[rps65619]

I just attempted my first radio restoration -- Philco Transitone 46-200.  Replaced capacitors and resistors.  Aligned by ear...  if that is even a thing.  I don't have a signal generator, etc.

I am pleased to report there was no smoke when I powered it up, and it works.  So that's a plus.  )

However, I do have a few concerns and questions.  Turning to the experts for help.

1)  Is it normal to have a very low/faint volume (I can hear the station tuned) even when the volume is all the way down?  In other words, it doesn't completely mute.  Not a big deal.  More of a curiosity.

2)  Why would I have a low hum when the volume is all the way down?  The hum is low enough that as the volume is turned up, it "drowns out" the hum.   I would like to eliminate the hum.

3)  Here's the biggest deal...   I have a problem with the tuning capacitor (I think).   It tunes well and picks up stations until I get down to about 650.  Then a scratchiness starts as I continue to turn the tuning knob down to 550.  The scratchiness sounds like something is touching electrically that shouldn't, and it always starts at exactly the same spot on the dial.  And, a very strong local station (560) won't pick up at all...   the tuner is deaf between 550-650, except for the scratchiness while I'm actually turning the knob.  The tuning capacitor looks clean.  I used air and a no-residue electrical cleaner.  

Thank you in advance.

Bob

[Radioroslyn]

1 could be a bad volume control but I'm betting on leakage between the diode and triode section of the det/1st audio tube. Would ignore it.
2 Lots of causes or it could just be inherent in the set.
3 Seem like you've got a bent plate on the tuning cap. Check the outside plates to see if they are rubbing on the plate next to it. If it is just bend it out a little.

[mikethedruid]

With the set turned OFF, attack an ohm meter across the tuning cap. Turn it through its full rotation, and note if the meter shows any change of resistance. Do this for each section. It sounds to me like one of the plates may be shorting to an adjacent one. In that case, some very slow and careful persuasion will be needed to bend it back to where it no longer shorts. There WILL be a resistance because the cap sections are connected across coils. If you want the clearest readings, unsolder the wire from the stator section before you measure it, but that is not really necessary. A short will show up either way. Often, careful observation is all that is needed to find it, not even an electrical check.

[rps65619]

Thanks, guys...  I was suspecting a bent plate too.   But wouldn't have thought of using an ohmmeter to check the tuning capacitor.  Learning so MUCH.

Thanks again.   Will update.

[462ron]

One trick that I have used successfully to find where a plate might be touching or shorting out will require you to disconnect any wires connected to the tuning gang. Charge up an electrolytic and connect it to the frame and the other lead to the stator. Then in a darkened room, rotate the tuner and if there is a short or some debris between the plates, there will be a spark, helping you to locate where exactly the problem is. Also, using this method, I've had the discharge of the electrolytic actually clear the problem, sometimes! YMMV

Ron

[rps65619]

You guys are so good.

One outside plate on the tuning condenser was bent and touching.

I couldn't see it without completely removing the tuning condenser from the chassis, but once I did it was easy to spot and fix.

Thank you so much for your help.   Radio now plays great, and tunes well throughout the entire AM band.

Bob