[Deathstryker]

Hello everyone. This is my first post here.

I've had a Philco 46-350 (a common model I hear) for about 10 years now and the other day I was looking at it and decided I was finally ready to restore it. 10 years ago, my grandpa gave this to me and I was just a teenage kid. Back then, I replaced the cord on it because the old one was cracked and I figured it would fix it. I was wrong. The thing still didn't turn on. Back then, I remember looking for resources on what would be wrong with it and how to fix it, however I remember the only thing I could find was a couple of websites that provided services on fixing radios so I decided to give up and shelve it.

Fast forward 10 years later...
The internet has WAY more resources for fixing radios now and I've decided to finally tackle this project again. I've read a lot of resources on fixing radios and found the schematic for my model and feel pretty confident about this project. I've decided to replace all of the non-electrolytic wax capacitors and the "can" electrolytic capacitor. I've already started to order supplies for it. Now, I've got a little bit of experience fixing antique fans but this is my first radio, thus I may have a few questions along the way. Thus my first question is this:

My "can" multi electrolytic capacitor looks like it exploded. The middle was blown out of it and looked like it was bulging outwards. What would cause it to do this? The reason I ask this is because I obviously don't want to put another one in there and have it explode again if it is caused by some issue other than the can itself.

Thanks,
-Josh

[John R]

Josh,
Electrolytic caps can 'explode' one their own without an external cause...seen many of these over the years. However, I would very carefully check the values of resistors R11, R3, R13 & R14 in the power supply section. Also, if you have access to a tube checker be sure the tubes are good and not shorted especially the rectifier tube and the audio output tube. The Nostalgia Air schematics gives a list of the resistances from the tube pinouts to ground. Check these out to see if they are close to the chart. Good luck.

[Deathstryker]

Thanks for your response, John.

I do not currently have a tube tester but I will check the resistors.

I've been thinking of buying one but I'm not sure which one to get or stay away from. Any suggestions?

[codefox1]

This is a really nice set, very sensitive and one of my vavorites. I have a couple of them. The tubes are really fragile, so you want to make sure you get the power supply in order before powering up the set.

You can visit nostalgia air for tube data and a schematic for your set. With a simple digital meter you can test the continuity of the filaments of your tubes to see if any are bad.

Chances are really good that if the filament is good and the glass is not broken, the tube is good. If the 117Z3 is bad, you can substitute a silicon diode and an additional 500 ohm or so series resistor to tame the power supply down. You need to protect the filament string at all costs.

The capacitors will all have to be changed. Every single one of 'em miss one, and it'll haunt you forever like one hiding inside the first IF Can did me ; and probably most if not all the resistors, and really they're cheap enough.

We're here if you have more questions

[Deathstryker]

Thanks for the info.

I checked some of the resistors.

On R3 (470) I get 660.
On R11 (900) I get 898.
On R13 (65) I get 62.1

I was unable to test R14 because my current OHM meter only has a 200 and 2K setting and this is a 120K resistor so I couldn't get a reading. I'll probably buy another one soon and check it.

As far as the tubes go, I got the PDF off of Nostalgia Air and I see the tubes list on the last page but I don't really understand which pins to check for continuity.

[codefox1]

Looking from the underside of the radio you count pins starting at the first pin to the left of the space or locating key and going clockwise.

You can get tube information from Nostalgia Air as well. There are a lot of inexpensive digital meters available, so inexpensive that it doesn't cause grief if you burn one up. But after burning up 3 or 4 of 'em, I bought one for around $30 that autoranges and tests diodes, capacitance, and I havent' destroyed it yet.

If you need a clearer copy of the schematic or service data, you can get one from Chuck, the co-moderator for a modest fee.

Anyway, in your set, the little tubes should show very low ohms between pins 1 and 7. The medium 117Z3 should show a few more ohms between pins 3 and 4. The 3Q5 should show continuity betwewen 7 and 8 and also between 8 and 2. It is not necessary to remove the tubes to do this test. If you do remove any tubes, label them because sometimes the numbers rub off. Unless you plan to take up the hobby, you can get a whole set of tubes for this radio for a whole lot less than even a modest tube tester in working condition.

In any case, all the paper capacitors in the set need to be replaced, not just the electrolytics. And you will find instances where resistors have drifted up beyond the 20% tolerance considered normal. As they only cost pennies, and most of the time you have to disconnect one end to get a reading, I usually just replace them. I usually order a few extras of the values that are needed time after time, and sometimes my stash is sufficient to do a job without suffering a shipping fee for just a couple of items.

One more thing with this set, unless you are considering cobbling together a battery pack you can remove that troublesome interlock switch that was used when you wanted to plug the power cord in. You'll see what I mean when you get into it.

[Deathstryker]

Got a more capable multimeter today.

R14 (120K) reads 132K

117Z3 (pins 3 and 4) reads .407K OHMS (If my math is correct, that is 407 OHMS)
1U5 (pins 1 and 7) reads 8.5 OHMS
1T4 (in the middle) (pins 1 and 7) reads 10.3 OHMS
1R5 (pins 1 and 7) reads 10.2 OHMS
1T4 (in the corner) (pins 1 and 7) reads infinite

3Q5 (pins 7 and 8 / 8 and 2) shows continuity.

Is there a recommended place to get capacitors and resistors all on one order so I don't have to get charged for shipping for each and every thing?

[codefox1]

Well, Justradios.com is a very hobbiest friendly family company, and they should have just about everything you need. Jamico, Mouser, and Digikey are also pretty reliable.

Test your 117Z3 filament out of circuit (like remove it.) If it's open you're going to replace it with a 1N007 diode and 220 ohm 10 watt resistor which will set you back about $2.00.

[Deathstryker]

I did test it out of the chassis. Pin 3 and 4 still give me that reading.

Does that one 1T4 giving me infinite OHMS mean I need a replacement?

Thanks for your website suggestions.

[codefox1]

Yes. you need a new 1T4 tube. I don't seem to have a spare or I would give it to you. Put a note on the wanted section, I'm sure someone will have one for you.

[Deathstryker]

I got all my stuff in and started soldering components. However, I came across a resistor that is different from the schematic. In the schematic, R10 calls for a 3.3M Ohm capacitor but the one that is in it is 3M instead. I ordered all of my components from the schematic so I have a 3.3M Ohm resistor. What's up with this and would I have to order a different resistor?

Did they just not have the part on hand and used what they had?

[Marsupial]

likely the .3M isn't critic at this place, or they ran out of 3.3M during 1945, or the radio was repaired somewhen and this changed. If the schematics call for a 3.3M and your radio have a 3M you should be good putting either value, or anything in between.


Did you read it on the resistor, or measured it?

[codefox1]

Those high value resistors drift a lot, so no matter which one they put in, it's a candidate for replacement. 3.3 meg is a modern value and a very good one can be had for perhaps a nickel, when you buy an assortment or stock up your stash. When I recap a radio, I routinely replace any resistor I have to disturb anyway, and most of the time nearly all of them.

You'll want to go slow and careful when you bring this one up. The most critical thing is to make sure the filament string voltage is well within specs, maybe a tad lower. If you need to add a resistor on the last leg of the supply, don't hesitate. Under load, you want to be spot on or under, never over. You will not be able to measure the string without a load with any reliability because you will be dealing with so many variables at the same time, your only option is to go slowly with a variac and measure.

Check back if you get stations on and off with thunder in the background. It'll be the silver mica capacitors in the IF cans. Four out of 5 '42 AND '46 needed help that I am aware of. But there were an awful lot of sets made, so let's not go there unless we have to.

[Deathstryker]

Did you read it on the resistor, or measured it?

I read it. I'll put in the 3.3 . Thanks guys.

On that note, one of the resistors called for in the schematic was a 900 Ohm resistor and that was unavailable so I got a 910 Ohm instead. It's over by ten. Do you think it will still work?

[Marsupial]

I am not certain what was the specs back then, but nowaday they are 5% AFAIK

910 instead of 900 is a bit more than 1% off, still well within tolerance. Just for fun, measure your 910 to see if it is truly a 910, or perhaps maybe a but lower.

rules of thumb, you'll want a bit higher rather than a bit lower, when replacing with a non-exact value.

Again, I don't know how it was back then, but nowaday, when the resistor value is critical, they have a trimpot that is adjusted at the assembly line, and shut glued in place to keep value there.

Those of us fooling with a defect radio or TV being young, adjusting those adjustment screws what had some colored goo on it, was doing a very bad thing. lol.

IMHO, the 910 instead of 900 should do just great.