Bad Tempest, looking for ideas - with video!

SteveJ

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Gentlemen --

Bought a broken tempest, here's what it looks like (top of machine is to the left):

http://www.youtube.com/watch?v=m88FdOCF6RE


The good stuff starts around 20 seconds in: you'll see some vector garbage, followed by a bright spot, then the spotkiller kicks in, turning off the display. Then repeats.

- Monitor is known good (just put it in)
- 5VDC and 22VDC at 5.2 and 24.8, respectively
- Self Test shows blank screen, 1p & 2p lights solid, SLAM switch changes screens, audio good

Any ideas? I'll offer a reward to the first post with the correct diagnosis ;)
 
Reflow your interconnect header pins first.

Looks like you have a bad connection, or bad 2901(s) on you aux
 
Reflow your interconnect header pins first.

Looks like you have a bad connection, or bad 2901(s) on you aux

Ok, so here's what I've done so far:

1) reflowed interconnect pins on both boards, installed new interconnect cable (bought from elektronforge)

2) replaced all original 40-pin sockets with new ones (ALUs, POKEYs, 6502)
3) installed new POKEYs and ALUs (from arcadechips)

(yes, I'm not troubleshooting, I'm shotgunning - but I had the parts so I went for it)

I have a scope and logic probe... are there any good manuals for troubleshooting (that doesn't involve a CAT box?)

Could it be the DACs or Analog Switch?

Oh, forgot to add: Plays Blind.
 
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Multiple issues. If it's not even posting the self test or giving tones then you need to start from the begining. Disable the watchdog and let us know what happens.
 
Whoops. I should also mention that you should flip it to the self text and then cycle the power. See if you get tones then.
 
Ok. I'm an idiot. Didn't see the last bit about it playing blind. Sorry. Yes. Could be the DACs or the MC1495s. Try putting the logic probe on them and see what you get.
 
You can get your scope out, and start checking the X and Y outputs, working backwards to see where the problem is. There are so many things in the video out section that could cause that problem.

So from what I've read, and as I understand it.

Test mode did appear to work and you got beeps between screens.
Game mode wouldn't play but you got garbage out.
Replaced Bit slicers on Aux, reflowed header pins, and replaced cable.
Game now plays but blind

Correct?

Because from the video it looks like you did at first have something coming out, but that could just be garbage because it wasn't running correctly.

Set you scope to 5v/Div and 5ms and see what you get on the x, and then the y output as a wave form.

Your x out should look something like this.

TEK00001.jpg


and your y out should look something like this.
TEK00002.jpg
 
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