T
Tim Armstrong
- Jan 1, 1970
- 0
Attached is the schematic of a Magnavox chassis, I am experiencing trouble
with the resistor R432 burning. The symptoms are:
1. plug in the TV, the turns on and R432 starts to get very hot.
2. The screen is blank (sometimes just very dark), and no sound.
3. If I turn the TV on, the sound comes on and the TV plays fine and R432
stops getting hot.
3. The voltage on the base of Q402 changes when TV is shut on and off, so it
appears to be a problem that is in the schematic attached.
4. If I turn the TV off (screen darkens and sound shuts off), R432 starts to
get hot again and will burn up.
What I have did:
1. Replaced IC410 and C432 (filter cap).
2. Did simple ohm meter short-out test on Q402, Q420, and Q400
3. Checked values of all resistors around IC410
4. Replaced C431.
My (current) guess:
1. That Q402/420 is bad, can a transistor be bad, even if it passes the
normal 'diode' test?
My main business is computer repair, but I have had so many inquiries to
repair some TVs that I thought I would start taking on some extra business.
I have not repaired TVs (used to repair all the time), in about 15 years so
I am very rusty. Any help would be greatly appreciated.
with the resistor R432 burning. The symptoms are:
1. plug in the TV, the turns on and R432 starts to get very hot.
2. The screen is blank (sometimes just very dark), and no sound.
3. If I turn the TV on, the sound comes on and the TV plays fine and R432
stops getting hot.
3. The voltage on the base of Q402 changes when TV is shut on and off, so it
appears to be a problem that is in the schematic attached.
4. If I turn the TV off (screen darkens and sound shuts off), R432 starts to
get hot again and will burn up.
What I have did:
1. Replaced IC410 and C432 (filter cap).
2. Did simple ohm meter short-out test on Q402, Q420, and Q400
3. Checked values of all resistors around IC410
4. Replaced C431.
My (current) guess:
1. That Q402/420 is bad, can a transistor be bad, even if it passes the
normal 'diode' test?
My main business is computer repair, but I have had so many inquiries to
repair some TVs that I thought I would start taking on some extra business.
I have not repaired TVs (used to repair all the time), in about 15 years so
I am very rusty. Any help would be greatly appreciated.