RCA F27732SB TV Blows Fuse

[[email protected]]

Hi everyone,

I have recently encountered a problem with my RCA 27" TV. The TV blows
the fuse every time it is plugged in. I am unable to do voltage tests
as there is NO power. I believe the problem is within the first few
components (filter capacitor, diodes, chopper transistor, etc). I have
not really taken a very good look at the set, but would like some sort
of direction before I go ahead and start.

Can someone direct me to the right direction of which are the most
likely failed components?

Thank you

P.S. THE CHASSIS IS: CTC169CK5

 

[James Sweet]

Hi everyone,

I have recently encountered a problem with my RCA 27" TV. The TV blows
the fuse every time it is plugged in. I am unable to do voltage tests
as there is NO power. I believe the problem is within the first few
components (filter capacitor, diodes, chopper transistor, etc). I have
not really taken a very good look at the set, but would like some sort
of direction before I go ahead and start.

Can someone direct me to the right direction of which are the most
likely failed components?

Thank you

P.S. THE CHASSIS IS: CTC169CK5

Sounds like you pretty well nailed it. Check the chopper transistor and
rectifier diodes on the input first, and keep in mind that if one of those
checks bad, other parts in the area may be bad as well.

 

[[email protected]]

I have tested the 4 rectifier diodes and they all seem to be opened
(VOLTAGE DROP IN BOTH DIRECTIONS). Do you thing that these shorted
diodes could have shorted the IC regulator and the chopper transistor?
Thanks

 

[b]

I have tested the 4 rectifier diodes and they all seem to be opened
(VOLTAGE DROP IN BOTH DIRECTIONS). Do you thing that these shorted
diodes could have shorted the IC regulator and the chopper transistor?
Thanks

replace the diodes, remove the chopper transistor AND the PTC, and
power the set up with 100w bulb in series int he mains line. be wary
if it glows brightly. if it is dim or fades, you will know your
rectifier is probably ok now.
-B

 

[James Sweet]

I have tested the 4 rectifier diodes and they all seem to be opened
(VOLTAGE DROP IN BOTH DIRECTIONS). Do you thing that these shorted
diodes could have shorted the IC regulator and the chopper transistor?
Thanks

Are the diodes shorted or are they open? Did you test them out of circuit?

 

[[email protected]]

I believe the diodes are shorted as the voltage drop appears in both
directions. I tested them in the circuit. Do I get false readings if
they are in the circuit? Thanks.

 

[Mark D. Zacharias]

Do I get false readings if

they are in the circuit?

Very often - depends on the other components in the circuit. Only way to
know for sure is to test them out of circuit.

Mark Z.

 

[Meat Plow]

I believe the diodes are shorted as the voltage drop appears in both
directions. I tested them in the circuit. Do I get false readings if
they are in the circuit? Thanks.

Unsolder one leg of each device and retest using your meter's diode check
function. Often, in circuit tests can deceive.

 

[[email protected]]

Unsolder one leg of each device and retest using your meter's diode check
function. Often, in circuit tests can deceive.

In or out of circuit, bridges, if not short usually good, also take a
look at the output transistor next to the flyback on a heatsink, and
cold solders on the horiz. drive transformer. also older rca's have a
lot of bizarre problems due to their "on board" tuner, if you do
manage to get it on just go over the tuner to avoid future problems.
Shane.

 

[[email protected]]

Thanks
I will retest the diodes and I will try to replace them. I will also
test the chopper transistor along with HOT.
Also I have found 1 other diode shorted right near the chopper
transformer. Hmmmmm

 

[Meat Plow]

Thanks
I will retest the diodes and I will try to replace them. I will also
test the chopper transistor along with HOT.
Also I have found 1 other diode shorted right near the chopper
transformer. Hmmmmm

Consider yourself lucky it's not one of the older RCA sets that used two
SCR's to derive flyback scan.

 

[[email protected]]

Hi
I will try to test some HV components to determine how bad the short
really is and I will post again.

 

[[email protected]]

Hi again,
I was wondering, what could have caused all 4 rectifier diodes to
short?

 

[Meat Plow]

Hi again,
I was wondering, what could have caused all 4 rectifier diodes to
short?

What else have you found wrong? Is the set working now?

 

[[email protected]]

Hi
I am still working on the set. I have not gotten around to check it
out. At the moment I have removed all 4 rectifiers. I will test the
HOT and chopper today.

 

[b]

Hi again,
I was wondering, what could have caused all 4 rectifier diodes to
short?

could be several things - mains surge, bad ptc, bad chopper, shorted
mains capacitor... being common reasons in my experience. usually,
however, a fusible resistor opens first in the case of problems
further into the power supply .
-b