1970ish Zenith radio volume problem.

4/1/2009 1:36:52 PMradio joe

I have an amazing performing and sounding 1970ish Zenith table top model S-42505. The problem is I cannot adjust the volume on it. It stays pretty constant at a little bit above a normal level. I can adjust the the tone and "loudness" but not the volume. Now here is the thing. I cleaned all pots with cleaner. I checked associated volume resistors and capacitors and they test well. This radio has a 19T8 tube that is connected in some way with the volume control. The schematic for this radio is not on this web site but I did find a radio almost exactly alike in layout and tubes. That schematic shows the volume going through 19T8. The 19T8 tube I have tests bad in my heathkit tube tester but the radio still performs great. My first question is does this radio have a volume control? The two part Knob is labeled Off, Tone, Loudness. Is loudness volume? The other knob is Am or FM. My second question is my testing bad 19T8 tube the culprit with my non adjusting volume problem? I hate throughing parts at a radio. I believe the tube is the problem but don't have a spare to try it. Or, the radio just doesn't have a volume control to begin with. Thank you for your time and help. -radio Joe

4/1/2009 8:10:23 PMLewis L

:I have an amazing performing and sounding 1970ish Zenith table top model S-42505. The problem is I cannot adjust the volume on it. It stays pretty constant at a little bit above a normal level. I can adjust the the tone and "loudness" but not the volume. Now here is the thing. I cleaned all pots with cleaner. I checked associated volume resistors and capacitors and they test well. This radio has a 19T8 tube that is connected in some way with the volume control. The schematic for this radio is not on this web site but I did find a radio almost exactly alike in layout and tubes. That schematic shows the volume going through 19T8. The 19T8 tube I have tests bad in my heathkit tube tester but the radio still performs great. My first question is does this radio have a volume control? The two part Knob is labeled Off, Tone, Loudness. Is loudness volume? The other knob is Am or FM. My second question is my testing bad 19T8 tube the culprit with my non adjusting volume problem? I hate throughing parts at a radio. I believe the tube is the problem but don't have a spare to try it. Or, the radio just doesn't have a volume control to begin with. Thank you for your time and help. -radio Joe

Volume controls the audio output of the radio. Loudness does the same, but adds bass at low levels to compensate with the ear's poorer response to bass notes at lower levels.
Lewis

4/1/2009 9:11:19 PMEdd

And will yours also be having the sagging grille cloth ?

Its typical. . . particularly if rug rats have been around poking their fingers into it.

A sprayer wetting and dry out will typically shrink it a bit back to the norm.

Before we get onto the schematic aspect, lets physically see that the left cluster of two knobs on the front is the
AYE-EMM selector switch while the clear outer rear knob is the tuning. . . . thats a given. . . . right ?

NOW, on the right we have the concentrically arranged and clustered volume and tone control knob.

Any chance of any binding of the the two ?
You might have to confirm that by the holding in position of one of the two, while fully rotating the other thru its
270 degree range. Then swap and hold the other and rotate the same manner. DID the vol-you- me change, or
at the least; the tone control changed the sound ?

(Seems like I certainly remember the tone control as being the center knob on the unit.)

The last thought is that the outer knob has two small keying slots associated with engaging into the outer shaft.

Pull off the knobs and see if there is any possibility of them being “wallered” out such that a mechanical
engagement is not being accomplished ‘twixt the knob and the shaft.

As TONY the Tiger sezzz, that ray-dee-oo DOES have one G R E E E E E E E E E A T sound !

73's de Edd

ZEE_NUTS_Model S-42505 . . . . . Cabinetry :

4/2/2009 12:11:56 AMThomas Dermody

Loudness is volume. Check to see that the low end of the volume control is making continuity to the rest of the control. Otherwise the radio will stay pretty much at full volume regardless of where the control is set.

....As well as what Edd suggested.

4/9/2009 11:10:37 AMRadio Joe

I fixed it. Thank you everyone for your help. It was a bad 19T8 tube. Everytime I would put the chassis back in the case the volume would not work. The magnet of the speaker, which is mounted in the case, would mess with the tube next to it, 19T8. I swapped out the tube and it works great. Thank you everyone. Joe