Re: Amplifone jitters

Last night I had a few moments so I started to do a little
troubleshooting. Hooking up the scope proved that the video output is
clean, therefore it's the monitor that has some problem.

I actually noticed two different problems, the jitter is one, but the
other is that now all of a sudden, those fireball explosions which are
bright, cause the screen to expand and contract about an inch. It's
just like what some people report when the Death Star explodes, however,
my system has never exhibited this behavior until now, and it happens
not just on the Death Star explosion, but on any explosion that's
bright.

Didn't someone say that the expanding and contracting occured because
the 24 volt regulators couldn't supply enough current at that moment?
If so, could this effect be eliminated by having a more robust +/-
24volt supply replace those regulators? Could the LV2000, for instance
be used instead to supply a nice regulated +/- 24 volts?

With respect to the loose wire issue, I'll take a look tonight. I did
check the ground wires on the power supply, and they were still firmly
in place.

The good news is that I can swap in any component in the game with
others, so that will at least tell me which assembly is at fault if it
comes to that.

Anders Knudsen wrote:
>
> I seem to remember that Jeff Hendrix had this similar problem with an
> ampliphone. It turned out that some wire (might have been the HV wire) off
> the transformer was loose. I am speaking from faded memory here though.
> Perhaps Jeff can remember. If you could stick a scope in XY mode off the
> PCB outputs and they are "clean", then your jitter problem is the monitor.
>
> -Anders.
>

Zonn wrote:

>Just out of curiosity, do you still have the metal cage around the HV? Not
>having the cage will cause the displays to jitter.

I didn't realize there was a metal cage around the Amplifone's HV board?
Is this a typo?

I guess the absence of mine is not helping things any. However, I do
own the metal cages for the Wells Gardner monitors, but I don't use
them, but their absence has not had any negative effect (jitter wise at
least) on the video quality. The Wells Gardners seem to be rock steady
as long as the ground wires are solid, and the caps in the LV supply are
not leaky. At least, that has been my experience with my Tempest which
once suffered from jitter problems until I checked these two things. I
actually had the problem in two different Tempests, the ground wires
fixed one, and the LV cap replacement fixed the other beautifully.

If anyone has any other leads to follow up, that would be great! If
someone could comment on the utility of replacing those 24v regulators
with a better supply, that would be good too.

Thanks!
Joel-
Received on Wed Jun 24 09:30:09 1998