[Masonparker]

Working on a H-104A did the usual recap and checked all the resistors.  The radio has good reception but the volume is low.   I checked and rechecked all the new connections all look good in that nothing is touching it shouldn't.  I checked the voltages ( see attached) The plate voltage on 6SK7 is high.  Also the voltage on the 6AT6 which was changed per the attached supplement has two pins that have high voltage.

[Mondial]

The voltages of the 6AT6 tube don't make sense. If the plate voltage is 250 V, there that means either the tube is not conducting current which it should given the other pin voltages, or the plate resistor is the wrong value.

Did you replace the resistor connected to the plate pin 7 and if so is it the correct value? Should be 470 K? What is the voltage measured across the plate resistor?

Check the circuitry around the 6AT6 and the tube itself which also could be bad.

[Masonparker]

I added the schematic that has the updated circuity for the 6AT6

The 470K (#43)  resistor is good and the 680K (#45) resistor is good

I checked the resistance of 6AT6 per the last attached supplement  ( used two different tubes)
The resistance at Pin 7 was way off. ( see page 2 of the attachement)

The voltage across the 470K is 4.1 volts  the 680K is 3.8

[Mondial]

Something definitely wrong with the circuit connected to pin 7. Are you measuring 18K to ground with the 6AT6 out of the socket? 

There should be only four things connected to pin 7: the 470K, the 680K, the C27 .05 uF, and the 150 pF C6. Disconnect each of these in turn and see which is causing the 18K reading to ground. 

Wired as per the schematic with good components there is no way to get an 18K resistance reading to ground unless there is a short somewhere.

[Masonparker]

1. measured 17.96K to pin 7 with tube out.

2. Confirmed the only four items attached to pin 7 are the 470K, 680K, C27 and C6.

3. I started disconnecting everything from pin 7 back. When I got to the 15K resistor (item 53) and removed the connection the resistance at pin 7 continually increases.

So when I disconnect the 15K (#53) and the 5mfd (8C - using 8 mfd) and the lead the goes from the 4700K (#52) to items 33 and 34
i have no resistance at pin 7 .

When i reconnect 8C and the line to 33 and 34 the resistance continually increase. as soon as i reconnect #53 and get the 18K resistance.

One question I have is I was looking at the 18K is a resistance that was to low compared the the spec at 700K

All of the above was done with the speaker socket unplugged.

Thanks for the help. Time to watch the NY Rangers play

[Mondial]

So how is there a connection between pin7 and resistor 53 and cap 8C? 

These points should be totally isolated from each other except through the common B+ connection through the 470K resistor 43. 

You need to find how there is a connection between resistor 53 and pin 7 because there should not be one. 

Does it make any difference to the resistance at pin 7 if you remove the 6Y6G output tubes?

[Masonparker]

The connection between Pin 7 and #53 /8C is through the 4700K resistor . See attached picture .

Removing the 6Y6G has no effect on the resistance at Pin 7.

Also I have looking at the connection for the center tap on the tone controller which connects to the terminal board that connects to nothing.  The schematic shows this wire connecting to ground.  I checked my before pics and this is where is was connected before i started

[Mondial]

The problem is that you have installed the wrong value resistors at 43 and 45. Where there should be a 470K resistor, you have installed 470 ohms, and for the 680K you have instead 680 ohms. This explains why the voltage is wrong on pin 7 and why the audio is very low.

Please learn the resistor color code. A 470K resistor should be yellow-violet-yellow-silver and 680K is blue-gray-yellow-silver.

Replacing these resistors with the proper ones should cure the low audio problem.

[Masonparker]

Thanks for all the help and seeing me through to the end. Once I put in the right resistors it worked great. I will not be making that rookie mistake again.

Thanks again for all your help.

Next one is a RCA 6T5

[David]

Old post from April of 2021 might be of help in the future glad you got it fixed. David   https://philcoradio.com/phorum/showthrea...#pid177816