Philco 37-611 Restoration (Newbie Here)
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: 7,286
Threads: 268
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: 1,108
Threads: 89
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: 7,286
Threads: 268
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: 7,286
Threads: 268
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: 7,286
Threads: 268
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: 797
Threads: 42
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: 797
Threads: 42
Joined: Dec 2008
City: Chicago, IL
Oh, OK. I' still puzzled by your first post with voltages as high as -385 ?
Users browsing this thread: 3 Guest(s)
|
|
Recent Posts
|
|
HiFi (Chifi) tube amp build - but my own design.
|
| Mike, Tim; you are about to enter the twilight zone. Doo doo doo doo, doo doo doo doo
This is something alright. I'm go...RodB — 06:26 PM |
|
HiFi (Chifi) tube amp build - but my own design.
|
| :lol: We need to start a singing radio group! I play the guitar, so maybe get a few vocals? Anyways, Mike, I did try mou...TV MAN — 05:56 PM |
|
HiFi (Chifi) tube amp build - but my own design.
|
| And so does a barber shop quartet. mmmmmmRodB — 03:54 PM |
|
Shadow Meter Bulb
|
| I did try an LED bulb in place of the original but wasn't impressed with the amount of light on the dial. Seems like it ...RodB — 03:51 PM |
|
HiFi (Chifi) tube amp build - but my own design.
|
| Tim
Would mounting he transformer vertically change the hum, if used without additional parts?
Also, in these amps...morzh — 02:25 PM |
|
Shadow Meter Bulb
|
| Gary
I doubt it would introduce any noise. We use similar lamps for the panel indication, 12V AC lamps: they are LEDs...morzh — 02:15 PM |
|
Shadow Meter Bulb
|
| Not sure if anyone has tried this but there are 6.3 volt miniature lamps in bayonet and screw-in base options available ...GarySP — 11:31 AM |
|
Shadow Meter Bulb
|
| Any 6.3 volt pilot light will work. I would use the brightest one I could find in my workroom. Be sure the dial is clean...RodB — 10:45 AM |
|
HiFi (Chifi) tube amp build - but my own design.
|
| Tim,
nice write up and thanks for sharing !!
Sincerely Richardradiorich — 02:47 AM |
|
HiFi (Chifi) tube amp build - but my own design.
|
| Well, this was a real "Hum-Dinger" :lol: ! This will be kinda long, but hopefully it will help others having t...TV MAN — 01:55 AM |
|
Who's Online
|
There are currently 6968 online users. [Complete List]
» 1 Member(s) | 6967 Guest(s)
|
|
|
|
 
|
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
