SOLVED: More Cinematronics/Hantex stuff. No chatter, dot on screen.

texasmame

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I had no pic but chatter. Then. . .

Something went haywire while testing, taking out the 7406 (blew the top right off it) on the chassis. Socketed and replaced but now I get no pic AND no chatter; before I did have chatter but no pic. This is with two different boardsets, one known good and both do the LED on then off when booted.

Replaced the four 47ohm resistors as two of them were pretty crispy. Reflowed EVERYTHING on the chassis and replaced the four heat sink transistors.

All I get now is a dot in the upper right corner of the screen. I can adjust the intensity of it with the brightness control, so guess I at least have HV. :)

The three voltages are correct from those three voltage regulators on the chassis (5, 15, -15).

So, besides the 7406, what else was probably destroyed with the surge (no visible indicators of any other problems).

Lastly, breaker 2 trips after about 30 seconds, followed almost immediately by breaker 1.
 
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UPDATE: Replaced the LF13331 (outputs all dead on original one) and now I get chatter and a pic but it is this pic. It's supposed to be Armor Attack. The lines all move with each "group" moving independently of one another (you can even tell when the chopper comes out but it's also just a jumble of lines that move as one). The only thing that looks normal on the screen are the shots.

No more breaker tripping.

My "known good" boardset produces this picture and the one that came with the game also produces chatter now but no pic at all.

Suggestions from here?
 

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UPDATE: DACs replaced, no change. TL081s replaced, no change. Resistors on underside of chassis for DACs check out as good (820ohm).

I now have two boardsets that produce the same pic, so leaning heavily towards a chassis issue and not boardset issue.

Now with less-sucky pic attached!
 

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FINAL UPDATE: Solved!

After getting both boardsets producing a pic, I went back and started to double-check a few things. Swapped out the 7406 on the chassis - no change. Swapped out the LF13331 on the chassis - BINGO!

Apparently, one of the LF13331 I got from Mouser was bad (or went bad) after putting it in. It brought back the chatter and, thus, the pic but apparently something in it was off just enough to make the pic look all fucky.

Thanks to

i86time

for some guidance on this one. He's also an excellent choice for ship-out Cinematronics repair, BTW!
 

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