[Patrick]

I have a U.S. Radio Gloritone 3072, also known as an Apex 70. The schematic leaves a lot to be desired. Some of the resistor values aren't indicated, can't read some cap values, and weird things like a 500K resistor parallel to 2 sections of the candholm. There has been a lot of previous work done, and I want to put it back to it's original state. Can't find another schematic anywhere, nor any reference to the model.

Can anyone assist filing in the blanks?

Thanks,

Pat

[Image: https://i.imgur.com/7sjP1gZ.jpg]

[Radioroslyn]

So what values are you concerned about?

[Patrick]

Only the obvious ones. Resistor off of grid of 47, resistor on the bottom of the volume control, value of cap between the 2 8 mike 'lytics, why is there a 500K resistor in parallel with the 130Ω and 400Ω sections of the candolm, value of the cap to ground near the cathode of the 56, and any other obvious ones I missed.

[Radioroslyn]

>Resistor off of grid of 47, resistor on the bottom of the volume control,
Your looking @ abt 250K to 500K 1/2w it's supplying the bias for the 47 tube. Value not very critical.

>value of cap between the 2 8 mike 'lytics,
1mfd 630v mylar  it's there to tune the field coil to 60cy.

>why is there a 500K resistor in parallel with the 130Ω and 400Ω sections of the candolm
Not sure but because of the other resistors it's pretty much invisible because of it's high value.

>value of the cap to ground near the cathode of the 56
Small value as it's bypassing rf out of the audio signal 100-200mmfd.

GL

[Patrick]

That helps. Thank you.

[Patrick]

Well...something in this circuit is not right. Voltages on either side of the field coil seem to be alright, around 280VDC, but plate voltages (except for the 47) are 0. The actual wiring on the candholm made no sense. It has 4 lugs in a row. The first lug is as shown in the schematic. The second lug measured 300Ω from the 1st. The third lug is ground. Resistance between 2nd and 3rd is 90Ω. Between the 3rd ground lug and the 4th is 4KΩ. And there was a 4KΩ 2W resistor between the 1st lug and the last.So I replaced the 130Ω section with 150Ω 10W, left the 90Ω section, and replaced the 100Ω section with 85Ω 10W (that's all I had on hand).

I traced all the wiring several times. Every thing appears correct, according to the schematic. I still think there might be an error in the original schematic, but my lack of knowledge is preventing me from analyzing it.

[Radioroslyn]

So do you have plate and screen grid voltage on the 58's?
If so check the resistance between pins 2 and 4 on the 47 tube should see a few hundred ohms.

[Patrick]

Whoa. Screen grids on 58s = 42VDC. Plates are -4VDC. Resistance between 2 and 4 on 47= 1500Ω.

[462ron]

It looks to me like there should be a connection between the second 8 mfd. cap and that 50M resistor. That would explain the reason for no B+ on the plates of the 58s. The dot appears to be missing on the schematic!

Ron

[Radioroslyn]

Did you have the spkr plugged in?? If so would seem that your field coil is open. Check it's resistance (4K).The output transformer awful high in resistance too (read bad).

[Patrick]

Field coil is right at 4K, and I get around 285VDC on both sides. I do get a clicking from the speaker when I input a signal on various plates. What do you think about Ron's idea?

[Radioroslyn]

Yes there is a dot missing @ the intersection of the top of the 2nd 8mfd cap and the 1mfd non polarize cap that is in parallel with the fc. That should get you HV up in the rf and IF sections. Are you getting any high voltage on the plate on the 47?

[Patrick]

Thanks Ron. That's it! Don't know how long it would have taken me to figure that out. And thanks to Terry, too.

Just need to align it now, but it picks up stations all across the dial.

Pat

[462ron]

YW Pat, glad it's singing for you!

Ron