[proftrussell]

Phorum Phriends,

I have some questions about resistors in my 42-345. 

Before getting to the confessional aspect of my post, I'd like to say first that I have fixed up my 42-365, which I call big Phil. I replaced the electrolytic capacitors and another paper capacitor that looked like it had a pustule. I installed a new power cord and replaced some of the rubber wiring. I fixed the dial cord. I also added green LED lights to replace the original dial lights. The radio sounds great and looks great, too. I love it.

Alas, I got a little cocky with my 42-345, which I call Little Phil. I deviated from my rule of doing just one thing at a time to see whether the radio worked afterwards. This sloppiness led me to rush, and I replaced an electrolytic capacitor with the polarity reversed. In the attached schematic, the capacitor is number 57, which connects between 7Y4 and 7B5. 

I may have made other errors; I cannot tell yet.

What happens if you put the capacitor in the wrong way? At first, nothing. The radio played and played beautifully for about five minutes. My employee and I enjoyed it. He left for the day. I listened a bit longer, and then the sound stopped. I went over to look at the radio, and 7Y4 was glowing brightly red. I smelled a little something. I unplugged the radio. I look later the capacitor, which did not blow up, but looked a little scorched at one end.

My questions for the Phorum are easy. My questions are about the value of the various resistors. 

In the first photo, there is a big resistor in the back with two red rings, one brown, and then silver, I think. This is 33-122436, a 220 Ohm resistor. Correct?

Beneath the double red band is a blue, grey, black, silver resistor. This is 33-068136, 68 Ohms. Correct?

Are they both ½ watt? 436 and 136 mean something, but I forget what.

Next, brown, black, green. Am I right this is 33-510339 and 1 Megaohm? 

Last, there's a red, red, followed by, I think, yellow? if so, that's 220,000 ohms and 33-422339. Right?

My brother, who actually knows something about electronics, assures me that the resistors were not the cause of the smoke that I saw when I plugged Little Phil in. Take a look at the 220 Ohm sausage, and you'll see a crack where the smoke came out. Same with the 68 ohm, which appears scorched.

First, I'd like to know if I have the parts right, because I will replace them.

Second, I guess I would like to know if the damage is consistent with the mistake that I think I made. (Another hypothesis would be that I did something wrong with the other capacitors I replaced or maybe I created some kind of short.)

Feel free to guide me regarding my plan. Keep in mind that while I can solder and am not stupid, I'm not very knowledgeable about electronics. I also only have a multimeter, nothing fancier.

My plan is to 
1. confirm the polarity of the 12 uf capacitor and put it in the right was the next time. 
2. I am also confirming that I soldered everything to the right pins. I have a vague worry that I'm on the wrong pin.
3. I am going to replace the burned up 220 and 68 ohm resistors along with, I think, the others about which I asked. 
4. I am going to put a new 7Y4 tube in. I may not have wrecked that one, but I don't know how to test it, so I bought a new one.
5. I'm also rechecking the wires to see that I did not melt anything.

After doing this, I hope to have Little Phil back in action. What say ye?

Thank you,

Tom Russell
Denver, CO

[morzh]

You seem to have gotten the values right.
Yes the damage is consistent with a wrong polarity of the first rectifier filter.

Now you have to change the cap, probably the tube also.
If possible, check the rest.

Remember: the Cathode (K) of rectifier leads to Positive opf the cap, and vice versa.

Now.
You have a few other caps, including some tubular paper caps and the big tubular electrolytic.
They all have to go.
Do not leave them in. If you don't restuff the caps for looks, just get some yellow axial capacitors and use them according to their values.
The #61 caps 0.1uF have to be Y-rated safety type.
If exist, Mica capacitor (rectangular brown, usually) should not be touched, and preferably not soldered/touched up.

As for the resistors, for the 220 ohms use at least 2W-rated one. For 68 Ohm use at least 0.5W.
For 220K and 1M the power rating is not critical, 1/4W is plenty, but for convenient soldering I prefer at least 1/2W, and usually use 1W.

I also took the liberty of correcting your thread name from " 32-345 Resistors" to 42-345, as it seems to be your radio.

Mike

[proftrussell]

Mike,

Thank you for the reply and for correcting the year on my subject. Little and Big Phil are indeed 42s.

The big, dumb mistake that I made was replacing an original black wire with a red one and a red one with a black one; I then relied on the colors to connect the capacitor the next day. Several lessons learned.

I did not want to replace all the paper caps only the ugly ones, but I will do so as maybe a bit of penance or in order to make it up to Little Phil.

Glad I got the values right. Thanks for the tips about power ratings. That's all mysterious to me. I do not know what "Y-rated" means, But I'm educable.

I'll check in when I get the repair work done.

Thanks again,

Tom Russell

[radiorich]

Hello Tom,
I hate that when that happens We have all been there and here is a short video and page  about safety capacitors .
Sincerely Richard

safety capacictors

video

[DaleHCook]

Those wax-paper caps, if they have not already failed, are very likely to fail, and the same is true of the old electrolytics. That is why experienced restorers generally replace all of them before they even try powering up the radio.

[Paul Philco322]

To not replace is to put it on the list to do later when they cook up! As a radio guy would say back in the day, lets spend the time and will have no "callbacks".

Paul

[morzh]

In short (I a sure you've seen the video Rich provided), safety caps are X and Y.
X caps are placed across the Line/Neutral to filter differential noise.

Y caps are placed between the isolated parts of device, one being at a dangerous voltage referenced to Earth (either AC line or any voltage directly derived from it while being galvanically coupled to it, like rectifier, boost converter and such) and the other being the user touchable end, usually chassis GND.
This caps are to filter common mode noise.
Because they go to User end, they are made so that they are guaranteed to always fail open, thus avoiding electrocuting the poor user. They are typically not very high in capacitance.

[proftrussell]

I replaced all the electrolytic capacitors. That big Philco 12uf 400V electrolytic Vienna sausage. is one I removed and then put back in, briefly, after I fried a replacement by reversing the polarity.

I had thought I would just replace the electrolytics and the obviously bad paper caps. But, all y'all are like crack dealers each giving me a little instruction and push, so I ordered all new caps and resistors yesterday from Mouser. Plus a couple of new tubes from another source.

I'll report back whether I revive or kill little Phil. It's going to take me a while.