[TheUniversalDave1]

I took it apart, blew all the dust out and grabbed the Naval Jelly. I also got some GOJO Creme Hand Cleaner and started cleaning the cabinet. I say it did excellent at getting all the crap off the veneer. I put Naval Jelly all over the chassis to get the rust off and otherwise clean it. Somebody replaced the 84 Rectifier with a 5Y3 along with the whole transformer. I hope that won't be a problem - it would not be easy sorting through some radio repair guy's handiwork. The electrolytics will need to be replaced - they are oozing some chalky white stuff. Does anyone have any tips for that? I will be ordering new push buttons and rubber feet from Renovated Radios as soon as possible.

[TheUniversalDave1]

Here is the chassis covered in Naval Jelly.

[TheUniversalDave1]

So I took a three week hiatus, but that's okay because the 39-30 works now. I took it into the AHRS today and we got rid of the 60 Hz hum. We put in 3 new electrolytic capacitors. But there is still a problem. It worked absolutely great on the AHRS building's antenna, but when I got home, the stations are very weak, but they're there. There is also an ever present scratchiness in the sound.

[Radioroslyn]

So what sort of ant do you have at home? Poor audio quality may be traced to leaky paper caps in the audio stages. Or a bad volume control.
Terry

[TheUniversalDave1]

Here is the makeshift antenna.

[Nick3092]

Is that 300 ohm twin lead connected to both the antenna and ground terminal? And it looks like you have a wire nut on the other end connecting them both? I wouldn't do that.

Just put a single wire on the antenna terminal only. 10' or so will work.

[Radioroslyn]

Nick is right. What you have there looks like to the radio is a big long skinny capacitor. Generally speaking an BC frequencies the longer and higher (like up in the trees) the better. The slingshot is your friend. 10' isn't much of at antenna as things go. Some sets have a scale measured it meters like 200-500m. That how long your ant would need to be to be resonant at the BC band. That's 500 mtrs long at the low end of the BC band. 50 or 100' is good and away from power lines. With something like that your be able to pickup all over the states at night. We are coming into the Summer months and propagation will be down a bit and static will be up. Conditions get better in the Fall though Spring.
Terry

[TheUniversalDave1]

Nick, I thought AM radio antennas had to be a loop?

[TheUniversalDave1]

Well what do you know! That solved the problem. I clipped a whole bunch of gator wires together and hooked it up to the drop ceiling grid, and reception is excellent! I turned off the fluorescent lights, and that solved the static problem too!

[Nick3092]

Most radios into the early 40's were designed as long wire radios, meaning no loop. Typically if a radio schematic shows just an antenna terminal on the schematic or shows an upside down triangle, that usually means it's a long wire. Most transformer sets are long wire, but some larger consoles were designed to have a built in loop (like the 40-180).

Most sets designed to use a loop will have a spiral square on the schematic indicating the loop antenna. It's also important to know that the loop was tuned for that particular radio. Meaning a loop from one radio may perform badly on another. Most often these are AC/DC transformerless sets. But not always.

[TheUniversalDave1]

We're not out of the woods quite yet, though. I let the radio play for about 30 minutes, and when I went back into the room after breakfast, I was met with a very powerful smell. Burning plastic or something. It was still playing fine, but the whole room reeked of that burning smell

[Nick3092]

You said you replaced the 3 electrolytic caps. Did you replace all the paper and wax caps? You should also check all resistors to make sure they are in spec. Personally, I replace them all while I'm replacing the caps. Cheap insurance, and I only want to dive into a set once.

Also, this radio is chalked full of rubber coated wire that is now crumbling off and could cause shorts. That should all be replaced or repaired (lifting one end and sliding heat shrink over it).

These things should all be done before playing the radio any more.

I actually just picked one of these up last week. And I can tell you to do the work properly around the band switch is going to be a little tricky. It may even require removing the switch. Not sure yet. I'll be ordering parts this week and hope to get to it in the next couple weeks.

[sam]

hey dave
like terry stated did you change all paper caps and electrolytic caps
you didn`t re stuff can. but did you mount new caps to connectors on bottom of can?
sam

[Radioroslyn]

Loop antennas in the back of a radio are a compromise made so folks would have a bunch of wires hanging around out of the back of there sets. Set will always work better will a long wire ant high up in the air. Now some folks well build large loop antennas which are very directional. They can be used to null out interfering signals or direction finding.
Terry

[Eliot Ness]

We're not out of the woods quite yet, though. I let the radio play for about 30 minutes, and when I went back into the room after breakfast, I was met with a very powerful smell. Burning plastic or something. It was still playing fine, but the whole room reeked of that burning smell

Like the others have said about the caps and resistors.  Also look for signs of overheating like discolored components and tar oozing out of power transformer (under chassis), etc.  Sometimes your nose is pretty good about localizing the smell (power off please!), other times it will be hard to narrow down after the odor dissipates.  Good luck!