[Tgace459]

Greetings! First post here.

Im a newb to restoration. I recapped and refinished my great grandmothers Philco 42-321 without much issue and enjoyed the process immensely so I picked up a 37-61 to try.

The 37 was/is much more of a challenge. The chassis was in far worse shape in terms of rust and brittle wire insulation.

So...Yes, I broke the newbie cardinal rule and replaced all the caps right from the get go. In my defense, some of the caps looked pretty bad already and the wiring to the speaker and transformer (and in several other spots) were so bad that it seemed foolish to desolder and replace everything I had to replace only to dig through it all a second time to recap one or two at a time.

I took what I thought to be copious notes/photos and markings and took my time.

Anyway. I dim bulb tested it (adding one tube at a time) and it powers up safely. The tubes light up, the pilot light comes on, etc.

Problem is there is absolutely no sound from my speaker. No hiss, no hum, no static...dead silent.

I am not an expert in electronics and am just starting to get a working understanding of schematics but I've done my best to check my work against the schematic and it looks as good as I can make it out. After doing a little research about troubleshooting I tried a couple of things. I tried touching the grid cap of the audio tube...nothing. I pulled the power tube while it was on...no sound. I can cross the speaker contacts with a 9v battery and get a very faint scratching sound but when powered up the voice coil rod has only the slightest hint of a magnetic pull on my nut driver. All the wires on the transformer and coil appear to be connected.

Am I correct in assuming that the voice coil is most likely shot and not start digging too deep into anything else till I get a new speaker to try? One of the old dog-bone resistors (9000 ohm 2 watt) attached to one of the filter caps is testing way over spec. 24k ohm on a resistor specd for 9k. Any possibility that could be part of the problem?

Of course it looks like it's gonna be a @#$%^ finding the same Philco #36-1009 speaker and I don't have any other electrodynamic speakers laying around to test on so now I'm in a holding pattern.

[KCMike]

  Welcome to the Phorum. Did you check the output transformer and field coil for continuity? #37 & 38 on schematic.
There are guys on here that can give you more advice on what to check further. Here is a schem. of the model you have.
http://www.nostalgiaair.org/pagesbymodel...013208.pdf
Good luck.

[Steve Davis]

Welcome to the Phorum There is plenty of help available right here.

The first thing to try would be, touch the center terminal of the volume control. You should hear a 60 cycle hum. If you hear a hum, that tells us the 6F6 and the 6Q7 tubes are working. It also tells us the complete power supply is working. If you do not hear the hum, take voltage readings on all the pins on the 6F6 and the 6Q7 and get back to us.

Steve

[Eliot Ness]

Here is a link to the schematic for anyone else following this thread:

http://www.nostalgiaair.org/pagesbymodel...013208.pdf

I'll let one of the resident experts chime in, but until then you might want to check some tube voltages.  You can also check the output transformer ( #38 ) for 400 ohms.

I doubt that one resistor is the problem, but if one of them is out-of-spec that much then there are probably more that need to be changed.

[Radioroslyn]

Greetings! First post here.

Im a newb to restoration. I recapped and refinished my great grandmothers Philco 42-321 without much issue and enjoyed the process immensely so I picked up a 37-61 to try.

The 37 was/is much more of a challenge. The chassis was in far worse shape in terms of rust and brittle wire insulation.

So...Yes, I broke the newbie cardinal rule and replaced all the caps right from the get go. In my defense, some of the caps looked pretty bad already and the wiring to the speaker and transformer (and in several other spots) were so bad that it seemed foolish to desolder and replace everything I had to replace only to dig through it all a second time to recap one or two at a time.

I took what I thought to be copious notes/photos and markings and took my time.

Anyway. I dim bulb tested it (adding one tube at a time) and it powers up safely. The tubes light up, the pilot light comes on, etc.

Problem is there is absolutely no sound from my speaker. No hiss, no hum, no static...dead silent.

I am not an expert in electronics and am just starting to get a working understanding of schematics but I've done my best to check my work against the schematic and it looks as good as I can make it out. After doing a little research about troubleshooting I tried a couple of things.  I tried touching the grid cap of the audio tube...nothing. I pulled the power tube while it was on...no sound. I can cross the speaker contacts with a 9v battery and get a very faint scratching sound but when powered up the voice coil rod has only the slightest hint of a magnetic pull on my nut driver. All the wires on the transformer and coil appear to be connected.

Am I correct in assuming that the voice coil is most likely shot and not start digging too deep into anything else till I get a new speaker to try? One of the old dog-bone resistors (9000 ohm 2 watt) attached to one of the filter caps is testing way over spec. 24k ohm on a resistor specd for 9k. Any possibility that could be part of the problem?

Of course it looks like it's gonna be a @#$%^ finding the same Philco #36-1009 speaker and I don't have any other electrodynamic speakers laying around to test on so now I'm in a holding pattern.

Hi and welcome to the Phorum!

http://www.nostalgiaair.org/pagesbymodel...013208.pdf

>So...Yes, I broke the newbie cardinal rule and replaced all the caps right from the get go.
Not a bad thing at all as long as you got them all in the proper places.
>Anyway. I dim bulb tested it (adding one tube at a time)
A bit of a quicker way to do this is to start with all the tubes in but the rectifier try it and then add the the rectifier tube. Connect a voltmeter to the cathode or filament to monitor the HV output. On this set you should see about 250-300vdc.
>Problem is there is absolutely no sound from my speaker. No hiss, no hum, no static...dead silent.
Just fixed a set like that a little Admiral.
So let;s check some voltages to see what is going on. Goto the 6F6 tube and measure the dc voltage from the chassis- to pin3 + and do likewise with pin 4. Should see about 250vdc or better.

Terry

[Tgace459]

Thanks folks!

I'll try your advice later today when I get home.

I did try some continuity tests on the speaker, but I am still learning so I don't trust my experience to be 100% confident in my results.

I did get continuity on the output transformer, but I couldn't get it on the coil. However my multimeter is a bit finicky with it's continuity test. I can get no continuity at first but then get a positive result when I move/adjust my probes.

On the pin voltage testing. To access the pins on the 6F6G tube it looks like I may have to unbolt that wire wrap resistor from the chassis and pull it out of the way. Is that correct?

[Radioroslyn]

>On the pin voltage testing. To access the pins on the 6F6G tube it looks like I may have to unbolt that wire wrap resistor from the chassis and pull it out of the way. Is that correct?

If you do make sure that you do not lose the ground connection at the end of the resistor. Don't know if it is though a lug to the chassis though the bolt that holds the resistor or there is a wire going to a ground lug. Without that connection there will be no negative return (B-) for the power supply.

Your 9K resistor is the high voltage feed for the mixer tube (6A8 ). Best case set will work with low sensitivity worst case not enough HV to make the local oscillator run hence no reception. Won't damage anything.

Terry

[Tgace459]

OK. I snuck home and checked the pin voltages against the schematic I have:

http://imgur.com/ggZ13XJ
[Image: http://i.imgur.com/ggZ13XJ.png]


I tested all except the 6F6G from under the chassis with the tubes in. Due to having to move that darn resistor I tested the sockets from the top with the tube out for the 6F6G.

They all are off and oddly consistently off...so much so that I rechecked several times to be sure I was seeing things right.....which I assume means something to you guys with the knowledge.

PS-I did the "touch the center post of the volume control" thing. Zip on any noise.

[Radioroslyn]

> I tested the sockets from the top with the tube out for the 6F6G.
Need to test with it in the socket.
What that does tell us is that the power is working, the field coil in the spkr is good and the output transformer primary (this is the part that wound be suspect to failure) is good.
Terry

[Tgace459]

> I tested the sockets from the top with the tube out for the 6F6G.
Need to test with it in the socket.

Terry

Ill try again...it looks like the tube is insulated from the chassis...there are paper (?) washers insulating the bolt from it. I'll move it and post results.

[morzh]

Did not realize the 6F6 was out of the socket, then the voltage is good.

Dumb question: is your speaker good?

I dealt with just that recently - 4 weeks ago I tested the radio with no sound.....turned out one of the voice coil leads was not there so the output transformer was not driving anything. But if you test across the output you will see the continuity of the secondary coil.

See if you can unsolder one output lead of the transformer and measure across the voice coil.

[Tgace459]

All of the "other than 6F6G tubes" were tested with 6F6G in. I tested 6F6G last....

Alright...something just happened.

I put 6F6G in and tested. Not much changed. The 430V readings went to 429V and the other two changed to 7.31 VAC and .012 VAC respectively.

What happened was...as I was probing the first 429 V pin (3 I believe) the speaker made some static sounds then came to life! I tuned in a couple of stations but then after 30 seconds or so...it went dead again and probing the pin didn't repeat the Resurrection.

[morzh]

Dirty pins?

Did you wait for the tube to warm up before measuring the voltage?

If the voltage stays 430V (429V, no different) WITH the tube in, then either the tube is bad, or the socket is dirty, or the Cathode is not grounded.
Judging by it working briefly, my bet is on the dirty socket. Or loose pin.

[Tgace459]

Dirty pins?

Did you wait for the tube to warm up before measuring the voltage?

If the voltage stays 430V (429V, no different) WITH the tube in, then either the tube is bad, or the socket is dirty, or the Cathode is not grounded.
Judging by it working briefly, my bet is on the dirty socket. Or loose pin.

Yessir. I let it warm up and went back and retested it after the resurrection/death and get the same readings. I gave everything a good cleaning but Ill go back at it again and look at the pins. Is a loose pin as simple as a gentle squeeze of the socket with a needlenose?

[KCMike]

Yes that will work if you can get to them. Just be gentle with pressure. If that does not fix it and after trying Mike suggestions on speaker. You might try prodding with a wood dowel the various wire connections all around the underneath. Might have a loose connection or cold solder joint.