Re: [ukvac] TECH: Asteroids - LONG
>From: "Andy Welburn" <warlords@ntlworld.com>
>i had a very similar problem to you when fixing Jim Watt's Asteroids deluxe
>board.......
Anyone know of a supplier of AD561s? Alternatively, does anyone on the list
have one or two they could sell me?
Thanks to everyone who provided advice on fixing my Asteroids PCB with it's
'postage stamp sized display'. It's now 95% fixed with just one small
problem remaining. I now get a full sized display, that is perfect except
for a small compressed area in the horizontal axis. Moving from left to
right across the display the first inch of the display is fine then, the
next inch is compressed, where about three inches of display get compressed
into one. The rest of the display is fine. As objects move horizontally
they get squashed as they move across this area. The problem is only in the
X-axis, and exits straight after the first level of amplification in the
output circuit (C12 - TL082). I've tried replacing the TL082, but the
problem persists. I suspect the AD561 in the X-axis circuit is at fault.
Only problem is I have no spares and can't seem to locate any from the usual
places. If you've seen this problem before and it wasn't the AD-converter
then please let me know....
For those who are interested in the cause of the postage stamp display……..it
was caused by an out of tolerance resistor at R143. Is should be 100K, but
was reading 150K. This resistor is in the inverter circuit that flips the
display 180' for P2 in cocktail games. The inverter circuit should feed
-8.2v to pin 13 and +8.2v to pin 12 of the 4016B ‘switches’ in upright mode.
During a 2P cocktail game +8.2v go to pin 13 and -8.2v go to pin 12,
causing the switches in the 4016B to feed a different (inverted) signal to
the monitor. However, due to the faulty R143 -8.2v was being fed to both
pins 13 & 12, causing both normal and inverted signals to be passed through
to the monitor. The postage stamp size image must have been what was left
of the signal after the inverted and non-inverted signals had cancelled each
other out. The fact that there was any signal at all must have been due to
difference in the tolerances of the components in the two circuits.
I spent hours and hours fiddling around with this, to find it was a poxy
little resistor at fault! The task wasn't helped by the fact that both the
reference board (bootleg asteroids) and the schematics I was using had no
trace of the cocktail invertion circuitry!!! The ones on Spies do, but they
are almost unreadable in parts. Anyway, nearly there.....
Regards,
Steve
_________________________________________________________________
Chat with friends online, try MSN Messenger: http://messenger.msn.com
>From: "Andy Welburn" <warlords@ntlworld.com>
>i had a very similar problem to you when fixing Jim Watt's Asteroids deluxe
>board.......
Anyone know of a supplier of AD561s? Alternatively, does anyone on the list
have one or two they could sell me?
Thanks to everyone who provided advice on fixing my Asteroids PCB with it's
'postage stamp sized display'. It's now 95% fixed with just one small
problem remaining. I now get a full sized display, that is perfect except
for a small compressed area in the horizontal axis. Moving from left to
right across the display the first inch of the display is fine then, the
next inch is compressed, where about three inches of display get compressed
into one. The rest of the display is fine. As objects move horizontally
they get squashed as they move across this area. The problem is only in the
X-axis, and exits straight after the first level of amplification in the
output circuit (C12 - TL082). I've tried replacing the TL082, but the
problem persists. I suspect the AD561 in the X-axis circuit is at fault.
Only problem is I have no spares and can't seem to locate any from the usual
places. If you've seen this problem before and it wasn't the AD-converter
then please let me know....
For those who are interested in the cause of the postage stamp display……..it
was caused by an out of tolerance resistor at R143. Is should be 100K, but
was reading 150K. This resistor is in the inverter circuit that flips the
display 180' for P2 in cocktail games. The inverter circuit should feed
-8.2v to pin 13 and +8.2v to pin 12 of the 4016B ‘switches’ in upright mode.
During a 2P cocktail game +8.2v go to pin 13 and -8.2v go to pin 12,
causing the switches in the 4016B to feed a different (inverted) signal to
the monitor. However, due to the faulty R143 -8.2v was being fed to both
pins 13 & 12, causing both normal and inverted signals to be passed through
to the monitor. The postage stamp size image must have been what was left
of the signal after the inverted and non-inverted signals had cancelled each
other out. The fact that there was any signal at all must have been due to
difference in the tolerances of the components in the two circuits.
I spent hours and hours fiddling around with this, to find it was a poxy
little resistor at fault! The task wasn't helped by the fact that both the
reference board (bootleg asteroids) and the schematics I was using had no
trace of the cocktail invertion circuitry!!! The ones on Spies do, but they
are almost unreadable in parts. Anyway, nearly there.....
Regards,
Steve
_________________________________________________________________
Chat with friends online, try MSN Messenger: http://messenger.msn.com