Question about Insignia IS 20" TV040919 TV
The input keeps switching back and forth on this tv by itself and we can't get it to stop. If you hold down any button, either on the tv or the remote it will stop switching, but as soon as you let the button go, it starts to switch back and for again... what is going on?
I repaired it!
My Insignia TV set started showing the same problem reported here, after a static discharge sparked when my wife was cleaning the TV with a cloth.
The information provided by bill47 proved to be very useful. I tried to find the data sheet of the large 64 pin IC, TDA973, I found the TDA 9351, which may be from the same family. I measured the voltage at pin 6 and it was approx. 0.2V. I imagined that if I forced that voltage to a higher value the IC would believe that no button is deppressed and so return to normality. From bill47 comments and my measurements of resistance to ground with the TVset off I estimated that a voltage divider was formed with a 3.3K resistor from +3.3V to pin 6 and 180 ohm to pin 6 to ground. In those conditions, I calculated that if I add a 18 ohm resistor from 3.3V to pin 6 I should force the voltage at that pin to 3V. I first tried with a 120 ohm resistor between pin 61 (peripherial power supply in) (+3.3V) and pin 6. This moved the voltage to 1.7V, the failure persisted, but the effect was different, as if another button, located at the rigth of the Input button, was permanently depressed. This showed me that I was in the right trak. I refined my calculations and replaced the 120 ohm resistor to 15 ohm. That raised the voltage at pin 6 to 2.5 V, and solved the problem. The front panel buttons were disabled (except for the Power button), but that is not a problem, I never use them, I always use the remote control. So I can continue enjoying my Insignia TV set! Thank you bill47 and all the other people who posted their comments.
Posted on Mar 30, 2009
Purchased the service manual, and traced problem to the "KEY" input (pin 6) of the Philips universal TV processor chip (TDA9373 - the large 64 pin DIP on the main PCB). This single pin connects to all the front buttons/momentary switches making it extremely vulnerable to ESD strikes. Each of these switches is configured in a "resistor ladder" voltage divider circuit, which produces a unique voltage at pin 6 for each of the 7 switches. When no key is pressed the voltage on this pin should be around 3.3V (via 3.3K pullup to the 3.3V supply). My defective unit measures only 0.17 volts -- suggesting ESD damage. This condition confuses the processor (thinks a key is constantly being pressed) which explains the behaviour of constantly changing inputs, etc. In my case the front panel power button still operates because it shorts the input to ground (zero volts) which is still properly detected. Unfortunately the only remedy is to replace the part, which is likely fairly expensive. Because there is a microprossesor core in this device, it may have to be purchased directly from Insignia/Haier to ensure it is programmed correctly for the particular TV model. (Have not yet checked price/availability.)
Sorry for the bad news!
Posted on May 08, 2008
What is ESD? is that that I have to change?
any idea where can I buy it?
I was looking for Insignia/Haier but I didn't find something
Posted on Jul 07, 2008
So should i be assuming that it worked ?
Posted on Jan 23, 2008
Just sat on hold with tech support for over a half hour, someone finally came on and said this:
Unplug your TV, and disconnect everything you have attached to your tv (antennas, cable wire, input cables from VCR/DVD/cable box, EVERYTHING) and let it sit for about a half-hour to allow the tv to return to its factory settings. Then, plug it back in and see if it works.
It has not been the full half hour yet, but if I don't repost here, then assume that this solution works!
Posted on Jan 23, 2008
Any one find any tricks that make it work?
Posted on Dec 25, 2007
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Posted on Jan 02, 2017
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