Re: Video Goes Away After 1-3 minutes

A 'spot killer' is a circuit in the monitor that cuts of the image (by lowering the intensity to nil) when it senses that there is no input signal (x/y deflection) present. It exists to prevent the monitor from burning a spot in the center of the CRT from being powered on with no input signal. Most vector monitors have one. They typically have a red LED in them that illuminates when the circuit is active. That is, if there is a normal input signal, and the monitor is not trying to 'kill a spot', the LED will be off. If you see a red LED lit on the chassis, the spot killer is active, and you should not expect to see anything (unless you turn the brightness all the way up perhaps). So the question is another way of asking if the LED in your monitor lights up when the image disappears.

'Vector chatter' is the distinctive sound made by the monitor circutry (mostly the deflection coils, I think) when it is working 'normally'. If you monitor is working fine for a couple of minutes before the image disappears, listen to it carefully before and after it disappears to determine if it changes.

These questions are intended to help narrow down the myriad potential sources of the problem. In general, it's nice to first determine if the problem is the monitor or the game PCB. A spare PCB or monitor (or oscilloscope) are useful but not required here. I also like to rule out connector/terminal issues early, as they are common. If it is a monitor problem, you'll want to determine if it's a problem with the power supply, deflection amp(s), spot-killer, or HV circuits.

If the spot killer comes on, it points toward an issue with the deflection amp(s) or the game PCB (or possibly the spot killer circuit itself). If the spot killer doesn't come on, and deflection chatter is still heard, then perhaps the HV or the Z circuits.

df

--- On Tue, 8/31/10, Tim Soderstrom <tim@moocowproductions.org> wrote:

> From: Tim Soderstrom <tim@moocowproductions.org>
> Subject: Re: VECTOR: Video Goes Away After 1-3 minutes
> To: vectorlist@vectorlist.org
> Date: Tuesday, August 31, 2010, 5:39 PM
> Not sure what a spot killer is? I
> believe I can hear the usual high pitched noise coming from
> the CRT so it is getting some sort of power. I can turn the
> brightness up on the flyback and I don't see a spot. When it
> cuts out I hear sort of an electrical clicky sound.
>
> Also not sure what Vector chatter is, but if it's what I
> think it is (audible changes when rendering vector images)
> then no I don't hear anything after it goes out.
>
> Alas, I have neither a spare board nor monitor :(
>
> On Aug 31, 2010, at 12:51 PM, Mark Shostak wrote:
>
> > Is the spot killer coming on, when the video goes
> away?
> >
> > Do you hear "vector chatter" when the video goes
> away?
> >
> > Do you have a spare board or spare monitor you can
> swap in?
> >
> > -M
> >
> > On Tue, Aug 31, 2010 at 12:29 PM, Tim Soderstrom
> > <tim@moocowproductions.org>wrote:
> >
> >> I have a Space Duel cabinet with a WG vector
> monitor. It has the LV2000
> >> voltage mod and has been working well for quite a
> few years. Recently,
> >> though, it has stopped working properly. It
> sometimes shows proper video for
> >> about 1-3 or so minutes, after which the video
> cuts out like the monitor is
> >> not getting power.
> >>
> >> The HV board with the LV2000 has the LEDs powered
> up. I suspect it's the
> >> flyback but do not otherwise know how to fix that.
> I also noticed a while
> >> (with I think a blue stripe) wire that is not
> connected to anything also on
> >> the HV board. I think it's been that way for quite
> some time and doesn't
> >> seem to affect anything though I am not sure as to
> what the wire does (or
> >> where it goes).
> >>
> >> Anyone have any thoughts on what I should be
> doing? Since the tube is good
> >> I hesitate to swap it out for an LCD and use the
> VectorVGA stuff.
> >>
> >> Thanks!
> >>
> >> Tim
> >>
> >>

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Received on Tue Aug 31 21:54:49 2010