AVC voltage can be found at left side of R21 in the schematic. You can measure voltage at this point with a digital meter or VTVM. Voltage should go negative when a strong local station is tuned in.
Has cap 7, .05 mf, been replaced. Any leakage on this cap stops AVC action.
AVC is not perfect. There will still be differences in volume between strong and weak stations but not as much as without AVC. For AVC to properly operate a radio has to be aligned. If signals aren't seen as strong enough to generate AVC voltage there won't be any action. Measure AVC line first.
http://www.nostalgiaair.org/PagesByModel/204/M0013204.pdf
Norm
:I don't believe AVC is working in this set, as I must adjust volume downward for strong local stations as I tune the dial.
:Could someone tell me how to test for AVC? Would lack of AVC affect shortwave reception which is currently non-existent?
:Thanks
:Hi Brian
:
: AVC voltage can be found at left side of R21 in the schematic. You can measure voltage at this point with a digital meter or VTVM. Voltage should go negative when a strong local station is tuned in.
:
: Has cap 7, .05 mf, been replaced. Any leakage on this cap stops AVC action.
:
: AVC is not perfect. There will still be differences in volume between strong and weak stations but not as much as without AVC. For AVC to properly operate a radio has to be aligned. If signals aren't seen as strong enough to generate AVC voltage there won't be any action. Measure AVC line first.
:
:http://www.nostalgiaair.org/PagesByModel/204/M0013204.pdf
:
:Norm
:
::I don't believe AVC is working in this set, as I must adjust volume downward for strong local stations as I tune the dial.
::Could someone tell me how to test for AVC? Would lack of AVC affect shortwave reception which is currently non-existent?
::Thanks
That's a problem. AVC should vary by signal strength. The signal comes through a large value resistor R21 (1 meg) from the volume control and becomes negaive AVC voltage. Is the resistor open? 1H4 tube bad?
The line is biased through R20 so it's always negative but the signal from your 1H4 should make it more negative.
Try using an antenna. Are IF Transformers peaked?
Norm
:Negative voltage appears to be fixed, at 3 to 4 v.
:
::Hi Brian
::
:: AVC voltage can be found at left side of R21 in the schematic. You can measure voltage at this point with a digital meter or VTVM. Voltage should go negative when a strong local station is tuned in.
::
:: Has cap 7, .05 mf, been replaced. Any leakage on this cap stops AVC action.
::
:: AVC is not perfect. There will still be differences in volume between strong and weak stations but not as much as without AVC. For AVC to properly operate a radio has to be aligned. If signals aren't seen as strong enough to generate AVC voltage there won't be any action. Measure AVC line first.
::
::.pdf
::
::Norm
::
:::I don't believe AVC is working in this set, as I must adjust volume downward for strong local stations as I tune the dial.
:::Could someone tell me how to test for AVC? Would lack of AVC affect shortwave reception which is currently non-existent?
:::Thanks