Schematics for sync kill circuit (outside of 15.75 range)?

[MonitorGuru]

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[rchadd]

i am interested in this circuit also

i figure such a circuit would do similar to what a jpac does? protect monitor from damage if >15Khz signal is applied by the video card.

i want to build a cheap mame machine to connect arcade figure i'd used dos advancemame and supported video card that will give 15KHz output

i think problem will be with initial boot screesn before the machine goes into advancemame - is signal going to be >15KHz? Will it damage the monitor?

in my previous machine i used an ArcadeVGA but i dont want the expense.

luckilly i already have a video amp - which i think will also be required

[krick]

i figure such a circuit would do similar to what a jpac does? protect monitor from damage if >15Khz signal is applied by the video card.

i want to build a cheap mame machine to connect arcade figure i'd used dos advancemame and supported video card that will give 15KHz output

i think problem will be with initial boot screesn before the machine goes into advancemame - is signal going to be >15KHz? Will it damage the monitor?

Yep.  the J-Pac divides the signal in half if it is out of range in order to protect the monitor.

With any video card (except the ArcadeVGA), the inital boot screen will damage an arcade monitor without some sort of protection like a J-Pac or a similar circuit.

Has anybody actually examined a J-Pac to figure out this circuit?

[richms]

If I was engeneering this, I would use a 555 timer in oneshot mode triggered by the sync and the output holding the sync line low so that the next sync will not get thru. It wont help for under speed syncs, but it will result in whatever is being fed into it being divided down to something less then 15kHz (or whatever you choose the duration of the timer to allow thru)

Would be easier on a microcontroller tho.

[SirPeale]

The video amp from Ultimarc also appears to have this circuit (based on what it does in one of my cabinets).  For $15 it might be a cheaper solution.

[rchadd]

The video amp from Ultimarc also appears to have this circuit (based on what it does in one of my cabinets).

[SirPeale]

I dunno.  I was told (not by Andy) that the amp didn't have the circuitry, but Andy mentioned at some point he was going to incorporate it in there.  Maybe he did, because the signal on my is certainly cut in half.

[rchadd]

I dunno.

[SirPeale]

did you recently purchase the amp?

mine is over 1 year old now never been used

Yes.  It was about...oh...six months ago I think.