I have an RCA 1X51 and have replaced caps and checked resistors. I have no sound output except very faint hum that does not change with volume. I do get sound when hooking up signal generator to loop antenna. Since I get sound, can I assume that I should be able to get a station? I am not sure what to do. Sorry, search function on here I cant find anything


http://www.nostalgiaair.org/Resources/808/M0014808.htm

1. Are you sure the tubes are all in the correct sockets? They probably are since you get some sort of audio but check anyway.
2. Touch your soldering iron to the center terminal of the volume control. Loud hum?
3. What signal are you connecting to the loop antenna: what frequency on the signal generator? Does it tune up and down the dial?
4. Put a good operating radio tuned to 1400 next to your RCA. Tune the RCA up and down between 800 and 1200. Should hear the RCA oscillator in the other radio.

More tips after you try these.

Yes to soldering iron-Load Hum
Tubes-Check
Sig Gen-I am not sure if I am even using it right,. I have no manual. Heathkit SG1. I assume RF, since that is the where I have the leads plugged in. It also has "AF" but I have no idea what that is. Anyway, on "RF" I am at 455, then to 900, then to 1100 area. Has signal these areas.
Good Radio-It did pick up the RCA tuner.

So im screwed right? LOL

You should really have this set connected to an isolation transformer to be safe. Do you?

1. Check the tube voltages. Meter set to read at least 200 volts DC. Negative meter lead on negative side of electrolytics: best to use a test lead with alligator clips to keep it there while you probe with the other lead. Voltages are shown on the schematic next to tube pin numbers. Check volts on plates and screens of 12BE6, 12BA6, 50C5. Plate of 12AV6. Cathode of 35W4. Let us know the voltages you find.

2. If volts all seem reasonably close to schematic, try injecting signal from your signal generator. Set the Signal generator for RF output, internally modulated. This puts an audible tone on the RF carrier wave that the SG produces, like a mini radio station. Set the SG to 455 kHz. Set the output of the SG about half way. Clip a small capacitor (.001 or any small one is fine) to the SG center wire output cable. Keep the shield ground of the output cable not connected to anything and tape it up out of the way to the cable. Use the other end of the small capacitor as a probe. BE CAREFUL and deliberate in what you're doing with the RCA turned on volume about halfway. Bring this "capacitor probe" to these tube terminals and let us know what you hear and the relative loudness of it in the RCA speaker compared to the other tube terminals in the test:

12AV6 pin 5
12BA6 pin 5
12BE6 pin 5

Edit: forgot to mention: the fact that the good radio picks up the RCA oscillator is a sign that the oscillator is working. Question: are both wires from the loop antenna connected firmly where they should be?

Here are the voltage I was able to get, if I did it right.

12BEG
PIN 6=79
PIN 5=76

12BA6
PIN 6=79
PIN 5=76

12AVG
PIN 7=52
DIDNT SEE ANY OTHER PINS ON SCHEMATIC TO CHECK.

50C5
PIN 7=85
PIN 6=75

35W4
PIN 7=98

That is what I see on the schematic.
As for the cathode , I am not sure what I am looking for.

Btw, I do now hear a soft hum not responding to volume. Didn't hear it before.

pins count clockwise from the right of the key , from 1 to 8 while looking at the bottom of tube socket where wires are soldered

12AV6 pin 5-Medium sounding hum, good volume
12BA6 pin 5-very low volume, high pitch sound
12BE6 pin 5-Medium sounding Hum, good volume.

THANK YOU SO MUCH FOR HELPING!

We'll get this figured out amongst us. Your voltages are 75-80% of what they should be. There's something funny about the schematic around the 35W4 also. The parts list calls for C10A and B, 30 and 50 mfd respectively, 150 volts. Today we'd use the closest modern equivalents at 160 volts, probably 33 and 47mfd. although a larger one could be used for B. The schematic shows C10B twice, down coming off the cathode (pin 7) of the 35W4 and also coming down off the screen of the 50C5 (pin 6). The one shown off the cathode of the 35W4 is incorrect and should not be there. How do you have it wired?

Also: is your pilot light present and does it work?

Have you tested the tubes or do you have others you can sub, or can you sub this radio's tubes in another good radio to test?

Good morning,
I have the 50uf 160v coming off pin 6, just where I took the original off. I have the 30uf off the 35W4 pin 7, original was wired here too. Pilot light is working. I swapped some tubes out and I now get one station with mild satic in the backgroung. Progress! I am not sure what freq I am picking up is arounf 700. Whats next? Why do plate voltages get low? I just want to understand what I am seeing. I need to know what is meant by "cathode". I have had this mentioned but have no clue where this is on that tube. One thing to mention too, suspecting a little bit of antenna issue, someone has rewired it with waht looks like electrical cord wire. Would the resistance of this wire cause issues too?Thanks

Another confusion. I have 2 sets of schematic for this radio pulled from Nostalgia. One shows the 30 coming off pin 6 on , the 35W4, the other pin 7. On the other schematic, it has differnet tubes showing a 12sq7, 50l6-gt, 12sa7, 35Z5-GT,these are the differences. the 12ba6 is the only one the same between the two. But i am running 12be6, 12BA6, 12AV6, 50C5, 35W4.

Tube elements.Curtis Eickerman

This are the older big "octol" tubes with the bakelite bases.

These are their smaller counterparts in tubes which no longer had the bakelite bases.

Curtis Eickerman

Your electrolytics are hooked up OK. Curtis pointed out the schematic differences. Sometimes manufacturers had two or more versions of a set: in this case, some runs were made with different but equivalent tubes. This was especially true right after WWII and during the Korean War when parts were in spotty supply and they had to use what they could get.

As long as the wires from the antenna are insulated and not shorting to anything they should be OK.

We really need to know if all the tubes in the set are good. You said you swapped some, but weren't specific. A tube can have a short but still work some and drag down the B+ voltage.

Check resistance of R11, 1200 ohms, and R8, 220K or 220,000 ohms. Someone else may have another suggestion about the low B voltages.

Reece,
R11 reads 1932
R8 reads 234000

I do think there is a problem in the antenna. I was moving ti around to get it out of the way and the radio stopped making sound, which is now all motor boating. When I was getting a station, the guy sounded like he was under water. Decent volume tho. Anyway, I am about to put it back on the shelf and worry about it another day.

Check for a broken wire at the antenna connection.

I came to the conclusion that the issue is that I cant read the schematic well enough and replaced a few resistors wrong I think. Anyway, i found the NRI course on the net for free, downloaded it and will study it then in a few weeks be back, THanks for all the help,

A good way to learn about schematics is to print it out and then use a highlighter marking off each wire as you trace them in the radio. Start with the power plug and work though the power supply, audio output, first audio, detector, IF, osc, back to the antenna. Check all components as you go. One wire at a time. Slow and methodical.