[TheUniversalDave1]

Thanks for all your help. I will definitely have a busy morning next Saturday. I'll replace the old capacitor blocks, the dogbone resistors, and check the antenna coil. Is there an easy way to tell the capacitance of those capacitor blocks? I assume a generic yellow capacitor will replace them with no problem. What will we do if the antenna coil is open?

[morzh]

Dave


If you re-read the thread one more time (not a bad idea) you might notice that at some point it was suggested the capacitor blocks have already been restuffed with the new caps, so why replace them?


I am referring to the backelite capacitor blocks. You do not necessarily need to repace them or measure them, just unscrew one of them, turn it over and see if it is still potted with black tar or there are newer, possibly yellow or brown, or maybe white capacitors inside. In which case you just leave them alone.

It is quite possible someone has done full recap for you already.

And without desoldering wires there may be (at least for some of them) no good way of measuring them.

Just pay attention to what people say here and don't get trigger happy. Take it easy. Enjoy it.

[Radioroslyn]

< Is there an easy way to tell the capacitance of those capacitor blocks?
There's two ways, you can read the diagram or some where on the phorum there is a list with the part # of each condenser with the value or values of the condenser inside. Some have two inside.

<I assume a generic yellow capacitor will replace them with no problem.
Yes as long as the voltage rating is high enough. Most new ones are 630v which are fine. If you are speaking of the little yellow mylars if you touch the yellow part with the solder iron chuck it you just shorted it out.

< What will we do if the antenna coil is open?
The same thing you'll do with the tickler winding on the oscillator coil if it is open rewind it. We can discuss when you have  sorted out the condensers. Like I said no worries there's a few steps to do in but it's not rocket science.
Terry
Diagram here: http://www.nostalgiaair.org/PagesByModel...013875.pdf

[TheUniversalDave1]

That's why I hate it when people restuff old capacitors. Cause sometimes it's hard to tell if they've been fixed!

[Joe Rossi]

Welcome Dave!

For the values and diagrams for the Philco block capacitors, see Chuck Schwark's website @ http://philcorepairbench.com/bblokcap.htm.  He also has LOTS of helpful information on Philco parts @ http://philcorepairbench.com/partinfo.htm.  His schematic service is without equal.  Keep us posted.  Joe

[Mondial]

Dave, don't be in a hurry to randomly replace parts without localizing the actual problem. 

As mentioned by others it appears that all the paper caps in the bakelite blocks have been replaced. It seems that the detector and audio stage are working properly, so why would you consider blindly changing parts without investigating further? A systematic, logical approach to troubleshooting produces better results and minimizes the risk of inadvertently creating new problems which did not exist before

Concentrate your efforts on checking the antenna and oscillator coils for open windings, and check the circuitry around the miixer/oscillator tube ( 1st detector ) as it appears that this is where your problem originates.

[TheUniversalDave1]

Well, it does have all the original dogbone resistors, which I have heard to be off tolerance by as much as 30%. I will be replacing those anyway. As for the capacitors, I would probably replace those restuffed or not. I hate old capacitors. I like being able to see the new capacitors so I can be sure that they have been replaced. I will definitely try to check the antenna coils.

[klondike98]

...well if you are really set on taking the bakelite block caps out (and I recommend you keep them in the set) don't throw them out! Put them up for sale in the "for sale or trade" section on the Phorum.

[TheUniversalDave1]

I checked the block capacitors, and they have indeed been restuffed with new yellow capacitors. I will not mess with them anymore. What should I do now?

I found a broken/loose wire while looking through the wiring. It comes out of one of the coils.  

[Mondial]

That's not a loose wire. Its a "gimmick" capacitor. It should be wrapped around the adjacent wire as it was in your original photo.

The unterminated wire provides a small amount of coupling capacitance across the antenna coil to increase sensitivity at the high end of the broadcast band. 

Before doing anything else, check the coils with an ohmmeter to make sure there are no open windings. Open windings in the ant or oscillator coils are probably the most common problems with this type radio.

[TheUniversalDave1]

With the volume control full on and the set unplugged, this is what I got.

[Mondial]

Does the resistance reading vary as you turn the volume control up and down? It should show the highest resistance when it is at the lowest volume setting.

The next thing  is to check the oscillator feedback winding. Find the 6000 ohm dogbone resistor ( blue body, black end, red dot ) This resistor is in series with the feedback winding of the osc coil. Measure either end of this resistor to chassis ground. One end should read almost zero ohms to chassis. The other end should measure around 6000 ohms. If you get an infinite ohms reading between both ends and chassis ground, then the coil winding is open.

[TheUniversalDave1]

The resistance did not change depending on the position of the volume control. What is the best position on the multimeter to read resistance in stuff like this? I'm not too familiar with the controls it has.

I will try that. I am actually in the process of converting my homework desk to a radio workbench. I'm going to get a simple tackle box and buy a few capacitors and resistors and heat shrink tubing and stuff like that. It's getting annoying only being able to work on radios 3 hours a week. This radio is now on Youtube.

[Radioroslyn]

Hi Dave
<I found a broken/loose wire while looking through the wiring. It comes out of one of the coils. 
You can see it on the schematic it's #3. It's connected to the antenna coil
I think if you adjust the volume control unless the coils it is open meter reading won't change much. The coil when good it's resistance is so low that it make the volume control look like a dead short.
GL
Terry

[TheUniversalDave1]

I tried measuring the blue resistor with a black end and red dot to ground, and on both ends I got 00.0 on the multimeter. It was in the Ohm 200 setting.