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Philco 84 code 121 no sound - Printable Version

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RE: Philco 84 code 121 no sound - Mike L - 11-11-2016

I have the primary winding and insulation strip removed from the antenna coil. What is the best way to clean off the residue/glue/wax off the coil in preparation for the new without damaging the enamel of the secondary?

RE: Philco 84 code 121 no sound - Radioroslyn - 11-11-2016

(11-11-2016, 07:13 PM)Mike L Wrote:  I have the primary winding and insulation strip removed from the antenna coil. What is the best way to clean off the residue/glue/wax off the coil in preparation for the new without damaging the enamel of the secondary?

Don't believe there's any glue there pretty much just wax. I just use a heat gun to gently warm it up and wipe off the excess wax with a dry rag.

RE: Philco 84 code 121 no sound - Mike L - 11-11-2016

Maybe its the varnish from the primary. There was wax, but also there are non-wax spots that are hard and chip off.

RE: Philco 84 code 121 no sound - Mike L - 11-13-2016

Well...I have the first coil wound. Measures out at 2.5 ohms. There were 21 turns on the old primary, so that's what I put on this one. The biggest problem was getting the insulating strip to stay in place and not open up on the ends. Not the prettiest job, but the first. Another coat of lacquer and on to the oscillator coil.

RE: Philco 84 code 121 no sound - Radioroslyn - 11-13-2016

Looks good and sure it will work fine.

RE: Philco 84 code 121 no sound - klondike98 - 11-13-2016

Nice job mike

RE: Philco 84 code 121 no sound - Mike L - 11-13-2016

Thanks. One thing that I did that may be helpful to others. My eyes are not what they were when I was 20 or even 40 (closer to 60 now) for that matter. in determining the number of turns needed, I tried the pin trick but sometimes it would skip over and not feel a "bump". So, by accident in taking the as found photos I realized I could zoom in the photo on my computer and clearly count each coil. I did this too on the coil after winding as well to make sure I didn't miss count. I picked the same spot in both before and after, right where the coil starts and square to the area of interest. Not sure if a cell phone camera would work as my digital camera has a macro setting which I really like for things like this.

Bob, really enjoyed your web page. I bookmarked it for future reference.

RE: Philco 84 code 121 no sound - klondike98 - 11-13-2016

great tip on counting windings...and thanks!

RE: Philco 84 code 121 no sound - Mike L - 11-13-2016

Before I start on the oscillator coil....are the number of turns and direction of those turns more important than the finished coil resistance?

The reason I ask this is the feedback winding has fewer coils (14-1/2 turns) than the antenna primary did and the resistance on the feedback coil is 2.3 ohms now. Once finally terminated the antenna coil came to about 2.3 ohms but has more turns. Both coil forms are the same diameter and I'm using 34ga. wire. Granted there is some corrosion on the feedback coil, but I do not have a reference for a resistance reading on this coil.

Am I over thinking this?

RE: Philco 84 code 121 no sound - Radioroslyn - 11-13-2016

> the number of turns and direction of those turns more important than the finished coil resistance?

Yes. The resistance is rather unimportant. What is important is the inductance, but not so much on this particular application. The the secondary is very important as it and the tuning cap determine the oscillator frequency. The primary (what you are rewinding) provides feedback from the cathode to the control grid causing the tube to oscillate. It doesn't have much to do will the frequency that the oscillator is operating at.

RE: Philco 84 code 121 no sound - Mike L - 11-13-2016

Its alive!!!....but still very faint and only receiving stations on the upper end of the dial. I can pick up a station 100 miles away but not WLW which is just 30 miles away. At least  it is receiving something.

I think I may have a volume control, potentiometer itself issue as well. After the antenna coil was installed I checked from antenna terminal to ground with my meter. It started to follow shaft movement but sometimes would go open or go way high in resistance not very linear.

RE: Philco 84 code 121 no sound - Radioroslyn - 11-14-2016

Sounds like it's time for a new one, or try a quick shot of wd40. Try not to get in in the switch section. As you may know it isn't a conventional volume control but a rf gain control hence it's a fairly low resistance like 15-20k w/sw which makes them a little hard to find.

RE: Philco 84 code 121 no sound - Mike L - 11-14-2016

I tried cleaning it with Deoxit, but no improvement. Looks like I need to find another. In the meantime cant I "bypass" it with a resistor to keep troubleshooting the remainder?

RE: Philco 84 code 121 no sound - Radioroslyn - 11-14-2016

(11-14-2016, 08:40 PM)Mike L Wrote:  I tried cleaning it with Deoxit, but no improvement. Looks like I need to find another. In the meantime cant I "bypass" it with a resistor to keep troubleshooting the remainder?

The vc doesn't do anything but vary the amount of signal from the ant to the primary of the ant coil. On some sets the vc is connected to the ant and cathode circuit which vary the cathode voltage this in turn effects the grid bias.

The short answer is yes you can and you don't need a resistor just a shorter ant or less signal from the sg when making adjustments. It's the same as using the set w/ the vc all the way up.

RE: Philco 84 code 121 no sound - Mike L - 11-14-2016

Ok I'll give it a try. The few stations received are very very weak, So I feel there is something else going on too. I ordered a set of tubes to see if I might not have an issue there as well.

As far as using the signal generator is concerned, am I measuring output to the speaker with my VTVM? I have the alignment procedure, but It just states adjust for peak signal, but where? I'm also not 100% sure my SG is working properly either. With it connected to the grid cap of the det-osc tube, SG set at 460kc all I get is a low pitched squeal around the 460kc and 1000kc spots on the tuning dial. Nothing anywhere else.