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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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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. |
#2
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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. |
#3
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"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? |
#4
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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? |
#5
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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. |
#6
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"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. |
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