🚀 go-pugleaf

On 19 Jul 2005 08:01:53 -0700, "alitonto" <alitonto@hotmail.com> put
finger to keyboard and composed:

>
>
>dkuhajda@locl.net wrote:
>> Why do you think the AGC is the problem and not a symptom?
>> Do some research to find out what the function of the AGC voltage is
>> for and how it works?
>
>Thank you all.
>I would like to do this test but I need to check about correct
>procedure: would it be proper to solder a 3.9 zener diode with the -
>end to the tuner's AGC pin and the + end to the tuner's ground.
>I understand the idea is to clamp the voltage to 3.9; is this right?
>I will wait for confirmation.
>Al.

AGC = automatic gain control

If the signal from the tuner is low, then the AGC circuit attempts to
compensate by increasing the gain of the RF amp. Conversely, if the
signal is strong, then the AGC circuit reduces the gain. Under typical
(ie good) signal conditions the AGC circuit would be producing a
control voltage of 3.9V. The gain is automatically controlled via a
closed loop feedback system that monitors the signal level at the IF
stage.

If you suspect an AGC fault, then disconnect the AGC input and connect
the tuner's AGC pin to a potentiometer via a series resistor, as
follows:


  tuner AGC pin    o---- R ------|
                                 |
                                \|/
                                 |
            tuner ground o--/\/\/\/\/\--o tuner supply (+12V)
                           potentiometer


- Franc Zabkar
-- 
Please remove one 's' from my address when replying by email.