I have restored this poor Philco to the point where I can actually test it but when voltage is applied all I get is a very rythmic thumping sound from the speaker. It remains constant and is unaffected by tuning, volume, or band selection. I checked all my wiring and component installation and everything looks correct. What have I done wrong?

Ok I goofed. I had the 6K7 and 6Q7 tubes switched. Now the thumping is gone and has been replaced by silence. Just a very low level buzz that is unaffected by volume control. Same buzz across all three bands. I triple checked my repairs and they all look correct. All the tubes test strong. I'm stumped...

Hey that's not bad, assuming nothing is overheating. A good starting point for troubleshooting!
Just take it step by step, isolate to the defective stage then component.
From here, if it were me I'd unplug the soldering iron and touch the tip to the wiper connection on the volume control.
A buzz means the audio section is probably okay, if so work back toward the antenna from there.

Best wishes,
-Sam T.

You might also let us know what you have done beyond replacing capacitors. Also whether or not any switch cleaning has been done (lot of switch contacts in that radio).

Voltage checks at the tubes are a pretty good thing to do. Also putting another radio nearby tuned to something like 1070 KHz while you tune the 610 back and forth around 600 KHz to see if you can hear any Local Oscillator signal coming from the 610.

Curtis Eickerman

I cleaned everything on this set. Switches. Pots. Band switch. Tuning cap. Tuning gears. All of it. I tried to do everything right because the guy before me sure did'nt. Would it matter that the 6Q7 tube is metal? I believe the pins are slightly different between the original "G" style tube and the metal tube. And I know Philco did not care to use metal tubes in their sets. I would swap it but I dont have a 6Q7G. The wiring for the 6Q7 socket is original. No wires changed around.

The only pin difference is that the metal tube has pin 1 connected to the metal shell as a built in shield. So if the radio originally had a shield on the 6Q7G and you use a 6Q7 without the separate shield, you probably should make sure pin 1 on the socket is connected to the chassis. Otherwise the tubes should behave the same unless the circuit is real finicky for some unknown reason.

Curtis Eickerman

Pin 1 is connected to pin 8 and then to the chassis. Pin 1 also has a .1mfd cap connected to it which goes to a terminal strip where its connected to a 1meg resistor then to a wire that goes to the grid cap of the 6Q7.

All of the connections you mention sound fine. The cap is just using that as a convenient ground connection. 8 is the cathode which is also grounded. The 1 Meg does indeed go to the grid connection.

I see no issue with using the metal tube.

Curtis Eickerman

Ok. Did voltage check and I'm about 80v low pretty much across the board. The rectifier tube tests strong and the transformer is fine. I'm pretty sure this is my problem and I'm definitely sure I don't know whats causing it.

Is your power resistor (54 on the Riders) OK? You might have an open resistor in it..

What value of filter capacitors did you use?

#54 is the multi-section resistor? Mine is testing way outta spec. The first section (202ohm) is reading 145ohm. The next two sections are both reading over 100ohm. I used two 22mfd and one 10mfd lytic. As luck would have it I don't have any of the necessary resistors in stock.

If the voltages are within 30% then thats probably not the signal killer. I,would start touching a screwdriver to the volume control center pin, with the volume control halfway up. Ou should get a buzz hum or click. If not, there is a problem after that point, if you do get a hum, buzz or click, the problem is before there. That helps eliminate half of the radio from the problem area.

I can inject signal at the cap of the 6A8 and hear it through the speaker but its very faint even with the volume all the way up. Touching the volume pot center tab gets me a clicking/buzzing sound but barely audible.

Start with what you already know is wrong. I think you need to measure that power resistor out of circuit (disconnect some wires). It should read 202, 8 and 35 ohms; maybe your last two sections are open.

After that, you might need a new 6A8G (even if that one test OK); they can be a problem.

I highly recommend cleaning that band switch assembly. Make sure your oscillator coils have continuity.

The band switch is nice and clean. I have some extra 6A8 tubes to test with. I will remove the resistor and test it out of circuit. Has to wait til after work though. I owe.. I owe.. its off to work I go......

Until you get the audio section working strongly, it will be difficult to move towards the front end. I would start with some voltage readings on the output tubes and the 1st RF section. Biasing being off on the output tubes could cause excessive current being drawn and lower voltages overall.
Jerry

I tend to agree. You might do something like this where you record any voltages that you know are required based upon the schematic or other documentation. Then record the voltages you have actually measured.

This makes it easier to see the discrepancies.Curtis Eickerman

I understand this radio is still not working. I also understand that all the voltages seem to be low (there can be a variety of reasons).

So, here is what I suggest. Remove the tubes except for the 5Y4. Then measure the voltages indicated on the previous chart for this tube. Please measure these relative to ground. Also measure the voltage at the positive connection of capacitor 53 (8 uF). Tell us what voltages you are actually seeing. The actual values are important.

Once this is done I would suggest you install the 6F6 and redo the above measurements plus those listed for the 6F6 on the previous chart. Again tell us what voltages you are actually seeing.

As we work through this the goal is to determine what is causing the low voltage readings AND get the audio section running so that it can be used to work through the rest of the radio.

Curtis Eickerman

Gotcha.. I'm on it..

Before doing the above mentioned voltage checks, and just to sate my curiosity, I injected signal directly to the volume pot's center tab and the signal played loud and clear through the speaker. I could not adjust the volume with the pot though. Only adjusting the signal's volume worked. Voltage checks are forthcoming.