Asteroids pulsing

[andyman]

Vectors are doing my head in, help !!

First vector board I've ever looked at, with a view to repairing so after looking at it for 30 mins, found a missing 12mhz crystal and 2 data lines from the 2114s broken, took a crystal off a Williams board, repaired the traces, replaced and socketed the 2114s and we have game

Only problem is, the screen kind of pulses at the same speed as the flashing start buttons and the game runs at about twice the speed of normal and I haven't got that far yet.

This is the second board I've almost got fully working, the other ones text and other bits are up at wrong angles and I cannot get that any further.

Any help on where to look would be most appreciated

Andy.

 

[Equites]

Andy, you sure the PCB has not had the speed hack done on it?

The pulsing sounds like a bad Z circuit?

 

[andyman]

Deffo no speed hack as this requires hard wiring and there is none. What could be causing the Z circuit to pulse the screen then, I have no clue, schems have been out so many times, I've crumpled the edge of the PDF

Andy.

 

[andyman]

Seems to get more jumpy with lots of rocks on screen, doesn't do it on test or on high score entry though.

Andy.

 

[Equites]

Do you have a scope? Have you checked the Z Output?

Also check that edge connector.Equites2011-10-14 12:20:10

 

[DanP]

Also check the grounds. Is there any resistance between the AR1 and the PCB and monitor ground points?

Dan

 

[andyman]

Ok, video problem solved, turned out to be a bad TL082 on the Y output

Still too fast though

First proper game of Asteroids in 20+ years

Andy.

 

[guddler]

Some basic info first!

Is this a real vector monitor, a scope, or what?

As for the speed up, the hack doesn't necessarily require wires. Is pin 4 of C5* (a 74LS161) intact? If it's lifted or cut and connected instead to 5v then that'll make it run at twice the speed. If it doesn't appear to be hacked in any way then remove C5* and check it.

*IC locations may vary depending on board revision.

 

[guddler]

I'm sure there's another way of achieving the speed increase too but I can't remember off hand.

 

[andyman]

Monitor is a G05

Ok will go check C5*, board revision is 06 but written in black marker ?

Only just got into Atari so bear with me

Andy.

 

[andyman]

C5 missing pins 3 & 4, nicely done, almost invisible

Cheers guys, all happy now

Andy.

 

[guddler]

Love it when things come together like that