Re: Tempest displays on scope, but not 6100

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 22 23:13:40 2013