Re: Tempest lines fading

I'm maybe not up to speed on this one, have you tried the pcb with a
different monitor or vice versa ?

I have come across temperamental blanking Z circuits in G05's and 6100's
before, usually its down to a transistor breaking down under load in the Z
section on the monitor... very hard to spot as the transistors checked good
out of circuit on my meter (fluke 12 that can spot leakage).

I also had a similar problem with a battlezone pcb that would trip the Z
circuit on the G05 infrequently.. I didn't suspect the pcb until i got
another G05 which did the same thing and realised it was the pcb not the
monitor... the battlezone AVG section 'crops' the picture so that it doesn't
display a super widescreen version, and instead makes it 4:3 for the monitor
(yes thats a simplified rendition of what it actually does).. what was
happening in my case was the picture wasn't being cropped, so even though
the game played perfectly, it was displaying the mountains way off the side
of the tube, therefore giving the Z section on the monitor a headache as it
wasn't sure if it should kill the beam or not. This probably doesn't apply
to tempest as there are no conceivably huge landscapes involved....

Maybe that doesn't help, but try shotgunning the Z on the monitor, a handful
of 2n3906's and some MPSA56's i think should do the trick. It just sounds
odd that it would be the same problem on 2 pcbs...

Andy Welburn
www.andys-arcade.com

----- Original Message -----
From: "Joe" <jb@joesarcade.com>
To: <vectorlist@vectorlist.org>
Sent: Tuesday, August 26, 2003 4:02 PM
Subject: VECTOR: Tempest lines fading

> I have two Tempest boards here in which the vectors fade in and out. On
> the one board, I notice it most on the horizontal vectors. They start
> off as a normal width, but will change to about half the width. When
> faded, zeros on the screen look more like ones. Do, a high score of
> 1010101 would look like ||||||||||, but with VERY faint lines connecting
> the tops and bottoms.
>
> I've been concentrating on the DAC-08 area, but I feel I may be chasing
> a red herring here... I know this is not related to the aux board. Any
> suggestions?
>
> Thanks,
> JB
>
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Received on Tue Aug 26 20:05:03 2003