"Franc Zabkar" bravely wrote to "All" (18 Feb 05 19:39:10)
--- on the heady topic of " Panasonic 27" TV w/ no vertical deflection"

FZ From: Franc Zabkar
FZ Xref: aeinews sci.electronics.repair:10853

FZ On Thu, 17 Feb 2005 20:53:47 -0500, "Steve W. Neas" put
FZ finger to keyboard and composed:

I have a TV with no vertical deflection, just the horizontal line
across the center.
It is a Panasonic PV-27D52, chassis KM-D2702, from 2002.

I checked the supply voltages to the vertical deflection chip
(LA7837).
Vcc (pin 1) was 23V (should be 12), and the pump-up supply voltage
(pin 8) was 28.4V (should be 24).
I removed the chip, and Vcc went to 11.8, and the pump-up V went to
29.4.

FZ It seems to me that the IC is bad. AFAICS, there must be an internal
FZ leak between the Vcc8 and Vcc1 supply pins. The 12V rail on Vcc1
FZ probably supplies other ICs in the set. Hopefully Vcc1 is current
FZ limited (by a 100 ohm series resistor?), otherwise those other ICs
FZ would be damaged. After replacing the IC, I'd check to see that this
FZ resistor, if it exists, has not been heat stressed.


If there is an external diode close to the LA7837 pins change it too.

A*s*i*m*o*v

.... The first rule of intelligent tinkering is to save all the parts.