testing and measuring for AVC

10/4/2007 10:57:26 AMBrian

The battery set I'm working on (Philco 37-38) has a 1H4 for the AVC. How can I test the circuit to see if it is working?

10/4/2007 11:16:59 AMRadiodoc

:The battery set I'm working on (Philco 37-38) has a 1H4 for the AVC. How can I test the circuit to see if it is working?

10/4/2007 11:25:35 AMRadiodoc

Brian,

You should be able to measure the AVC minus voltage between chassis/ground and the junction of R21 and the brown wire (if the wire color is still readable) from the 2nd IF transformer. This would be the side of R21 away from the junction of R21/R20/plate of 1H4 tube. There will probably be some steady minus DC voltage there but should increase to some value when a station is tuned in or a signal is applied from a signal generator.

Radiodoc
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:The battery set I'm working on (Philco 37-38) has a 1H4 for the AVC. How can I test the circuit to see if it is working?

10/4/2007 11:28:35 AMRadiodoc

:Brian,
:
:You should be able to measure the AVC minus voltage between chassis/ground and the junction of R21 and the brown wire (if the wire color is still readable) from the 2nd IF transformer. This would be the side of R21 away from the junction of R21/R20/plate of 1H4 tube. There will probably be some steady minus DC voltage there but should increase to some value when a station is tuned in or a signal is applied from a signal generator.
:
:Radiodoc
:***********

Brian,

I should have said the brown wire from the 1st IF transformer.

Radiodoc
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:
::The battery set I'm working on (Philco 37-38) has a 1H4 for the AVC. How can I test the circuit to see if it is working?

10/4/2007 7:21:28 PMLewis Linson

::Brian,
::
::You should be able to measure the AVC minus voltage between chassis/ground and the junction of R21 and the brown wire (if the wire color is still readable) from the 2nd IF transformer. This would be the side of R21 away from the junction of R21/R20/plate of 1H4 tube. There will probably be some steady minus DC voltage there but should increase to some value when a station is tuned in or a signal is applied from a signal generator.
::
::Radiodoc
::***********
:
:Brian,
:
:I should have said the brown wire from the 1st IF transformer.
:
:Radiodoc
:***********
::
:::The battery set I'm working on (Philco 37-38) has a 1H4 for the AVC. How can I test the circuit to see if it is working?

And, be sure to use a VTVM or a DMM with a high impedence input (11 MegOhms) or you will load down the AVC bus, as an ordinary VOM will do.
Lewis