Re: Tempest displays on scope, but not 6100

On 06/22/2013 4:02 PM, IAN EURE 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.
>

Do you hear the 'chatter' from the yoke? If you do, then chances are
something is wrong with either the HV or something with the cathode
circuit. You do realize that you can hook the 'scope to the picture tube
cathode to see what is going into the tube...

I'm assuming the neck has a red glow (filament)...

John :-#)#

-- 
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
                  www.flippers.com
"Old pinballers never die, they just flip out"
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