CurtPalme.com Home Theater Forum

[tse]

The sealed pot on the neck card sets the level of the OVER-I signal. The OVER-I signal is proportional to CRT beam current. It goes to the VIM bd where if it exceeds the threshold it causes the projector to shut down. There is another current sample type signal called I-SENS that comes from the neck card. It lowers the contrast setting of the projector when the current is too high, like a full white field. The I-SENS signal should do it's thing at a lower level than the OVER-I so high currents are controlled without shutting off the projector. The OVER-I circuit is there if the projector looses control of the beam current, like if something breaks and the contrast no longer has control.

There is nothing to be gained by messing with the pot. What you have to lose is controlled shut down in case of over current in a CRT if something causes full conduction or shutdown of the projector on bright scenes for no good reason.

Scott

[zGman]

Hi Scott,
That is some good info - Thanks.
I have wondered if the beam current settings are the
difference between the 9" and 8" neckboards? And if
using the 8" neckboards on a 9" tube set would have
an appreciable difference on the overall light output?
Cheers,
Galen

[Nashou66]

Thanks for the clarification Scott.

Athanasios

[Robert A. Hill]

Scott,
What provides the equivalent controls for the Ampro x600 series? Luckily, I have not seen a high beam current error, but others have posted about this issue.

[tse]

With the Ampro projectors a HV current sample is sent from the HVPS to the CPU card. If it goes too high the CPU shuts things down and displays the HIGH BEAM CURRENT message.

Scott

[AnalogRocks]

[AnalogRocks]