27" Magnavox tv model:XS2744A402,chassis:27Y104-00A

[Sidney]

27" Magnavox stereo tv model:XS2744A402,chassis:27Y104AA,year:Aug
1993,wood grain immitation case.One day the tv would not turn on upon
troubleshooting I found the following to be defective:

Q502=S2055AF=Philips # 4835 130 47897=NTE # NTE2353=2SD1878
F401=2.5 amp fuse
C432=100 Uf,200v

bad solder on:
R504
R524
R400A=degauss thermistor
K400=relay

I checked:

IC400=STR30130
R403=1.5 ohm,7w
Q400=TIP47=Philips # 4835 116 57108=NTE198

and they are fine but I briefly could not find R432=1K ohm,1/2w so why
would the Q502=HOT fail? and is F401 a pico fuse?if so my local
supplier only has a 2 amp or 3 amp which can I use?.Thanks in advance
for help.

Sidney
E-mail:[email protected]
Dartmouth,Nova Scotia
Canada

 

[RonKZ650]

Either 2 or 3a should be OK. Did you resolder the horiz driver
transformer? 90% of time that's why the horiz output shorts.

 

[Ol' Duffer]

and they are fine but I briefly could not find R432=1K ohm,1/2w so why
would the Q502=HOT fail?

When C432 goes bad, the regulator becomes unstable and the
output voltage goes up to about 145 Volts. HOT dissipates
more at the higher voltage, plus the horizontal drive
resistors get hot and crystalize their solder and the
drive to the HOT gets weaker so it spends even more time
in the linear zone.

and is F401 a pico fuse?if so my local supplier only has
a 2 amp or 3 amp which can I use?.

As a practical matter, a 3 will still blow if anything
serious goes wrong, and fuses are not exactly high precision
parts.

 

[Ol' Duffer]

Either 2 or 3a should be OK. Did you resolder the horiz driver
transformer? 90% of time that's why the horiz output shorts.

Not even 10%. It's almost always the 130V supply cap.
I see these on a regular basis.

 

[RonKZ650]

Well, the cap is always open, that's a fact, causes 130v supply to run
high, you get horiz sync problems, horiz jitter, the resistors get hot,
but that never shorts the horiz output, the solder connections do that.
Don't resolder the driver transformer, replace the cap and try it.