Asteroids issue

Tufnel

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every once in a while on my asteroids everything on the screen will disappear except for the ship and any bullets I fire. The UFO seems to stay also.

Everything else (score, asteroids, other text etc) just goes away for a few seconds and comes back. Makes playing the game even more challenging since you have no idea where anything is for a few seconds at random

Before I get too far into it I figured i would ask first if anyone has seen this before since it seems like a pretty specific behavior.
 
if you need cap kits i have them all in stock for any of the models and if you not sure which one you have pm me and send me a picture and i will be glad to help.
 
every once in a while on my asteroids everything on the screen will disappear except for the ship and any bullets I fire. The UFO seems to stay also.

Everything else (score, asteroids, other text etc) just goes away for a few seconds and comes back. Makes playing the game even more challenging since you have no idea where anything is for a few seconds at random

Before I get too far into it I figured i would ask first if anyone has seen this before since it seems like a pretty specific behavior.

Replace the caps in the spotkiller circuit.
 
My Asteroids was doing something very similar (until it stopped turning on at all).

Are these monitor/cap suggestions actually verified?

To me it very much feels like a board issue - the software creates a list of vectors which the AVG hardware turns into signals to drive the monitor. Items disappearing very consistently feels to me like the list is being truncated (eg, RAM or TTL counter). Think of it like the ship and UFO are at the start of the vector list, then the asteroids and text at the end.

I don't see how the monitor could ever fail in such a way that these elements would be so consistently dropped out without affecting others.

Anyway, I'll debug mine over Christmas, luckily I have an Asteroids Deluxe too so can swap boards/monitors - should be immediately obvious if the problem follows the monitor or the board.
 
My Asteroids was doing something very similar (until it stopped turning on at all).

Are these monitor/cap suggestions actually verified?

To me it very much feels like a board issue - the software creates a list of vectors which the AVG hardware turns into signals to drive the monitor. Items disappearing very consistently feels to me like the list is being truncated (eg, RAM or TTL counter). Think of it like the ship and UFO are at the start of the vector list, then the asteroids and text at the end.

I don't see how the monitor could ever fail in such a way that these elements would be so consistently dropped out without affecting others.

Anyway, I'll debug mine over Christmas, luckily I have an Asteroids Deluxe too so can swap boards/monitors - should be immediately obvious if the problem follows the monitor or the board.

Interesting you should say that.. I was thinking a board issue originally.

One time when it acted up I just tried to make sure everything on the board was seated ok and it seemed to work fine after... may have just been a coincidence though.

its pretty random.. things drop out and then come back a few seconds later. Once in a while it doesnt happen at all.

self test looks ok to me
 
The reason some objects remain visible and others disappear is because they are drawn at different intensities. That's the Z channel which is of course generated by the PCB but then amplified by the monitor. It then has to run the gauntlet of the spot killer which is sampling X and Y to make sure the beam is moving. If there's not sufficient XY activity (or bad caps aren't allowing it to be detected) then the Z signal gets whacked (or partly whacked in your case).

So do a cap kit on the monitor deflection board (and reflow its headers while you have it out).
 
It would help if you can tell us which monitor it has, as Asteroids can have a couple of different ones.

If it's a G05-802 or 19v2000, see this thread. In particular, read posts #1 and #33.

http://forums.arcade-museum.com/showthread.php?t=356350


Earlier Asteroids cabs came with a G05-801, which is different, and I can't say that it has the same issue. (I suspect it doesn't, as the layout is different, and it doesn't have the large resistors that are responsible for the issue above.)

Google image search the monitors to determine which one you have.
 
Slight thread hi-jack but as we're here..

Got my game running again after replacing sockets and fixing a bunch of really corroded ROM pins. Played pretty good for 20 minutes but then the stuff disappearing problem came back. Monitor cap kit sounds a good idea - I don't need to discharge the CRT when removing the deflection board right? I've never discharged a vector before and I believe I need to get 1M ohm in line to do this without damaging anything?

The bad news is after 20 minutes the screen had expanded a lot (blooming?) - I believe this is the HV diode? (And I'd certainly have to discharge to go near that).

Any recommended suppliers for the diodes?

(Edit - my monitor is the Wells)
 
- You don't need the resistor in line to do the discharging. This has become a myth of sorts, and there is plenty of data out there that says you don't need it.

- Many people (including me) have been getting diodes from this guy (who also has other quantities, see his other listings):

http://www.ebay.com/itm/132021216610

- If you have the Wells Gardner 19v2000, replace Q500 and Q501 with MPSA06's, and do the mod that removes R100 and R101, by replacing them with straight pieces of wire. That will have a good shot at fixing your problem (and won't hurt to do regardless).
 
Capkit (deflection board and HV board) installed and high voltage diode replaced. I _think_ this has fixed my problems 100% so looks like it was the monitor not the board after all.

(Think - as it was an intermittent issue, and I think I saw the ship disappear right after I booted for the first time after replacing parts - but not seen anything since, so maybe I imagined it...).

Monitor looks as good as the day it left the factory now :)
 
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