Re: Tempest displays on scope, but not 6100

I got back to this today, and I'm still completely stumped. I checked the RGB outputs, and they seem fine. I compared the X and Y sections individually on the scope to a working board, and everything is within range. On the RGB outputs, I see them turning off and on like they should — nothing stuck there. I also compared those to a working boardset, and they seem fine.

I checked the X and Y grounds, and they are fine. It looks like there's an error in the schematics, as the video return line is marked as pin M of the AVG edge connector, but this hooks to the collector of Q7, which is for the middle coin mech. Either way, the ground pins on the 6100 connector have continuity to the ground plane on the PCB, and the ground is correctly hooked to Q10.

My understanding is that the SK operates by shutting off the beam current, no matter what causes it to activate — which is to say, if deflection is present, it is unaffected by the spotkiller. This is where I'm hung up: I /have/ deflection on the scope, but even when I turn up the brightness on the 6100, I have no deflection.

Any other ideas?

On Jun 22, 2013, at 8:13 PM, Rodger Boots <rlboots2@gmail.com> wrote:

> If X is good and Y is good make sure ground is also good. A long shot.
>
> Well the voltage output on x and y could be out of range for the monitor. So I would take the scope out of xy mode and measure the voltage output of the x and y. It's probably good from reading your write up.
>
> I can't recall if the color output circuit would cause this problem, typically I've only seen 1 color go bad before, but maybe you are missing all three?
>
> I would most likely suspect the z outputs from Data shifter H7 Try checking those outputs, and reseat the 2 VG Eproms JIC.
>
> Kevin
>
>
>
> On Sat, Jun 22, 2013 at 6:02 PM, IAN EURE <ieure@mac.com> wrote:
> I have this Tempest PCB I've been working through. I have it displaying a self-test screen indicating some errors that need work, but I can only get the screen to come up on a scope. Because I have no Z channel and only have 10x probes, I can't read the error codes on the scope. When I hook the game to a K6100, I just get a spotkiller.
>
> Has anyone seen this before?
>
> I know it's not the monitor, because I'm testing in a working cabinet. I thought it might be the PCB adjustments, but I used the scope to calibrate them to the same levels as another PCB, which does display in this cabinet. I turned off & disconnected the scope, in case that was interfering with anything; no change. I'm hooking the scope to the X/Y out test loops on the board. I thought there might be a broken trace between there and the edge connector, but I checked and there is continuity. I turned the screen control up on the 6100 to bypass the spotkiller, and all I have is a dot in the center; no deflection at all, despite seeing a signal on the scope.
>
> What am I missing here?
>
> Background: Got the board resetting in game mode and blind in test. Cleaned & reseated ROMs, and got it playing blind as well. But it went back to resetting a day later, which indicates dodgy ROM sockets. I'd prefer not to replace all 10, so I decided to get self-test going so it would tell me which were faulty. Replacing the TL082s got me a box in self-test with no text, and swapping the ROM @N/P3 got me a reasonable looking test screen. But I can only see it on the scope.
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Received on Sat Jun 29 17:07:00 2013