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Model 37-84 Cathedral - Printable Version

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Model 37-84 Cathedral - Tucker - 06-13-2021

I've recapped this radio and tested the resistors and tubes. When I bought it the filter caps were replaced with new caps but one of the terminals on the filter can was still hooked up. I corrected that and rebuilt the 4 bakelite blocks and now there's no sound.  The radio did play earlier and rather well considering the only caps replaced were the two filters. I took pictures and checked the pictures as I went and nothing stands out.
I went back over looked for a mistake but I don't see anything wrong.  I also went over every solder joint that I made to be sure it wasn't a bad connection. I took the voltage of pins on the output tube and measured;

Pin 2 = 6.26VDC
Pin 7= 17.5VDC
Pin 3 = only 1.15VDC
Pin 4 only 1.41VDC

Voltages on the rectifier (5Y4G);
Pin 7 = 374VDC

is there something obvious that I'm overlooking ?

RE: Model 37-84 Cathedral - 45philcodon - 06-13-2021

Curious,

You stated measuring the following voltages:
6F6 output
Pin 2 = 6.26VDC
Pin 7= 17.5VDC
Pin 3 = only 1.15VDC
Pin 4 only 1.41VDC

Relative to ground ---

6F6

Pin 2 should be ~6 volts AC not DC
Pin 7 should be 0 volts (ground)
Pin 3 should be greater than 200 volts DC
Pin 4 should be something greater than Pin 3


Voltages on the rectifier (5Y4G);
Pin 7 = 374VDC

For the 5Y4

There is no connection to Pin 7
Pin 8 should be something greater than Pin 4 of the 6F6

Check your ground connections, something is mis-wired to have voltages so far off.

RE: Model 37-84 Cathedral - BrendaAnnD - 06-13-2021

Wire off the speaker? Forgot to plug the speaker in? Either of those will disrupt the DC path from the rectifier.

RE: Model 37-84 Cathedral - BrendaAnnD - 06-13-2021

Also note: voltages should not be taken relative to ground, but relative to the B- bus line. The chassis will be more negative than the B- bus by around 20 volts or so.

RE: Model 37-84 Cathedral - Tucker - 06-13-2021

The speaker is plugged in. I was taking the voltages with the neg lead of my DMM attached to the chassis. I’ll try again with the lead on B- after I check the wiring against the schematic.

RE: Model 37-84 Cathedral - Radioroslyn - 06-13-2021

I'm betting on the wire from the 5Y4 filament to the field coil is open or the field coil is open. I would be surprised if a 37-84 has a spkr plug from the factory. Philco waste 20c on a plug & socket when they can hard wire it in?

<For the 5Y4
There is no connection to Pin 7<

Pins 7 and 8 are the filament connection for the 5Y4. Either pin would be @ HV+ when there is ac voltage applied to the plates and the ct is used for the negative return.

RE: Model 37-84 Cathedral - Tucker - 06-20-2021

I looked at just the rectifier tube and the wiring appears ok. The speaker is hard wired and it looks ok also. I checked the voltages from the top side this time with the 5y4g tube removed on pins 3 and 5 and Im getting 330 vac on each of those two pins with the negative lead attached to the negative side of the filter caps. 
Still no sound though and the rectifier tube isn’t lighting up. I tested the tube and it’s ok. I also replaced the 5y4g tube with another 5y4g and still nothing. I noticed if I touch the grid cap on one of the 6j7g first audio tube I get a buzz through the speaker. When I touch the center volume control tab with a screwdriver I get nothing at all. 
I’ll check the rest of the wiring later this week against the schematic.

RE: Model 37-84 Cathedral - Radioroslyn - 06-20-2021

Would check to see if you have 5v or so across pins 7&8 of the 5Y4 socket. Also check the resistance across pins 7&8 of the 5Y4's. Maybe you have two duds.