My Asteroids is acting crazy

action53

Well-known member
Joined
May 17, 2016
Messages
1,764
Reaction score
91
Location
West Columbia, South Carolina
Ugh, I knew someone was going to misbehave right before we had people over for Christmas




The +5 is exactly 5.0 at the test points on the board and 5.4 at the test points on the ar2, I replaced the big blue a few months ago. The coin counter randomly advances itself and it does it when I hit player 2 start. On the test screen I get two low tones that sound exactly alike and that's it, nothing on the screen.

It was even crazier before I started filming, both players had tons of extra ships drawn, asteroids were stuck together and moving in strange ways, repeatedly exploding, etc...
 
Test mode is the clue. Likely a bad RAM. See the manual for deciphering the test tones. Your sound circuits are getting stuck on, which is why you're hearing the sounds in attract, and if the game was otherwise working normally, it might just be a bad switch IC in the sound circuits. But the fact that it's resetting, and giving the tones in test mode suggests it's actually something else, and most likely RAM or bus related.

Sometimes the tones can get messed up if the test isn't running or completing fully, and it can be hard to tell high vs low tones, or if the low tone is even happening, as it can be missing in some cases. You'd need to start replacing the RAM chips (starting with the first ones indicated by the tones), if you don't have the ability to debug further.

If you are looking to send it out for repair, feel free to PM me.
 
The guy I got it from offered to repair it for free. I'm going to try reseating everything, I think I have some ram kicking around somewhere too. Maybe I'll go deeper if Santa got me a logic probe
 
Normally you should hear a series of tones, followed by one much lower tone. In your case both of the tones are the same, which isn't exactly clear.

It might jut not be shifting the pitch of the second tone lower (in the case that E2 is bad), or maybe it's resetting or otherwise not completing the self-test, in which case it might just be omitting the last tone(s), and maybe it's one of the higher ones that are bad (M4, R4, N4, or P4).

I'd lean toward it being the latter case, and would try replacing M4 first. Without the tools required to test the RAM separately, all you can do is start socketing and replacing them one by one.

The good news is that once they are socketed, they will be much easier to replace should they go bad in the future, so it's not exactly time wasted. However you also increase the chances of introducing new problems with every chip you replace, so you want to be very careful when replacing them, not to pull any traces or cause shorts under the sockets.

Honestly, it's fairly tricky to remove those chips without a desoldering gun (which is what I use), and you only want to do it manually if you are very comfortable with removing chips with just a sucker.
 
You're right, I'm not going to chance making it worse. Could I piggyback a good ram on top of the suspect bad ones or does that not work?

that sometimes works (i.e. on a WL PCB) but might not work here ... but try it and see ... (experimentation is good)
 
Last edited:
I have 2114 ram chips at L2 M2 M4 N4 P4 and R4

If I piggy back one on M2 I get a high tone then a low tone in test mode

I can't find D2 or E2 on the board

Edit:

With a ram piggy backed on just L2 I can actually start and play a game but the coin counter goes nuts and the asteroids are all jumpy and randomly reappear after exploding and the explosions stay on screen a while. Like this in test mode I get one low tone. Attract mode looks somewhat normal
 

Attachments

  • 20171220_225934.jpg
    20171220_225934.jpg
    648.3 KB · Views: 7
  • 20171220_230129.jpg
    20171220_230129.jpg
    585.5 KB · Views: 8
Last edited:
There are at least six or seven different revisions of Asteroids PCBs, so the info in the manual needs to be taken loosely, to say the least. You can sort of extrapolate how the locations relate, as they move around slightly between the different versions.

I've never had much luck piggybacking chips myself, but that's just been my experience. Others here may tell you otherwise, but I think you need to just start replacing RAM, or send it out to someone.
 
D2 is L2 and E2 is M2 on my board. I piggy backed a good ram onto L2 and I got a high tone then a low tone in test mode instead of the two low tones. I moved the piggyback to M2 and two low tones again. I tried to desolder M2, realized I probably shouldn't try and resoldered it back in before I lifted any traces. I plugged the board in with no piggyback and the original problem was still present. I piggybacked a ram onto M2 again but accidentally crossed some legs or something and when I fired it up it was resetting like mad and the coin counter sounded like a machine gun. I powered down, piggybacked the ram correctly and fired it up and now it works fine.

I'll tell you one thing though, the first thing I'm getting come "adult Christmas" is a nice hakko
 
I'll tell you one thing though, the first thing I'm getting come "adult Christmas" is a nice hakko

Don't fool yourself ... even with a nice hakko desoldering gun (and/or soldering iron), you can do major damage to the PCB. Soldering/DeSoldering is a skill. Just because you have the equipment does not mean you'll magically become adept at any skill.

"Practice makes Perfect".
(Also, my advise, would be to take your time, be patient, and take care when working on any >30yr old PCB) :)
 
Back
Top Bottom