the back of the pcb that where touching, tried again, now a white screen and reseting, better.

Try the test mode, goes into it, give a rom 2 error sometimes. Verfy the rom, nothing, resolder the socket, nothing.

Check the rom addressing ciruit, found a bad 74ls42 at N2 and a bad 74ls153 at F3. Changed with new chips, voila, working Missile Command But, seems to have the yello background missing, odd, will get the schematics and have a look.

Okay, found the problem with the missing yellow mountains, bad 7474 at A7, replaced with a good one and now running 100%

Repairer: GameDude
Forum Thread: Missile Command PCB Repair

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.

OK now desoldered 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

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


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