[bobclausen]

https://radio.codegods.ca/sites/default/...west37.jpg

I’m working on a Westinghouse 813X. I’ve replaced all the caps, replaced all the old rubber wire, updated all the resistors and tubes. The voltages are a bit higher but well within reasonable. 

The radio does work but the volume is problematic. When I turn the volume control all the way, the radio goes quiet. if I attach a wire from the antenna lug to the grid cap of the 6L7 tube, the radio’s volume is good. Turn the volume up again and it goes silent. 

Just hoping someone can provide some advice as to where I should start troubleshooting. I do have a spare volume control but have not tried it on the radio yet. Is that where I should start troubleshooting and what causes the increase in volume when that wire is attached?

I appreciate any and all suggestions.

[Arran]

First I would double check your work, as a bulk recap, rewire, and re-resistor job is fraught with possibility for anything from something being wired to the wrong terminal, to a wire left off, to a missed solder joint. This is why I encourage people to perform a test power up if possible, to establish a base line. After that it's best practice to start from one end of a set, and work your way to the next, whilst recapping, rewiring, etc, and if possible to test the set in-between moving on to the next step, to see if there is an improvement, or if it still works.
When you mention "updating" the tubes, do you mean that you replaced them all? I have found that it is very rare for every tube in a set to need replacement, aside from a battery set. Even in the case of an individual tube unless it's shorted, gassy, or burned out, the radio will still work unless it has very weak emission. With the replacement tubes have they been tested? Do you know that they are all good?
Have you checked the coils? Is there continuity across the primary of the antenna coil? Have the grid cap leads been replaced? How are the solder joints on the clip, and the other end? That is a weak point on double ended tubes and can cause a lot of headaches, like volume drops, etc.
With regard to the volume pot, is it a replacement? Is it a linear or a log pot? What resistance is it? If it's giving trouble I would examine the solder joints on the terminals, and also make sure it's wired the right way around. I would also give it a cleaning with some alcohol spray.
Regards
Arran

[bobclausen]

Hi Arran

What I meant by updating tubes was to replace the 5w4 that tested dead and put in a 6J7 that was missing. All the others tested ok. Two of the grid cap wires were replaced because they were falling apart. I cleaned up the caps as best I could with a small wire brush.

I don't know if the volume pot is original and sorry I don’t know the difference between a linear or log pot. It reads 1.9 Megs from lug1 to lug3.

I did use F5 on the pots and D5 on the switches.

I did have to change the output transformer. The original was dead. I had Philco 32-7027N that I installed. I looked at all the Philco catalogs and could not find a reference to that particular transformer. I believe it’s probably a Canadian model. I don’t know if that could be a problem.

[MrFixr55]

Hi Bob,

What happens if you turn the volume control down and back up slowly after losing sound? Do you have to turn the set off after the issue occurs before sound is restored? What does the tuning eye do? The tuning eye should NOT change when raising or lowering the volume. If it returns to normal until you reach a certain level, you may be saturating the Audio stage.

In addition, an intermittent speaker connection can cause this. the flexible braided wires between the speaker's voice coils and the terminals of the speaker experience much flexing and break. Resolder these.

In old days, turning the volume control high would saturate the RF Stage, as the Volume control controlled either antenna signal strength, RF stage bias or both. This happened often with older sets that did not have AVC but most superhets made 1934 or later, including yours have AVC, and the volume control merely controls signal level to the 1st Audio stage, and varying the volume control shouldn't change the gain of the RF, converter or IF stages, only the audio stage. This is why checking the tuning eye function can help determine if the problem is in the audio stages (likely) or in the RF, converter, IF and detector stages (unlikely). If there is no sound, and turning the tuning cap causes the tuning eye varies but no sound is generated, this can rule out the RF, converter, IF and detector stages.

There is a lot of resistance between the low end of the volume pot and ground, particularly in R14, a 470K resistor. This is quite a bit more than in other sets.

Verify the resistance of resistors R13 (the volume control), R 14 and Resistors R21, 22 and 23. Also verify the condition of capacitor C27. this capacitor may be metal cased to be shielded and you may not have changed it. If thi capacitor is leaky, increasing the volume could saturate the 1st AF tube. Saturation does not mean that maximum volume will be attained, saturation will "rail" the voltage output of the tube, there will be no variation, therefore no sound.

High resistance potentiometers are generally rated as either Linear taper or Audio taper. having a linear taper won't cause this issue but will cause difficulty in controlling volume, especially at low levels.

The trouble may be elsewhere, such as a bad 1st AF, bad output, bad speaker voice coil flex leads, etc. but start there.

Hope this helps!

[Arran]

I had forgotten about that, Canadian Westinghouse used to like encasing audio coupling caps inside of a metal shield screwed to the chassis, they also liked to use shielded cable to connect them, and the volume control. It is easy to miss them during a bulk recap, someone did this in my Westinghouse 780A, twice!!
One way to spot if the volume control was a replacement is if the shaft of the control is noticeably different, most of the others will be made out of brass with a half shaft, not aluminum, and no splines like many replacements seem to have. Some volume controls will also have an extra terminal, with a resistor connected to it, most Westinghouse sets from this era did, an incorrect replacement would not.
An incorrect audio output transformer can cause issues, but not intermittent ones, and they have no connection to the volume control pop. If the Philco transformer came from a set with a similar audio output tube then it should work fine, such as if the set had a #42 and the Westinghouse has a 6F6, if it came from a set with a #41 or a 6K6 then it will work but is a mismatch and the set will sound odd.
Regards
Arran

[MrFixr55]

My RCA T7-5 has the same type of cap. It's the only one I have not replaced. However, my set functions just fine.