Magnavox Ch # 27z101-00aa

[Charlie East]

Cust stated no audio and only a line across the screen.. Found R445 burned,
so the vert chip is probably fried to.Dont have a schematic, Could the
sound chip(la4270) be using the same B+ as the vert chip? Anyone have the
value for R445?
Charlie

 

[Ol' Duffer]

Cust stated no audio and only a line across the screen.. Found R445 burned,
so the vert chip is probably fried to.Dont have a schematic, Could the
sound chip(la4270) be using the same B+ as the vert chip? Anyone have the
value for R445?

Overheating vertical IC is usually caused by failure of bootstrap
capacitor. Look for 100uF 35V near vertical IC. Resistor is
1 Ohm, functions mainly as a fuse. Haven't looked at the
schematic, but sound usually has its own supply.

 

[David]

R445 and R420 supply the + and - voltage to the vertical ic. 1 ohm
1/3 watt metal film flameproof. The diodes are also known to go
leaky, plus make sure the connections to the vertical ic are clean and
soldered well to the board. If the vertical ic is on the big metal
strap on the back of the chassis make sure it is not loose, otherwise
the connections will crack again.

David

 

[Charlie East]

Fixed, Vert chip, Audio Chip, and the resistors feeding them, plus a couple
of caps in the vert section, one was a 100@35
Thanks guys
Charlie

 

[RonKZ650]

Make sure also the anode lead coming out of the high voltage transformer is not
bad. I had a similar set a few weeks ago that burned up a vertical output IC
every day at the customers home, but would play endlessly in the shop. Even
running a wire hooked to chassis ground near the flyback would not make it arc,
but finally it did arc, about 2" to my hand. Ouch!
Ron