Moon Base Cocktail

[int21h]

Hi all,
I recently got hold of a Moon Base game. It powers up fine (as in, the fan runs, and it played the sound that is made when the alien goes across the top of the screen once, havn't been able to get it to make a sound since though). The screen originally didn't come on but I found 2 blown fuses and replaced those. I got the following screen then:

Assuming that it's a blown capacitor, I searched all the boards for one but I didn't see one (could have been one that I missed).

I put a coin in at that screen only for it to change to a blank:

Now when I reset the machine it goes back to that screen.

Can anyone advise me where to go from here?

Many thanks!

 

[forcefulfil]

1-Have you verified all the voltages?

2-Clean and re-seated the roms/socketed chips/edge connector?

 

[int21h]

1-Have you verified all the voltages?

2-Clean and re-seated the roms/socketed chips/edge connector?

Hi there,

Thanks for your reply!

I'v checked a few pins on the transformer (not all) and it's giving out 237 volts. Havn't tried any of the other suggestions though so I will do that tomorrow morning when I have access to it!

I found this image another user put up;

on the left side of his transformer he has wires coming from the top terminals, whereas mine only has the bottom 2 connected to something. I also noticed he has an extra board to the right side of his screen which mine doesn't. (I was told it was working and then stopped, the person who gave it to me wouldn't be the kind of person to remove parts, or know how)

 

[P-Man]

Dont look at the transformer, you need to measure the 5v, 12v and -5v on the game pcb, make sure they are present before doing anything else. I can't give you the info on where to measure this because you have the unusual single layer moon base pcb and i do not know the pinout of that one. you can measure the 5v at the very least over normal TTL chip.

 

[int21h]

Never done the whole multimeter thing before!
It seems to be a NEC/Intel 8080; I can't find a pinout for this on the net.. Do you know which pins I need to test? Also do I do this while the machine is on?

 

[P-Man]

the 8080 is the cpu, leave it be...

the power comes in on the edge connector, put your black lead on the pins on one end, this is likely to be ground, then measure soem of the ticker foil traces, you need to find 5v and 12v at least, possibly -5v.

 

[int21h]

the 8080 is the cpu, leave it be...

the power comes in on the edge connector, put your black lead on the pins on one end, this is likely to be ground, then measure soem of the ticker foil traces, you need to find 5v and 12v at least, possibly -5v.

Sorry for the continuous rookie questions.. No better time to learn I guess! I'm not fully sure what you mean (not up to scratch on PCB terminology); do you mean between points 1 and 2 or 3 and 4; or other?

 

[P-Man]

set multimeter to volts DC

put black lead on 1, then put your red lead to measure the rails as follows:

I have ammended your photo in orange, put the red lead where the orange lines land and get back to us with the results for 2,3,4,5,6..

 

[int21h]

Thanks for that!

The results are:

Pin | Volt

5 | 4.83

4 | 11.88

3 | 4.83

6 | -5.15

 

[P-Man]

and what about 2 ?

So far it looks like your 5v is a bit low, the game probably will run at this level, but you should adjust the 5v level by a trimpot on the PSU, this may be buried under the monitor, so you may have to remove it, adjust it a little bit, re-install then retest.. its often hard to get to, and is definately dangerous to stick your hand in there while its switched to adjust it because of the proximity to the monitor so go careful.

I should add.. if adjusting the 5v level up to 5.05v does not make the game spring to life then you need the pcb fixing...

P-Man2012-03-31 16:08:34

 

[int21h]

Oops I forgot about pin 2!
That's 17.54 volts

I didn't see any switches down there yesterday but I'll check again now and have a look!

 

[P-Man]

its not a switch.... its a power supply...

 

[int21h]

Yeah I meant an adjustment switch on the board under the TV (assuming that one is the PSU)
This board is behind the TV at the bottom

But there's another variable switch on the board connected to the TV I didn't see yesterday, near the back of it

 

[P-Man]

ok, if you can reach this adjustment pot easily, (its not a switch, its a pot - potentiometer, a variable resistor) turn it with a flat blade screwdriver and you should be able to turn the 5v (on measurement point 3) up to 5.05v

Be careful in there.. and dont touch the other pcb that is hooked to the CRT..

that psu isnt as buried as it could be, so thats a bonus.

P-Man2012-03-31 16:31:37

 

[int21h]

I'v turned it up to 4.98 volts (still a white screen) does it need to be exactly 5.05v?

 

[P-Man]

nope, 4.98 is close enough if thats as far as it goes. If its not firing up you will need the board repairing...

 

[int21h]

Hmm. What would be the best way for me to diagnose what's wrong with it?
The odd thing is, the first time I turned it on, after a minute or so it played one of the sounds. When I got the screen working it was fuzzy (like a blown cap, see above screen). There's a cap on one of the boards with white leakage but it doesn't look damaged so I assumed that was a glue?

If it is kaput where do you suggest I get it fixed?

 

[P-Man]

No offense, but with your level of skills, it is not going to be possible for you to troubleshoot this further unless you want to teach yourself electronics, i'm afraid i can't teach you or step you through it...

The sound you heard is completely normal, the sounds are pre-formed analogue circuits that are simply triggered by the game when it wants to play them. Often when you turn on space invader games like this you will hear some of the sounds play.

I do repair pcbs, but i have a lot of other work on at the moment and i'm not taking on any repairs until maybe august/september.

 

[int21h]

That's fair enough! Thanks for your help
I'll get an electronic engineer to call down tomorrow.

 

[int21h]

I'v called an engineer and he'll come down tomorrow
Just out of curiosity, how does the .. screen data (?) get from the game PCB to the screen PCB? There only seems to be a power cord going into the screen PCB