Posts: 10
Threads: 2
Joined: Nov 2013
City: Baltimore, Maryland
Hello to all ! Just completed recapping a Philco 37-611./ This is a transformerless receiver. I replaced the paper caps, the electrolytic caps, and both bakelite assemblies. I had to replace the on/off switch (and I'm guessing this is also some sort of tone control as well).
After powering up, (no smoke, no flames)
All of the tubes were glowing but no sound from the speaker. Just the slightest hint of a hum.
I took a measurement of all the tube voltages, hoping maybe one of the more experienced members could shed some light as to the cause of the problem using the tube voltage information.
They are as follows:
25Z6G
PIN 2 = -129.3
PIN 4 = +105.7
PIN 7 = -385.2
PIN 8 = +105.7
25A6G
PIN 2 = -385.3
PIN 3 = +1.23
PIN 4 = +1.23
PIN 7 = -310.5
PIN 8 = +7.04
6A8G
PIN 2 = -310.5
PIN 3 = +106.5
PIN 4 = +14.65
PIN 6 = +1.21
PIN 7 = -233.6
PIN 8 = +1.20
6K7G
PIN 2 = -112.2
PIN 3 = +106.9
PIN 4 = +14.87
PIN 7 = -232.2
PIN 8 = +14.02
6Q7G
PIN 2 = -0.1
PIN 3 = +103.8
PIN 4 = +10.7
PIN 5 = +13.34
PIN 7 = -111.2
Posts: 7,305
Threads: 270
Joined: Dec 2009
City: Roslyn Pa
So take your - lead from your meter and connect it to the off/on switch. set meter for DC volts. Measure the voltage on the pins of the 25A6 with the + lead . Report back.
Terry
Posts: 1,106
Threads: 88
Joined: Jun 2011
City: Tacoma
State, Province, Country: Washington
These voltages confuse me. This is obviously an early AA5 design and shouldn't have any voltages over about 125.
Posts: 10
Threads: 2
Joined: Nov 2013
City: Baltimore, Maryland
ok here are the new readings I got from neg lead on/off to 25A6 pins:
PIN 2 = +291.4 mV
PIN 3 = +3.14 v
PIN 4 = +3.14 V
PIN 7 = +1.35 V
PIN 8 = +8.84 V
Posts: 7,305
Threads: 270
Joined: Dec 2009
City: Roslyn Pa
Ok so far you have no HV. Measure the voltages on the pins of the 25Z6.
Terry
(This post was last modified: 11-30-2013, 11:58 PM by
Radioroslyn.)
Posts: 10
Threads: 2
Joined: Nov 2013
City: Baltimore, Maryland
25Z6
PIN 2 = +42mv
PIN 4 = +108.6v
PIN 7 = +292mV
PIN 8 = +108.6V
Posts: 7,305
Threads: 270
Joined: Dec 2009
City: Roslyn Pa
Good, You have HV coming out of the rectifier tube. So the next thing is the field coil #48 and choke #51. Check for resistance on both parts. Bet 51 is open.
Terry
ps Welcome to the Phorum! Hope you enjoy your stay!
(This post was last modified: 12-01-2013, 07:02 PM by
Radioroslyn.)
Posts: 10
Threads: 2
Joined: Nov 2013
City: Baltimore, Maryland
the reading on part # 51 choke is 374 ohms. Not sure where to take the reading for the field coil. Is it part of the audio transformer assembly?
Perhaps you could point it out in this photo?
Posts: 1,114
Threads: 14
Joined: Feb 2013
City: Irvington, NY
The field coil is connected to the black and yellow wires going to the terminals on the transformer. You can see the wires enter the coil itself which is located at the center of the back of the speaker.
Posts: 10
Threads: 2
Joined: Nov 2013
City: Baltimore, Maryland
Thanks for the info, Mondial, the field coil reads at 2750 ohms.
Posts: 7,305
Threads: 270
Joined: Dec 2009
City: Roslyn Pa
So with the - connected to the off/on sw what DC voltage do you see at pins 3 and 4 of the 25A6??
Terry
Posts: 10
Threads: 2
Joined: Nov 2013
City: Baltimore, Maryland
Pin 3 = 1.7 vdc
Pin 4 = 1.7 vdc
Posts: 811
Threads: 43
Joined: Dec 2008
City: Chicago, IL
Where are you connecting the negative lead of your meter when checking voltages ? The chassis on this set is not ground - it's floating.
Posts: 10
Threads: 2
Joined: Nov 2013
City: Baltimore, Maryland
I have been connecting it to the on/off switch
Posts: 811
Threads: 43
Joined: Dec 2008
City: Chicago, IL
Oh, OK. I' still puzzled by your first post with voltages as high as -385 ?
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
