[Nick3092]

Well, I finished up the recap, rewiring, and reresistoring and fired it up. It works. But does it ever have a loud hum to it. Worse than I ever heard on any AM radio before. The radio did work when I bought it from the guy, and this hum was not present. So I know it had to have been something I did wrong. Any suggestions on what to look at first?

[marty]

Hi All;
Check Your wiring ..
THANK YOU Marty

[Arran]

I think I know what may have happened, you may have miswired the negative end of one of the filter capacitors, probably the input filter capacitor coming off the rectifier tube and ahead of the field coil (filter choke) of the speaker. In many pre war radios the input filter capacitor has a floating negative end that is connected directly to the center tap of the power transformer, the output filter cap is connected to the chassis, and there is a large wire would resistor or series of resistors between the two capacitors on the negative side. I could go into a long explanation of why they did this but the simple answer is that they wired the power supply this way to provide negative bias for the tubes.
Regards
Arran

[Nick3092]

I did have the 12uf tied to the wrong spot. I knew it came off the double terminal strip, and I just instinctively tied the negative side of the cap to the terminal that was true ground. I moved it to the other (correct) terminal, and now it sounds great. This is a very nice sounding radio.

Thanks for the help!

Now I have one more question. I noticed on the antenna drum, 2 of the 5 wires are rubber coated, and one is in pretty bad shape. It looks like all you have to do open it up is pry up some staples. But putting them back in might be an issue. I would assume I could use a standard staple gun with the same size staples. How much trouble am I asking for if I open this up? Or should I just wrap the wires with electrical tape and call it a day?

[marty]

Hi All;
I would suggest Heat Shrink tubing instead of Electrial Tape.. I don't know enough about opening it up, so I can't say..
THANK YOU Marty

[Nick3092]

I decided to peek in the drum, and see how hard it would be to replace the wires. It turns out it's very easy. All you have to do is take out the staples around the top and the bottom. Leave the ones along the seam in place. Then unsolder the wire on the metal tab, and carefully slide the drum off.

It's basically a big X inside with wire wrapped around it and tapped in a few places. There is also a capacitor and resistor in parallel in there on the white wire that runs to the antenna terminal on the radio. I didn't notice them on the schematic at first.

I desoldered the terminals, cut new wire to the same length, and soldered them back on the new wire. Replaced the cap and resistor as long as I was in there. Slid the cardboard back on, re-stapled it around the top and bottom, and it's good to go again.

I attached a picture in case anyone wanted to know what it looks like.

[Electrothaumaturgist]

Excellent work!!! Did you notice any difference in the reception with the new cap and resistor installed in the antenna circuit, as opposed to with the old?

[Nick3092]

Not that I noticed. I checked the resistor after I replaced it. It was in spec. The cap was a micamold, and in my mind is always suspect. However, I don't have a reliable cap value tester or ESR meter.

[Nick3092]

Two other random questions. Speaking of mocamolds, I've read how to read the 3 dot color code. It's basically the same as a resistor. First number, second number, multiplier. But in this radio, in two places there was a 250pf cap according to the schematic. The actual caps were green-orange-green. Which I read as 5-3-100,000, or 5,300,000pf. What am I missing here?

Second question is inside the side pockets of my cabinet were 2 long U shaped brackets. They are as long as the chassis is deep. Are these supposed to go between the chassis bolt washers and the bottom of the shelf? Or did I just acquire some extra parts?

[Mondial]

Philco had their own color code for mica caps. Here is a link to Chuck's site for a table of codes vs. actual values:


http://www.philcorepairbench.com/micacap.htm

By the way, the problem with micamold caps only applied to later paper caps which were made in a case similar to those used for micas. These paper caps have the same problems typical of all other paper caps of the same vintage.

There has never been a reliability problem with actual mica caps made by micamold, but because of the confusion with the later paper types, all micamolds seem to have gotten a bad reputation.

[Ron Ramirez]

Second question is inside the side pockets of my cabinet were 2 long U shaped brackets. They are as long as the chassis is deep. Are these supposed to go between the chassis bolt washers and the bottom of the shelf?

Yes.

[Nick3092]

Not sure if anyone else ran into this, but I ordered new buttons from Renovated Radios, as mine were pretty much wrecked like every other Philco I've seen. And 2 or 3 of the 8 were nice tight fits on the shafts. But the others are a much looser fit. So when I change to a new preset, if it's a loose one, the previously selected button juts out past all the others. Any tricks to tightening up the fit of the buttons, or am I stuck with that behavior? Yeah, I know. Of all the problems I could have with this set, this is my complaint. But I'm kind of OCD that way. I want my buttons all nice and orderly.

[BrendaAnnD]

A toothpick (one of the flat kind) or a piece of matchbook paper between the shaft and button.