Thread: Cross ref "?"
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Ricky Eck
 
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Default Found the resistor..


Well, I think I found the resistor. It was the one I suspected in a
previous post. It is actually kinda small. 1 ohm. But I traced it down,
from the 24v pin on the Vert chip, on back. It is sitting next to the
Flyback, and it is the one that has the burn mark on the bottom. And the
one that is on the old board, that I pulled the chip from, also has a 1 ohm
resistor on it, in almost the same place.

Now, if I can figure out the cap problem, then I may be on the way.. LOL
This can be any kind of flameproof resistors design not just the big
sand blocks. They actually looks like dull flat texture of a typical
axial resistors in many different wattages. They're designed not to
flame out when it overheats then opens, it simply chars into ashes or
almost intact, have to check with meter. The markings can be typical
resistor color codes or numbers printed on it.

The vertical's diode's anode (arrow) leads back to the diode &
flameproof resistor (but in some very cheap TV they omitted that
"safety" flameproof resistors, just a diode) to the flyback
transformer's one of many pins. The 26V source feeds both diode and
the vertical IC power pin.
The cathode (the bar that arrow is pointing to) of that diode near the
vertical IC both goes to the positive side of 100uF capacitor and to
the vertical IC. The minus side of said capacitor also goes to the
another pin on vertical IC.

Google the IC part number for example LA7838 (same as LA7837) turns
up:

http://www.steveselectronics.com/files/LA7838x.pdf

This will show you example circuit of this typical vertical circuit
design. This is just to help you understand the circuit better but
not all of the is used, TV makers uses slightly different designs but
basic vertical circuit is very similar based on LA7837/LA8738).

The other cap across ground to power supply for the vertical is a
filter, the other one like 100uF connected to pin 9 of vertical IC is
the one you want to change.

Hope this helps!

Cheers,

Wizard