Quote:
Originally Posted by JesusJones
This sounds like it could very well be the case. But like I said before I have no Idea what the agc loop is. Could some one tell me where this is? what it is?
|
If you look at the control grids of each pix IF stage in a typical set you will see that the grid receives a negative bias which should grow stronger with stronger signal. Because it is the practice to use "remote cutoff" pentodes in the IF stages the increasing negative bias with stronger signal causes a cutback on total IF string gain, preventing overload. The AGC line feeds off the video detector as a rule, and supplies this negative bias. A shorted or leaky bypas capacitor from the line to ground may kill the AGC action altogether.
Sometimes it is simply that in fiddling around with a set that an actual AGC trimpot may have been disturbed, knocking the AGC out of adjustment, meaning that you could probably solve your problem with a simple tweak. These AGC level adjustments are usually found only on the higher-priced more elaborate sets, while most other more basic sets usually don't have such an adjustment.