Asteroids Deluxe Playing Blind - Not Monitor

64B1T

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Got an Asteroids Deluxe in the workshop I'm very slowly working on. When it arrived, it was stone dead.

After fixing the power supply, the board made sad ram noises and ended up needing a few RAM chips replaced, and then it was playing blind just fine, so I thought all was well in the world.

However, after I fixed the monitor (powered here by Arcade Jason's Vector TPG by the way, which is awesome) I noted that there was actually zero deflection coming out of that board at all, on X or Y.

Didn't have much luck searching forums, as all the hits for "Asteroids Deluxe Playing Blind" yield either monitor problems or purposefully disabling the VG. It's not the voltage regulators on the output either, and the board seems to be properly getting the 36VAC, so I'm not sure off the top of my head what's happening here.

Any pro-tips would be appreciated, otherwise I'll update when I figure it out.

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Got an Asteroids Deluxe in the workshop I'm very slowly working on. When it arrived, it was stone dead.

After fixing the power supply, the board made sad ram noises and ended up needing a few RAM chips replaced, and then it was playing blind just fine, so I thought all was well in the world.

However, after I fixed the monitor (powered here by Arcade Jason's Vector TPG by the way, which is awesome) I noted that there was actually zero deflection coming out of that board at all, on X or Y.

Didn't have much luck searching forums, as all the hits for "Asteroids Deluxe Playing Blind" yield either monitor problems or purposefully disabling the VG. It's not the voltage regulators on the output either, and the board seems to be properly getting the 36VAC, so I'm not sure off the top of my head what's happening here.

Any pro-tips would be appreciated, otherwise I'll update when I figure it out.

View attachment 857270
it's not an issue I've needed to fix before so I don't know for certain what to check, but Chad just fixed an Asteroids that had XY output but was wrong and it was the +15V that was bad. there should be test points for +/-15V, I would make sure those work. I thought the 36V was only for EAROM, are those other voltages derived from that?
 
+15 reads as +14.7 measured at C103
-15 reads as -15.3 measured at C74
+5 DAC reads at 5.02 measured at C85

So I think those are all well within band.

I thought the 36V was only for EAROM, are those other voltages derived from that?
Yes, they're derived from 36VAC at the rectifier formed by diodes CR7-CR10

XOUT is showing 5.87VDC, 0.01VAC
YOUT is showing -0.0078VDC, 0.01VAC
 
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