I have an old 4 tube cathederal Austin radio that is not listed anyplace. It uses an 80, a 47 and two 24's. I recapped it and changed out-of-tolerance resistors. It runs OK but still quite a bit of hum even when the volume control is way down. It is a TRF. Would it need alignment or how can I get rid of the hum?

John

Did you use 10 mf @ 450 volt replacement filter caps? Are the originals disconnected? Hum with volume down is usually power supply filtering.

Norm

:I have an old 4 tube cathederal Austin radio that is not listed anyplace. It uses an 80, a 47 and two 24's. I recapped it and changed out-of-tolerance resistors. It runs OK but still quite a bit of hum even when the volume control is way down. It is a TRF. Would it need alignment or how can I get rid of the hum?
:

:John
:
: Did you use 10 mf @ 450 volt replacement filter caps? Are the originals disconnected? Hum with volume down is usually power supply filtering.
:
:Norm
:
::I have an old 4 tube cathederal Austin radio that is not listed anyplace. It uses an 80, a 47 and two 24's. I recapped it and changed out-of-tolerance resistors. It runs OK but still quite a bit of hum even when the volume control is way down. It is a TRF. Would it need alignment or how can I get rid of the hum?
::
:
:
Hi, you might have something in the house causing the set to hum, like a wall transformer or LED light. I have to turn on the hall light to get a clear signal on pretty much all of my radios. You can always shut off one breaker at a time to see if there is something in one of your rooms causing the problem. But having the hum with the volume turned down I'm with Norm on the Caps filtering the transform or you could possibly have a bad transformer or a grounding problem with the transformer. Good Luck, George T

::John
::
:: Did you use 10 mf @ 450 volt replacement filter caps? Are the originals disconnected? Hum with volume down is usually power supply filtering.
::
::Norm
::
:::I have an old 4 tube cathederal Austin radio that is not listed anyplace. It uses an 80, a 47 and two 24's. I recapped it and changed out-of-tolerance resistors. It runs OK but still quite a bit of hum even when the volume control is way down. It is a TRF. Would it need alignment or how can I get rid of the hum?
:::
::
::
:Hi, you might have something in the house causing the set to hum, like a wall transformer or LED light. I have to turn on the hall light to get a clear signal on pretty much all of my radios. You can always shut off one breaker at a time to see if there is something in one of your rooms causing the problem. But having the hum with the volume turned down I'm with Norm on the Caps filtering the transform or you could possibly have a bad transformer or a grounding problem with the transformer. Good Luck, George T
:
Norm and George
Ya, I used two 10's at 450 and cut out the leads to the old can. A long time ago someone had put a 16ufd from pin 4 of the 80 to ground and it was open. I tried replacing it and noticed no difference with a good one or without it so left it out. With the volume up on a station you didn't notice the hum and this belonged to a friend so gave it back and he was happy. He wasn't going to play it much he said.

:I have an old 4 tube cathederal Austin radio that is not listed anyplace. It uses an 80, a 47 and two 24's. I recapped it and changed out-of-tolerance resistors. It runs OK but still quite a bit of hum even when the volume control is way down. It is a TRF. Would it need alignment or how can I get rid of the hum?
:

The alignment, such as it is, on this set would have nothing to do with hum. Presumably you do not have a schematic for the radio. So, look underneath the chassis and see if the center tap of the B+ winding on the power transformer goes to a resistor stack instead of being soldered directly to chassis ground. (This resistor stack is used to generate a negative voltage to bias the grids.) If it does go to a resistor, look for an electrolytic capacitor hanging off of a "downstream" resistor in the stack. The negative side of the cap should go to this node, NOT GROUND, and its positive side should go to ground. This is somewhat counterintuitive, but makes sense once you understand that chassis ground is at a higher positive voltage than the negative grid supply node. It's pretty common to find that this cap has been installed in reverse polarity when someone recapped the set, particularly if they didn't have a schematic to guide them. The tendency is to assume that the negative side of all electrolytics must go to chassis ground. If this cap is misinstalled, it will inject unfiltered full-wave rectified DC onto the grids and you will hear 120 Hz hum. The capacitor smooths this pulsating DC on the bias node and reduces the hum.