Working on an Asteroids PCB (-04 version) on my bench.
Got two vector rams replaced and now the game boots and plays fine but I have graphic issues, see video.
I think the issue is on the "X" side?? and I have two new DACs and two new 4016B's on order. I have switched the existing chips with each other but the graphic doesn't change (to the "Y" side) so those may not be the issue.
I did replace all four Op Amps and no change.
My 36vAC is supplied by an Atari brick and tests fine on the board but my rendered 22vDC is low, around 12v. That is obviously causing some voltage issues but not sure if a VR is bad or a downstream component is pulling it down. And not sure if the voltage issues is causing bad graphics, or the bad graphics (component) is causing bad voltages.
The +5v (7805) and -15 (7915) outputs both test fine, but +15 (7815) is running more around 10.7 (due to low 22v rail). In suit, the -8.2v is fine, but +8.2v is low (~6.7v). The +12v (7812) is also at 10.7 (due to low 22v rail).
So, I first focused on the VR's.
Pulling 7815 output leg out of circuit does not resolve the issue.
Pulling 7815 input leg out of circuit does not resolve the issue.
But then, pulling 7812 output leg out of circuit (with 7815 input and output leg still pulled out) and I get 22vDC on that input rail.
So, I figure it was the 7812 or downstream component on that circuit and I put 7815 input leg back in circuit (with 7812 output leg still out) and 22v rail drops to 18v. Then, I put the 7815 output leg back in circuit too (with 7812 output leg still pulled) and 22v rail goes back down to 7v. FML
So, it's clearly not the 7812… or just the 7812, and doesn't appear to be the 7815, or only the 7815. So, I changed out the 7812 but no change. I don't have a new 7815.
Then I wondered if somehow the current on the 36vAC was too low and with everything pulling on it that was causing the 22v to drop, and so I swapped in another Atari brick and same issue. But I will admit my jumper leads are not a large gauge.
So, when parts arrive I'll swap in the new 7815, both new 4016B's, and both new DAC's, but if that doesn't improve it what should I check next?
Hope that all made sense.
Got two vector rams replaced and now the game boots and plays fine but I have graphic issues, see video.
I think the issue is on the "X" side?? and I have two new DACs and two new 4016B's on order. I have switched the existing chips with each other but the graphic doesn't change (to the "Y" side) so those may not be the issue.
I did replace all four Op Amps and no change.
My 36vAC is supplied by an Atari brick and tests fine on the board but my rendered 22vDC is low, around 12v. That is obviously causing some voltage issues but not sure if a VR is bad or a downstream component is pulling it down. And not sure if the voltage issues is causing bad graphics, or the bad graphics (component) is causing bad voltages.
The +5v (7805) and -15 (7915) outputs both test fine, but +15 (7815) is running more around 10.7 (due to low 22v rail). In suit, the -8.2v is fine, but +8.2v is low (~6.7v). The +12v (7812) is also at 10.7 (due to low 22v rail).
So, I first focused on the VR's.
Pulling 7815 output leg out of circuit does not resolve the issue.
Pulling 7815 input leg out of circuit does not resolve the issue.
But then, pulling 7812 output leg out of circuit (with 7815 input and output leg still pulled out) and I get 22vDC on that input rail.
So, I figure it was the 7812 or downstream component on that circuit and I put 7815 input leg back in circuit (with 7812 output leg still out) and 22v rail drops to 18v. Then, I put the 7815 output leg back in circuit too (with 7812 output leg still pulled) and 22v rail goes back down to 7v. FML
So, it's clearly not the 7812… or just the 7812, and doesn't appear to be the 7815, or only the 7815. So, I changed out the 7812 but no change. I don't have a new 7815.
Then I wondered if somehow the current on the 36vAC was too low and with everything pulling on it that was causing the 22v to drop, and so I swapped in another Atari brick and same issue. But I will admit my jumper leads are not a large gauge.
So, when parts arrive I'll swap in the new 7815, both new 4016B's, and both new DAC's, but if that doesn't improve it what should I check next?
Hope that all made sense.
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