I am new to restoring old radios and have learned a lot about them over the past few months. I have a philco 41-280. When I bought it the only thing it would do is light the tubes. I have since replaced all the capacitors and now it will hum and crackle but still no other sound. Could someone tell me what I should check next. I would appreciate it .

:I am new to restoring old radios and have learned a lot about them over the past few months. I have a philco 41-280. When I bought it the only thing it would do is light the tubes. I have since replaced all the capacitors and now it will hum and crackle but still no other sound. Could someone tell me what I should check next. I would appreciate it .

Hi Alan,

If there is some hum, then possibly the audio tubes are working. Use a screwdriver blade and touch the center terminal of the volume control. This should cause a fairly loud hum in the speaker. One more thing to check is to see if the loop antenna is in the cabinet. The loop consists of two heavy wires shaped in a square configuration separated by insulated spacers. There are three wires from it which go to the screw terminal strip on the left rear of the chassis. The first on the left of this strip is not used. If the loop is in the cabinet, make sure the wires from the loop go to the proper terminals. If I remember correctly the loop has a jumper wire that connects the two loops together. This wire (white?)would go to terminal 3 and one of the other two wires (red?) goes to terminal 2 and the other (blue?)to terminal 4. The reason I mention this is I was given a 41-280 several year ago and was missing the antenna loop. The radio would not work. I eventually found the loop for it and then the radio would work. One other thing to do is double check your capacitor replacement in the power supply. The electrolytic whose plus lead connects to the 84 tube cathode is not grounded to the chassis but goes to the center tap on the high voltage winding of the power transformer.

Radiodoc

::I am new to restoring old radios and have learned a lot about them over the past few months. I have a philco 41-280. When I bought it the only thing it would do is light the tubes. I have since replaced all the capacitors and now it will hum and crackle but still no other sound. Could someone tell me what I should check next. I would appreciate it .
:
:Hi Alan,
:
:If there is some hum, then possibly the audio tubes are working. Use a screwdriver blade and touch the center terminal of the volume control. This should cause a fairly loud hum in the speaker. One more thing to check is to see if the loop antenna is in the cabinet. The loop consists of two heavy wires shaped in a square configuration separated by insulated spacers. There are three wires from it which go to the screw terminal strip on the left rear of the chassis. The first on the left of this strip is not used. If the loop is in the cabinet, make sure the wires from the loop go to the proper terminals. If I remember correctly the loop has a jumper wire that connects the two loops together. This wire (white?)would go to terminal 3 and one of the other two wires (red?) goes to terminal 2 and the other (blue?)to terminal 4. The reason I mention this is I was given a 41-280 several year ago and was missing the antenna loop. The radio would not work. I eventually found the loop for it and then the radio would work. One other thing to do is double check your capacitor replacement in the power supply. The electrolytic whose plus lead connects to the 84 tube cathode is not grounded to the chassis but goes to the center tap on the high voltage winding of the power transformer.
:
:Radiodoc
:
Radiodoc,
I appreciate your reply. I put the screwdriver blade on the center terminal of the volume control and the hum gets louder. I do have the antenna loop but it was not hooked up to the radio when I got it. I thank you for letting me know which wire goes where with the antenna. I have tried hooking the antenna up but I still just have a hum.
You told me to double check the capacitor replacement in the power supply. I have 2 electolytics. I believe I have them right as well but still I just have a hum.
Could it be a tube? I replaced one of them. I do not have a tube tester to check the others.
I sure do appreciate your help!!
Alan

:::I am new to restoring old radios and have learned a lot about them over the past few months. I have a philco 41-280. When I bought it the only thing it would do is light the tubes. I have since replaced all the capacitors and now it will hum and crackle but still no other sound. Could someone tell me what I should check next. I would appreciate it .
::
::Hi Alan,
::
::If there is some hum, then possibly the audio tubes are working. Use a screwdriver blade and touch the center terminal of the volume control. This should cause a fairly loud hum in the speaker. One more thing to check is to see if the loop antenna is in the cabinet. The loop consists of two heavy wires shaped in a square configuration separated by insulated spacers. There are three wires from it which go to the screw terminal strip on the left rear of the chassis. The first on the left of this strip is not used. If the loop is in the cabinet, make sure the wires from the loop go to the proper terminals. If I remember correctly the loop has a jumper wire that connects the two loops together. This wire (white?)would go to terminal 3 and one of the other two wires (red?) goes to terminal 2 and the other (blue?)to terminal 4. The reason I mention this is I was given a 41-280 several year ago and was missing the antenna loop. The radio would not work. I eventually found the loop for it and then the radio would work. One other thing to do is double check your capacitor replacement in the power supply. The electrolytic whose plus lead connects to the 84 tube cathode is not grounded to the chassis but goes to the center tap on the high voltage winding of the power transformer.
::
::Radiodoc
::
:Radiodoc,
:I appreciate your reply. I put the screwdriver blade on the center terminal of the volume control and the hum gets louder. I do have the antenna loop but it was not hooked up to the radio when I got it. I thank you for letting me know which wire goes where with the antenna. I have tried hooking the antenna up but I still just have a hum.
:You told me to double check the capacitor replacement in the power supply. I have 2 electolytics. I believe I have them right as well but still I just have a hum.
:Could it be a tube? I replaced one of them. I do not have a tube tester to check the others.
:I sure do appreciate your help!!
:Alan

Hi Alan,

There can be a number of things that keeps a radio from working. We know that the audio works now even though there is hum. Does the hum increase when turning up the volume? If there is not much change then the hum problem is probably in the power supply. Since the audio circuits are working a down-n-dirty check you can make is to rock or remove each tube starting with the 2nd IF 7B7 tube and listen for a click or noise in the speaker. If you have a click then go to the 1st IF 7B7 and do the same. If, say, you find there was not a click or noise when you pulled the 1st IF tube then the first IF transformer would need to be checked for continuity. Make sure the pins on the tubes are clean (I personally hate loctal tubes). Don't forget to check the value of resistors including those in the power supply. You mentioned two electrolytic caps in the power supply. There is an 8MFD electrolytic with an 18,000 Ohm and a 33,000 Ohm resistor connected to it. If this is shorted will keep the 1st detector and oscillator tubes from working.

Radiodoc

We have an original cabinet my husband's grandfather bought, interested? Thanks, Bonnie

::I am new to restoring old radios and have learned a lot about them over the past few months. I have a philco 41-280. When I bought it the only thing it would do is light the tubes. I have since replaced all the capacitors and now it will hum and crackle but still no other sound. Could someone tell me what I should check next. I would appreciate it .
:
:Hi Alan,
:
:If there is some hum, then possibly the audio tubes are working. Use a screwdriver blade and touch the center terminal of the volume control. This should cause a fairly loud hum in the speaker. One more thing to check is to see if the loop antenna is in the cabinet. The loop consists of two heavy wires shaped in a square configuration separated by insulated spacers. There are three wires from it which go to the screw terminal strip on the left rear of the chassis. The first on the left of this strip is not used. If the loop is in the cabinet, make sure the wires from the loop go to the proper terminals. If I remember correctly the loop has a jumper wire that connects the two loops together. This wire (white?)would go to terminal 3 and one of the other two wires (red?) goes to terminal 2 and the other (blue?)to terminal 4. The reason I mention this is I was given a 41-280 several year ago and was missing the antenna loop. The radio would not work. I eventually found the loop for it and then the radio would work. One other thing to do is double check your capacitor replacement in the power supply. The electrolytic whose plus lead connects to the 84 tube cathode is not grounded to the chassis but goes to the center tap on the high voltage winding of the power transformer.
:
:Radiodoc
:

ALso, aside from resistors, which is a key point to check, check coils. Check IF transformers. They should have continuity, but shouldn't have zero ohms. If they do, then the trimmers (or fixed capacitors if trimmer capacitors aren't used) are shorted.

Thomas