The sound on my Detrola Model 302 sounds like when you try to talk underwater. I have recapped the set and changed tubes. I think it is an audio output problem but can find nothing wrong. Can the speaker cause this and, if so, what can I do? Is the field coil doing this?

I don't feel the field coil can do that.
It only creates an electro-magnet for the speaker to operate with.

Did the radio ever or recently ever play well?

:I don't feel the field coil can do that.
:It only creates an electro-magnet for the speaker to operate with.
:
:Did the radio ever or recently ever play well?

I agree with Peter about the field coil. Does the volume control setting improve or detract from the sound quality? Strong or weak station? Need more information.
Lewis

The field coil most likely won't cause the problem but the speaker voice coil may be rubbing the core and or may be out of alignment. Try connecting another speaker across the voice coil connections. If the voice coil is out of alignment you can loosen the spider and place shims (I use film negatives) in between the voice coil and the core and then re-tighten the spider. Sometimes the glue lets loose on the outer rim of the speaker. This can also be re-aligned and re-glued.

MRO

::I don't feel the field coil can do that.
::It only creates an electro-magnet for the speaker to operate with.
::
::Did the radio ever or recently ever play well?
:
:
:
:I agree with Peter about the field coil. Does the volume control setting improve or detract from the sound quality? Strong or weak station? Need more information.
:Lewis
:
:
:

You didn't say what kind of radio this is, but here are some general suggestions: garbled audio with hum is possibly caused by bad filter capacitors, though I assume that you replaced these.

Garbled audio can be due to a faulty rectifier, usually of the solid state kind, where leakage is beginning to occur. However, in such cases, major power supply components start to overheat and/or possibly blow apart when reverse leakage is severe enough to cause garbled audio. Selenium rectifiers are probably encountered the most in tube type equipment, though both selenium and silicon rectifiers can leak and/or short. Selenium is more prone to some leakage, and silicon is more prone to dead shorts.

Garbled audio either with or without hum can also be due to an audio or RF grid connection that is broken or loose (especially when a wire or capacitor is still connected to the grid, but has broken off of some other point....audio will usually be much quieter, though, and possibly nonexistant), or an audio grid bias resistor (or transformer return wire) that is broken or misconnected (say you connected it to the filament supply instead of B- or its appropriate bias point).

Bad audio bypass capacitors will cause garbled audio usually after 15 to 20 minutes of operation, though sometimes sooner. You say that you replaced capacitors, so the problem is most likely not there.

If the radio uses a loop antenna, and the return side of the loop is broken or disconnected, or connected to some alternating current source (filament supply instead of B- or AVC line), audio will be garbled. Make sure that the AVC resistor and capacitor are in good shape, and are connected properly. Having either connected to the filament supply will cause garbled audio, and might cause total radio silence, and having either one open might cause garbled audio if near alternating current sources (transformer or filament supply), though in my experience, when an AVC capacitor opens up, I get unwanted feedback and symptoms other than garbled audio.

If the loop antenna is disconnected all together, and a long wire antenna is used in its place, being connected either directly or through a capacitor to the 1st RF tube grid, garbled audio will result.

Unwanted feedback in the RF section can cause garbled audio, though this might also be accompanied by a high pitched tone or a rushing sound. Unwanted feedback can be caused by inadequate shielding, improper component connection, faulty component(s) (especially capacitors...such as the small value, say .1 MFD, capacitors that filter such things as RF screen grids and plates, where the grids and plates are fed B+ through a secondary series resistor). It can also be caused by improperly placed wires and/or components. Running speaker wires by RF or 1st audio tubes can cause feedback.

Garbled audio can be caused by placing a floating ground chassis of an AC/DC radio on a grounded or semi-grounded surface, especially if the cord is plugged in so that the chassis is hot while the radio is running. This can also occur with some AC-only radios.

A cathode to heater short in a tube might cause garbled audio, but will also most likely cause hum. If you cleaned the tubes in water and didn't let them dry properly, water in the bakelite bases (if bakelite base type tubes are employed) will cause any number of problems, including garbled audio, hum, poor operation, arcing, and possible absence of any signal at all.

One rather strange problem I had a long time ago has led me to not use WD-40 for cleaning my volume controls anymore. Instead I now wipe a thin layer of di-electric grease on the resistance material inside of the control. What happened was that I had (and still have) a Zenith portable 5-G-500 with a floating chassis, and one of those metal encased filament dropping resistors with the multiple taps. The volume control started to leak to the chassis after I sprayed it with WD-40, and carbon granules worked their way into the WD-40, forming a leakage path from the control parts to the shell, and thence to the chassis. The filament resistor also developed its own leak from heat and age. At certain points on the volume control, the audio would drop out and act really funny. A rushing sound would occur. I was finding 60 volts DC on the chassis. I finally found the trouble to be from the filament dropping resistor. However, after I repaired the resistor, the volume control would still sound garbled at certain volume levels. I measured between the control parts and the casing, and found leakage. After correcting the leakage (cleaning and then coating carbon with di-electric grease), troubles went away. I also had a similar problem with my DeWald television when I sprayed the vertical control with WD-40. Though it didn't result in garbled audio, vertical control was impossible. I cleaned the control and then used di-electric grease on the carbon. The vertical roll control is now very easy to adjust.

T.

YES...This is a small old Detrola Model 302 W/clock and you were right on TD. Thanks so much, when you said theloop might not be connected that was it, Thanks again.

:You didn't say what kind of radio this is, but here are some general suggestions: garbled audio with hum is possibly caused by bad filter capacitors, though I assume that you replaced these.
:
:Garbled audio can be due to a faulty rectifier, usually of the solid state kind, where leakage is beginning to occur. However, in such cases, major power supply components start to overheat and/or possibly blow apart when reverse leakage is severe enough to cause garbled audio. Selenium rectifiers are probably encountered the most in tube type equipment, though both selenium and silicon rectifiers can leak and/or short. Selenium is more prone to some leakage, and silicon is more prone to dead shorts.
:
:Garbled audio either with or without hum can also be due to an audio or RF grid connection that is broken or loose (especially when a wire or capacitor is still connected to the grid, but has broken off of some other point....audio will usually be much quieter, though, and possibly nonexistant), or an audio grid bias resistor (or transformer return wire) that is broken or misconnected (say you connected it to the filament supply instead of B- or its appropriate bias point).
:
:Bad audio bypass capacitors will cause garbled audio usually after 15 to 20 minutes of operation, though sometimes sooner. You say that you replaced capacitors, so the problem is most likely not there.
:
:If the radio uses a loop antenna, and the return side of the loop is broken or disconnected, or connected to some alternating current source (filament supply instead of B- or AVC line), audio will be garbled. Make sure that the AVC resistor and capacitor are in good shape, and are connected properly. Having either connected to the filament supply will cause garbled audio, and might cause total radio silence, and having either one open might cause garbled audio if near alternating current sources (transformer or filament supply), though in my experience, when an AVC capacitor opens up, I get unwanted feedback and symptoms other than garbled audio.
:
:If the loop antenna is disconnected all together, and a long wire antenna is used in its place, being connected either directly or through a capacitor to the 1st RF tube grid, garbled audio will result.
:
:Unwanted feedback in the RF section can cause garbled audio, though this might also be accompanied by a high pitched tone or a rushing sound. Unwanted feedback can be caused by inadequate shielding, improper component connection, faulty component(s) (especially capacitors...such as the small value, say .1 MFD, capacitors that filter such things as RF screen grids and plates, where the grids and plates are fed B+ through a secondary series resistor). It can also be caused by improperly placed wires and/or components. Running speaker wires by RF or 1st audio tubes can cause feedback.
:
:Garbled audio can be caused by placing a floating ground chassis of an AC/DC radio on a grounded or semi-grounded surface, especially if the cord is plugged in so that the chassis is hot while the radio is running. This can also occur with some AC-only radios.
:
:A cathode to heater short in a tube might cause garbled audio, but will also most likely cause hum. If you cleaned the tubes in water and didn't let them dry properly, water in the bakelite bases (if bakelite base type tubes are employed) will cause any number of problems, including garbled audio, hum, poor operation, arcing, and possible absence of any signal at all.
:
:One rather strange problem I had a long time ago has led me to not use WD-40 for cleaning my volume controls anymore. Instead I now wipe a thin layer of di-electric grease on the resistance material inside of the control. What happened was that I had (and still have) a Zenith portable 5-G-500 with a floating chassis, and one of those metal encased filament dropping resistors with the multiple taps. The volume control started to leak to the chassis after I sprayed it with WD-40, and carbon granules worked their way into the WD-40, forming a leakage path from the control parts to the shell, and thence to the chassis. The filament resistor also developed its own leak from heat and age. At certain points on the volume control, the audio would drop out and act really funny. A rushing sound would occur. I was finding 60 volts DC on the chassis. I finally found the trouble to be from the filament dropping resistor. However, after I repaired the resistor, the volume control would still sound garbled at certain volume levels. I measured between the control parts and the casing, and found leakage. After correcting the leakage (cleaning and then coating carbon with di-electric grease), troubles went away. I also had a similar problem with my DeWald television when I sprayed the vertical control with WD-40. Though it didn't result in garbled audio, vertical control was impossible. I cleaned the control and then used di-electric grease on the carbon. The vertical roll control is now very easy to adjust.
:
:T.

:The field coil most likely won't cause the problem but the speaker voice coil may be rubbing the core and or may be out of alignment. Try connecting another speaker across the voice coil connections. If the voice coil is out of alignment you can loosen the spider and place shims (I use film negatives) in between the voice coil and the core and then re-tighten the spider. Sometimes the glue lets loose on the outer rim of the speaker. This can also be re-aligned and re-glued.
:
:MRO

If you would "split" the radio at the volume control (unsolder the hot side of the control, that is the wire at the loud setting) and either insert a signal from a CD player or something like that, or listen to the radio half of the receiver with another amplifier, you will know which half the trouble is in.

Lewis