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42-395 low sensitivity, distortion issues - Printable Version

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42-395 low sensitivity, distortion issues - dspy - 03-30-2026

Recapped and aligned chassis can receive the 2 local stations with little else across the dial and even the local audio is somewhat distorted, can't be tuned clear. I left those few  micamold type caps alone.  Replaced the bad audio output transformer. Still improving my alignment skills but it seemed to have aligned ok. The loctal sockets have about all had that thin crumbly insulator fail but otherwise seem to have good connection. Any thoughts on what else to check? https://philcoradio.com/library/download/service%20info/yearbooks/1942/split/Part27-Philco%201942%20RMS%20Year%20Book.pdf

RE: 42-395 low sensitivity, distortion issues - radiorich - 03-30-2026

Hello dspy,
First of all, welcome to the forum! It sounds like you’ve gotten a great start on this set. Have you tested the tubes? Also, do you have any test equipment, like an audio signal tracer? That would be handy for figuring out if the issue is in the audio amplifier section or earlier.

Sincerely Richard

RE: 42-395 low sensitivity, distortion issues - morzh - 03-30-2026

What Rich said. I'd ask the same exact questions.

RE: 42-395 low sensitivity, distortion issues - dspy - 03-30-2026

Thanks for the warm welcome! I have checked and double checked the tubes and all test good now. I don't have a signal tracer but may be able to borrow one.

RE: 42-395 low sensitivity, distortion issues - morzh - 03-30-2026

What kind of tube tested do you have?

RE: 42-395 low sensitivity, distortion issues - dspy - 03-30-2026

I have a BK 707, the loctal tubes are in the emissions section. I have a backup Philco tester as well, but also emission.

RE: 42-395 low sensitivity, distortion issues - morzh - 03-30-2026

Well, that was what I was driving at.
You did not test them in the upper part, as loctals are tested for emission only.

You need to confirm good mutual conduction for all tubes.

RE: 42-395 low sensitivity, distortion issues - DaleHCook - 03-30-2026

morzh Wrote:  You need to confirm good mutual conduction for all tubes.

I will second that. Different tests, offered by different tube testers, have different uses. I use my emission tester (EICO 625) only for power tubes, where low emission can render a tube useless for producing power. For small-signal tubes I find my dynamic mutual conductance tester (Hickok 533) more useful. Bear in mind that no tube tester can tell you if a tube is good - it can only tell you that is is not definitely bad. Only the way that a tube behaves in the circuit where you are using it can tell you that it is good. Doing so may require specialized equipment (such as a quality oscilloscope or a laboratory grade signal generator) in the hands of an experienced restorer. That is why many of us have built up stocks of good used tubes.

RE: 42-395 low sensitivity, distortion issues - RodB - 03-30-2026

A set of mutually conducting tubes does wonders for radios.

RE: 42-395 low sensitivity, distortion issues - morzh - 03-30-2026

Forgot who said it (sometimes attributed to Chuck Yeager, but probably not):

- A good pilot can fly anything that flies - and, with some difficulty, even some things never meant to fly.


That is, any radio design will work with a set of mutually conductive tubes. How about duds with no emissions or even no filament continuity?

RE: 42-395 low sensitivity, distortion issues - dspy - 03-31-2026

ok, should have access to a signal tracer Wednesday, scratching my head on the mutual conductance tester.