TV keeps blowing audio IC
 

Thought I had this little 9" TV working, but another even tougher problem
has popped up. After I originally fixed the set, I ran it for several hours
without any problems. Unplugged it and closed up for the night. When I
plugged it in and turned it on the next day, the volume was stuck on full
blast. I replaced the an IC which serves as the audio OP, volume control,
and mute; I also checked for bad caps and cold solder, and measured the
voltages on the IC to make sure they were correct. Set works great for a few
more hours, again I unplug it and close up. Once again, the next time I
power it, the sound is full blast. I only have one more IC left, and I'm not
installing it until I know what the underlying problem is!
A note about this set; when switched to radio, it uses the same audio IC.
The IC is powered by a separate power supply, not from the TV flyback.
What am I missing??
BTW please see my previous post "Yoke Replacment" for info about the
previous repair.

maybe static charge of crt to speaker or chassis.
Check crt grounding if ok and speaker is close to crt run a ground to
the speaker frame useing a resistor maybe 1 k.

"Chris F." wrote in message
...
Thought I had this little 9" TV working, but another even tougher
problem
has popped up. After I originally fixed the set, I ran it for several
hours
without any problems. Unplugged it and closed up for the night. When I
plugged it in and turned it on the next day, the volume was stuck on full
blast. I replaced the an IC which serves as the audio OP, volume control,
and mute; I also checked for bad caps and cold solder, and measured the
voltages on the IC to make sure they were correct. Set works great for a
few
more hours, again I unplug it and close up. Once again, the next time I
power it, the sound is full blast. I only have one more IC left, and I'm
not
installing it until I know what the underlying problem is!
A note about this set; when switched to radio, it uses the same audio
IC.
The IC is powered by a separate power supply, not from the TV flyback.
What am I missing??
BTW please see my previous post "Yoke Replacment" for info about the
previous repair.



Did you check the voltage of the power supply at the IC?

Yup, 12V dead on just as the specs dictate.

"James Sweet" wrote in message
news:BBsqe.772$9a1.216@trnddc01...

"Chris F." wrote in message
...
Thought I had this little 9" TV working, but another even tougher
problem
has popped up. After I originally fixed the set, I ran it for several
hours
without any problems. Unplugged it and closed up for the night. When I
plugged it in and turned it on the next day, the volume was stuck on
full
blast. I replaced the an IC which serves as the audio OP, volume
control,
and mute; I also checked for bad caps and cold solder, and measured the
voltages on the IC to make sure they were correct. Set works great for a
few
more hours, again I unplug it and close up. Once again, the next time I
power it, the sound is full blast. I only have one more IC left, and I'm
not
installing it until I know what the underlying problem is!
A note about this set; when switched to radio, it uses the same audio
IC.
The IC is powered by a separate power supply, not from the TV flyback.
What am I missing??
BTW please see my previous post "Yoke Replacment" for info about the
previous repair.



Did you check the voltage of the power supply at the IC?

That's what I'm wondering too, since it only seems to fail on powerup. I
will check that out.


"Doug" wrote in message
oups.com...
maybe static charge of crt to speaker or chassis.
Check crt grounding if ok and speaker is close to crt run a ground to
the speaker frame useing a resistor maybe 1 k.

"Chris F." wrote in message
...
That's what I'm wondering too, since it only seems to fail on powerup. I
will check that out.



Did you check the voltage at powerup too to make sure it doesn't spike?
Unlikely but possible.