[Eliot Ness]

Maybe I should take the time to clean all the tube pins while I am at it.

That's a very good idea. Also look for any signs of arcing on the tube sockets, loose/cold solder connections on the tube socket pins etc. I have some very long, but small diameter brushes made for paint gun cleaning that are great to clean the tube sockets.

[Arran]

I think that it's time to break out the volt ohm meter and start taking some measurements, starting with the power transformer windings, first resistance readings, then AC voltage readings. After it's cleared then you can check the DC voltages on the tubes, and the resistance of the IF cans, and the coils. If all of these check out I would not waste any more time trying to troubleshoot the set, replace all of the paper and electrolytic capacitors, and any out of spec resistors, the chances are that the set was retired because it no longer worked. One common fault this era of Philcos seems to have is a failed output transformer, that may not be why the set does not play, if half the primary is still good it should produce some audio if you touch the grids of the power output tubes.
Regards
Arran

[morzh]

I say one should replace those regardless and before starting any work. I do not power up before I do it.

[murf]

Noticed there are a couple bypass caps(1000 volt) on the 42 tube sockets.
Looks like cap numbers 76 and 79 on the schematic. I can't read the values as the copy is really blurry.
I tried to read the value off the caps, but they are buried and of course the number I need is on the underside. Don't want to remove them till I have the replacements.
I will have to get a copy from Chuck if I can't find a readable copy.
Can anyone tell me what the values of these 2 caps are?
Thanks for all the help guy's.
I wish my tech skills were even 1/2 of what you guy's have.
Unfortunately, my forte ended up being tool and die making, which I enjoy as well.
Does not help me much on this stuff though.
Just a hobby and I learn as I go.
Gotta have something to do in retirement.
If I can get a readable schematic, I can start checking voltages and see if the tranny is up to snuff.
Have a great evening,
murf

[bfrohwein]

they're .003 mfd they are #76 and #79 I replaced them with .0033 1600 Volt "Orange Drops"

I have a clearer schematic. just a note on those.. I had a really bad hum after I replaced them. I ended up having to re-route the ground wire and make sure those two caps shells weren't touching the underside of the chassis. here's a link to a video that demonstrates that: http://youtu.be/CDk7EK0ytSc

you'll do just fine. I don't know Jack and I got mine running.. ;-)

[murf]

Wondering if someone knows of a simple way of testing the output tranny on this radio?
Getting no audio other than a very slight humm.
Output tranny does get warm after being powered up for a 15 minutes or so.
Thanks,
murf

[vinzer]

ohm meter center tap to both plates of output tubes should be about the same one will be a little higher should be several hundred ohms on each side of center tap.

[morzh]

You could, with the chassis unplugged!!! pull out the pushpull tubes and using either an audio oscillator capable of 10V or so, or isolation transformer with variac, couple the output starting from few volts between anode pins.
If you hear the sound or a buzz - you are good. Feeding the output to centertap and each end one at a time, if you hear the same volume sound/buzz you are good.

[murf]

Well guy's, here is what I found.
Replaced the 42 tubes only and checked center tap on the output tranny to both plates of the 42 tubes and got 632 ohms on one and 1.48 k ohms on the other.
This was done with only the 42 tubes installed.
Look like new transformer is needed?
murf

[morzh]

Murf

Are you sure you measured centertap to plates? Was the transformer unsoldered and soldered back again? Could it be you are measuring from one end to centertap and then to the other end?

PS. Which one is 43 tube?

[murf]

Typo.
Meant 42 tube.
I am measuring from centertap of output transformer and then I am assuming that the other 2 leads are to the plates on the 42 tubes.
One lead to centertap, and the other lead to the pin on the 42 tube that the wire is connected to.
Am I correct?
Nothing has been disconnected or unsoldered.
I don't the fancy equiptment or the know how to use it.
I have a multimeter etc.,so I have to keep it simple.
murf

[morzh]

Murf

It is theoretically possible to see results like yours, but I have yet to see it. Typically the DC resistances of two halves of the primary in the output pushpull transformer are of the same order. It is normal for the outer half to have a bit higher resistance for obvious reaons, but not double. Well, suppose they wound primary half, then output, then the other primary half...but I never saw it.

This is why I asked of you being sure - one resistance is almost twice the other which is the case when measuring end to end and end to CT.

Now, having mused about that, the best check is what I suggested with a Variac and isol. xfmr. This will give you a good reference. Then you simply measure the output with AC voltmeter.

So, you plug isol. xfmr in AC MAINS, plug your Variac in the Isolation xfmr and connect the output of say 20V across the CT and one end. Measure the secondary output. If it is too small, make input 50V. Then connect the input V across the CT and the other end.

The output should be exactly the same.

[Arran]

Murf;
Measure the resistance between the plat pin of each #42 tube and the center tap of the output transformer, they should be of the same resistance within about 5 to 10 ohms. Generally speaking if you are measuring a resistance between the plate pins on both output tubes then the transformer primary is good. It's very rare to have shorted turns on the primary of an output transformer, and even if there was some shorted turns the total resistance would be noticeably lower then it should be.
Regards
Arran

[murf]

Hi Arran,
Is the number 2 pin the plate pin?
Tube diagram on NA does not specify which is plate pin.
The leads from the output transformer go to pin 2 on each 42 tube.
If I measure resistance on the other pins I get about 360 ohms on those.
Am I doing it right?
Thanks
murf

[morzh]

Murf

yes #2 is the plate.

Question: do you look at the panel land count from the last fat pin (filament) clockwise?

http://www.radiomuseum.org/tubes/tube_42.html