CurtPalme.com Home Theater Forum

[cmjohnson]

I should mention that the cap mod I mentioned earlier is not expected to improve the sharpness of focus. Not directly. It should instead improve the efficiency of the focus system, allowing the focus board to run more efficiently, draw less power, and run cooler, thus
contributing to longer component life and (possibly) making the focus more stable over time and changes in internal projector temperature,
which I think is a worthwhile improvement in and of itself.

CJ

[cmjohnson]

Another note: While studying the Marquee service manual, I picked up on a fact that had previously escaped my notice.


The VERTICAL rate dynamic focus adjustments are applied to the STATIC focus coil, NOT the dynamic coil.

Only the corrections applied at the horizontal scan rate are applied to the dynamic focus coil.


This does have a few implications for the Frankenyoke project: It means that it's just as important to establish the correct
coil inductance value for the static coil as it is to establish the correct value for the dynamic coil.


If you were only to optimize the static coil, you might find that you would have problems achieving good central focus,
while having no issues with focusing toward the edges of the screen.

In fact, I've seen that happen, with non-optimized yokes. They could generate enough field strength to focus the corners via the
dynamic winding, but didn't have enough strength to correct the central area of the screen via the dynamic winding.


CJ