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?
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
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
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.
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.
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".
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.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
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.
I'd like to say that I took heart from a comment by Morzh (Mike), who, after I made some errors with my 42-345, said, basically, we've all been there. Elsewhere, too, I think he commented that putting stuff back together after we mess it up with an error is very satisfying. I agree.
I have Little Phil, my 42-345, back in action. I cannot say precisely what put Little Phil back on track, but I replaced two tubes of which I was suspicious after the wrong-way electrolytic capacitor fiasco, confirmed I had wired things right with some other replacements, and replaced a few sketchy wires. Little Phil is back to working!
I can now get back to replacing the paper capacitors. I had replaced the electrolytics already. I will do one at a time now, which was my original rule.
Two other things:
1. Speaker issue. I am not sure of the word, but I have a speaker vibration issue—not a hum or buzz—but a rattle, maybe? There may be a little defect or tear in the speaker, and I am going to get some speaker or fabric glue to apply to the back (I think) of the speaker.
2. FrankenPhil. To help recover Little Phil, I bought a 42-345 for not much money at all from a Facebook seller in Albuquerque. The interior of the case was dusty and mice had visited to eat sunflower seeds, so I figure there is radioactive fallout and hantavirus inside.
My original idea was that I would transplant parts from FrankenPhil into Little Phil, but now that Little Phil is working, I think I will try to get FrankenPhil working, too. The machine powers up. The speaker is shot—not holey but the cone is completely gone. I'd like a temporary workaround. First, can I connect a multimeter to FrankenPhil to see if there is output? If so, which of the three wires and on what multimeter setting.
I also wonder if I can connect the old coil speaker to a $2 permanent magnet speaker just to see if FrankenPhil wants to sing. I'll post photos in another thread to make clear what I mean.
The big news, though, LittlePhil, my 42-345 is no longer emitting smoke and is back to working pretty darn well! Satisfying, as Mike said.
1. I was about to say what you later said you'd like to do. Change the speaker, see if a know good one rattles also. Use the same or large size.
2. Yes you could connect a "coil" speaker, if you mean a speaker with the field coil. However you will need to energize the coil, which require some decent voltage of a few 10s of V. Depending on where the old speaker came from, try to find a suitable power source, fairly clean, and then see if it works well.
But nowadays large PM speakers are not rare and fairly inexpensive. I would just buy one. I have a couple for this purpose only: got both for $1 in Kutztown.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
What I was thinking was that I have the OEM speaker from Little Phil, but the mice and radioactive fallout completely eliminated the cone.
Can I put that speaker back in place, connect the three wires, and then hook up my spare little Jensen permanent magnet speaker to the original field coil speaker? This would not be a permanent solution, just something to see if music comes out.
What is the coil resistance of your OEM speaker?
YOu should then disconnect the Voice coil of it and connect your PM speaker to the output xfmr secondary instead.
Or, connect only field coil (2 wires) and then use a different output xfmr to match your PM speaker to 7B5 tube.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
There's several ways to check the speaker. In these older sets the field coil will usually leave residual magnetism in the pole. If you intermittently connect a battery between the plate and screen grid of the 7B5 you should hear clicks in the speaker. That, of course, is when the cone is present. Maybe you'll hear clicks, maybe not. You should feel the voice coil moving. If this is successful, the opt and speaker are capable of producing sound. If not, then one or the other is probably defective. Use an ohmmeter at the same tube pins to test the opt primary.
Yes, for testing purposes, you could hook the remnants of the OEM speaker to the radio and hook a PM speaker to the secondary of the output transformer. For testing purposes, a mismatch between transformer impedance and speaker voice coil impedance is not horribly important. For the permanent repair, however, if replacing the OEM speaker with a PM speaker, the impedances should match. The 7B5, 6K6 and 41 are essentially the same tube. B+ for the output stage on this set is 180V. The 1940 RCA Receiving Tube Manual states to use the 6K6 specs for the 7B5. However, the specs for the 6K6 in this manual does not list Plate Load Resistance at 180V. for 250V, the Load Resistance is 7600 Ohm. However, the 1937 RCA Receiving Tube Manual lists a Plate Load Resistance of 9000 Ohms for the 41 at 180V.
The field coil can be substituted with a 1700 Ohm resistor with a minimum of 10 Watt capacity. It is recommended to increase the capacity of the filter caps to maybe 20 uF for the first cap and 3o - 47 uF for the second cap. Monitor the B+ to ensure that it does not increase too greatly. A choke with a resistance of 1700 Ohm can be used but I don't know what the inductance would be.
Funny comment about the radioactive dust and hantavirus, but do be careful. At the least, sensitization to hantavirus can cause erroneous test results on a lot of tests for therapeutic drugs like digoxin, some antibiotics, etc., which use immunochemical techniques involving mouse derived antibodies. At worst, hantavirus respiratory syndrome can kill you. Definitely wipe the cabinet and chassis down. Keeping things wet with 70% isopropyl alcohol is effective. So is 10% dilution of fresh household bleach, but hey, you do want this thing to work.
We all make mistakes, some little, some spectacular. You did learn an important lesson. Electronic, electrical and mechanical systems work on smoke. How do I know this? Because when you let the smoke out, the device stops working. I was once working on an old HP computer terminal (from the days of mainframe computers) with an analog voltage regulator for the 5V supply. There was no output. I found a Zener diode that was across the output to be shorted so I cut it out of the circuit. I then powered it up, after a few seconds, I heard some funny ticking noises. I noticed the smoke just before the filter caps blew off the PC Board leaving a stream of paper, aluminum and electrolyte. The can hit the wall 12 feet away. Every chip cracked open like your resistors. It didn't dawn on me that the Zener shorted because the pass element shorted and put about 35V across the caps and chips after i cut out the Zener. With both parts shorted, the transformer and a dropping resistor of high wattage were handling the voltage drop.
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
