Quote:
Originally Posted by old_tv_nut
What you called the "ground" of the tripler is not ground, it is just the low point and has some positive voltage on it due to being connected to ground through the other parts of the circuit, not directly to ground. If the Zener was connected on both ends to ground, it would indeed be doing nothing.
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I think TCA is taking tripler ground to mean GROUND and of course its not.
OK TCA the "ground" on the tripler is grounded in SOME sets.
On those the ABL will usually be taken at R356, the "low" end of the
FBT HV winding.
Think of yours as the low side of the tripler.
R362 & R359 will have the HV current through them, the brighter
the pix the more current so more voltage across the resistors.
The Zener diode will keep the voltage at its cathode at
7.5 V or less.
Under 7.5V the zener does nothing.
Result is the ABL control will adj. between apx 0 V & 7.5 V
If a dark pix it will adj. between 0 & < 7.5 V & send that to the
ABL transistor.
Hope that helps
73 Zeno
