Re: Amplifone jitters

This "jitteriness" must be pretty common. I overhauled the
the deflection board and HV board (with new Wintron) for my Quantum's
Amplifone and had the same problem. With mine it is in
the deflection board because when I substitute the board
the problem goes away. I want to describe it as "spiking". The
image just sort of jumps around on mine. We could not find the
the cause of it.

Bob Wood

Al Warner wrote:

> I'm not very good when it comes to technical things like these, but I have a
> problem like you mention with my Star Wars where the screen's contrast changes
> and everything gets bigger when the Death Star explodes. I think the condition
> you mentions happens too. I was wondering if it was suppose to do that, I guess
> it isn't. I'd like an answer to this question too!
>
> Thanks for asking it!
>
> -Al-
>
> Joel Rosenzweig wrote:
>
> > 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 11:21:05 1998