My Halicrafters model S38C gets a faint sound of a station that comes and goes at times. I have recapped and checked tubes with no change. Is it the IF transformers and, if so, how do I repair them?

You may just need to do a tuner/IF alignment...

:You may just need to do a tuner/IF alignment...
:
= = = = =

Yes, if the radio receives anything at all the IF transformers are probably intact; but they may need to be "peaked" vis a vis the alignment procedure.
Same goes for the radio's front end... if the set doesn't respond to a total alignment, I'd suspect the antenna coils and/or the bandswitch- an open coil or oxidized switch contact could result in severe signal attenuation. However, this shows up usually on just one band- it's unlikely to have multiple band failures.

I have one of these sets and it is a decent performer but it needs a reasonably long antenna to work well- at least 15 feet.

Finally, tubes which "test good" aren't necessarily "good tubes". I've heard it said that while tube testers can always detect a bad tube, they can't be 100% relied on to find good tubes.

I have a negative 5volts dc on the first grid of the 12SA7 and scope shows the osc is running. When I touch the scope probe to the plate of the 12SA7 the radio suddenly springs to life a little. Only have about 79 volts dc on plates. Seems low to me.

::You may just need to do a tuner/IF alignment...
::
:= = = = =
:
:Yes, if the radio receives anything at all the IF transformers are probably intact; but they may need to be "peaked" vis a vis the alignment procedure.
:Same goes for the radio's front end... if the set doesn't respond to a total alignment, I'd suspect the antenna coils and/or the bandswitch- an open coil or oxidized switch contact could result in severe signal attenuation. However, this shows up usually on just one band- it's unlikely to have multiple band failures.
:
:I have one of these sets and it is a decent performer but it needs a reasonably long antenna to work well- at least 15 feet.
:
:Finally, tubes which "test good" aren't necessarily "good tubes". I've heard it said that while tube testers can always detect a bad tube, they can't be 100% relied on to find good tubes.
:

:I have a negative 5volts dc on the first grid of the 12SA7 and scope shows the osc is running. When I touch the scope probe to the plate of the 12SA7 the radio suddenly springs to life a little. Only have about 79 volts dc on plates. Seems low to me.
:
= = = = = = = =

It is low. Should be in the neighborhood of 130VDC.
Something is severely loading down the B+ bus; or your rectifier tube is punking out. Check for a reversed filter electrolytic cap, and that the red and blue leads to the first IF transformer don't have bare wire exposed and in contact with something else.

John: you will find a lot of S-38 discussion and help on the Antique Radio Forum, in the Communication Receivers section.

http://www.antiqueradios.com/forums/viewforum.php?f=5

Rich
>>>>>>>>>>>>>>>>>>>>>>>>>>>><<<<<<<<<<<<<<<<<<<<

:I have a negative 5volts dc on the first grid of the 12SA7 and scope shows the osc is running. When I touch the scope probe to the plate of the 12SA7 the radio suddenly springs to life a little. Only have about 79 volts dc on plates. Seems low to me.
:
:
:
:
:::You may just need to do a tuner/IF alignment...
:::
::= = = = =
::
::Yes, if the radio receives anything at all the IF transformers are probably intact; but they may need to be "peaked" vis a vis the alignment procedure.
::Same goes for the radio's front end... if the set doesn't respond to a total alignment, I'd suspect the antenna coils and/or the bandswitch- an open coil or oxidized switch contact could result in severe signal attenuation. However, this shows up usually on just one band- it's unlikely to have multiple band failures.
::
::I have one of these sets and it is a decent performer but it needs a reasonably long antenna to work well- at least 15 feet.
::
::Finally, tubes which "test good" aren't necessarily "good tubes". I've heard it said that while tube testers can always detect a bad tube, they can't be 100% relied on to find good tubes.
::
:
:

I have a real good playing S38A and measured plate voltage at 88v so mine of 79 is not that far off. I replaced all the tubes with the ones from the 38A set and no change. When first turned on the set plays for about 1 second, but not real loud, then dies down to nothing usually.

:John: you will find a lot of S-38 discussion and help on the Antique Radio Forum, in the Communication Receivers section.
:
:http://www.antiqueradios.com/forums/viewforum.php?f=5
:
:Rich
:>>>>>>>>>>>>>>>>>>>>>>>>>>>><<<<<<<<<<<<<<<<<<<<
:
:
::I have a negative 5volts dc on the first grid of the 12SA7 and scope shows the osc is running. When I touch the scope probe to the plate of the 12SA7 the radio suddenly springs to life a little. Only have about 79 volts dc on plates. Seems low to me.
::
::
::
::
::::You may just need to do a tuner/IF alignment...
::::
:::= = = = =
:::
:::Yes, if the radio receives anything at all the IF transformers are probably intact; but they may need to be "peaked" vis a vis the alignment procedure.
:::Same goes for the radio's front end... if the set doesn't respond to a total alignment, I'd suspect the antenna coils and/or the bandswitch- an open coil or oxidized switch contact could result in severe signal attenuation. However, this shows up usually on just one band- it's unlikely to have multiple band failures.
:::
:::I have one of these sets and it is a decent performer but it needs a reasonably long antenna to work well- at least 15 feet.
:::
:::Finally, tubes which "test good" aren't necessarily "good tubes". I've heard it said that while tube testers can always detect a bad tube, they can't be 100% relied on to find good tubes.
:::
::
::
:
:

I would also check all resistors in the unit. A drifting or bad one can wreak havoc on the receiver if it's in a critical IF circuit.