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vertical trouble!!

R

Rono

Jan 1, 1970
0
Toshiba TV28C30 T.V.! Replaced vertical IC, &
all the regular capacitors, but set still pulls the 24 volt
line down! Diode bt IC is ok! Ideas?? Rono.
 
T

Tom MacIntyre

Jan 1, 1970
0
Toshiba TV28C30 T.V.! Replaced vertical IC, &
all the regular capacitors, but set still pulls the 24 volt
line down! Diode bt IC is ok! Ideas?? Rono.

Some sets use a zener diode to clamp the 24-28 volt line. This may be
shorted. Probably not, though, as this is usually a crowbar circuit.

Do you have a DC supply with good current limiting? If you apply a
voltage from such a supply (with the current threshold set low) to the
24 VDC rail while successively removing ground paths (set turned off),
you'll find it when the current draw suddenly decreases. This is a
very effective way of troubleshooting power supplies.

Tom
 
T

Tom MacIntyre

Jan 1, 1970
0
Some sets use a zener diode to clamp the 24-28 volt line. This may be
shorted. Probably not, though, as this is usually a crowbar circuit.

Do you have a DC supply with good current limiting? If you apply a
voltage from such a supply (with the current threshold set low) to the
24 VDC rail while successively removing ground paths (set turned off),
you'll find it when the current draw suddenly decreases. This is a
very effective way of troubleshooting power supplies.

Tom

Make that a low voltage, 5 VDC or so.

Tom
 
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