Re: How to confirm a TV tuner is at fault?

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#523

From: Ken Taylor
Date: Tue, 19 Jul 2005 01:43

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"alitonto" <alitonto@hotmail.com> wrote in message 
news:1121735112.965997.169800@f14g2000cwb.googlegroups.com...
> Thanks Phil
> Although your suggestion sounds interesting, are you suggesting that
> tuners should have a voltage adjustements in place?
> I am sorry but I am confused as to what is there to gain from trying
> your suggestion.
> I guess what I am trying to establish is if the higher voltage
> appearing at the AGC pin could be caused by another circuit part or IC
> etc.
> Thanks.
>

It's a test. If you drag down that voltage to 3.9V and the tuner works, you 
know it is not at fault.

Ken


> Phil Allison wrote:
>> "alitonto"
>> >
>> > re Teac TV ctm687 This is further to my previous post 17/7/2005.
>> > After performing many tests on the circuit I find the AGC voltage to be
>> > higher (7.84) than it is required at I/C TDA8305A (3.9).
>> > I am not sure what other things to try before actually desoldering the
>> > tuner.
>>
>>
>>  **  Try pulling that AGC voltage down to 3.9 volts or so.
>>
>>  Use a suitably chosen resistor to ground or maybe a 3.9 volt zener.
>>
>>  See what happens.
>>
>>
>>
>>
>> ........    Phil
>

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