[Ronin61]

Terry thank you very much for the tip about odorless mineral spirits it worked great and my original dial scale looks very good. I will post a picture of it soon.

[Ronin61]

New dial scan printed on vellum which is more transparent than regular paper. With led illumination. Not the best photo but you get the idea.[Image: http://i1281.photobucket.com/albums/a508...51fe08.jpg]

[Radioroslyn]

Looks good!!! Just cleaned up one myself for 116. Boy I couldn't believe all the dirt that came off of it. It also has a crack in it. I've found that taping it from the back side with some clear packing tape works wonders and is pretty invisible. Also if you don't like the color so much you can put a little bit of water base paint on the bulb to tint it a bit if it seems too bright or too yellow or whatever.
GL
Terry

[Winky Dink]

I'm bringing this thread back to the top because one of the photos above illustrates my situation/question. Last summer I picked up a rusty, rats-nest Model 645X, run 3. As received, the wiring on the tuner rotors was as shown in the left photo. It shows a wire connecting the detector and oscillator rotors, just as shown in a photo earlier in this thread.

[Image: https://lh5.googleusercontent.com/-5BVoF...520645.jpg]

This appears the same as in post #8 above, but the connection is not shown in the schematic. Actually, in my case, the wire was not soldered to the oscillator rotor terminal--it was just sticking through the hole. I finished a satisfactory electronic restoration without the questionable rotor-to-rotor connection. But I'm still concerned I've missed something functional.

Does anyone know what this extra wire is for?

Grateful for All Advice,
Winky

(I also have to give a public "Thank You" to Chuck Schwark who provided the information which enabled me to rescue this radio.)

[Mondial]

That wire which passed through the terminal but was not soldered was actually a very small capacitor. It is sometimes known as a "gimmick" cap.

Evidently the Philco engineers found that the radio worked better with a small amount of capacitance between the two tuning stators and added the wire to provide that very small value.

Most likely it will not make a big difference, but you may want to reinstall the wire through the terminal as it came originally.

[Winky Dink]

I'm amazed to get such a specific reply. I guess I came to the right place. I rewired 99% of the set and discarded the old wire.

So this was an ordinary copper wire with the insulation, fabric, and air as the dielectric? I don't intend to replace it--just curious.

I greatly appreciate the answer. Thanks.
Another question to follow soon.
Thanks,
Winky

[Winky Dink]

Is everyone tired of questions about shadow meters? Well, I'm going to try one, anyway. My meter works pretty well; but with power on, the vane's no-signal position (the detent position?) is not centered. It remains somewhat left of center, and it deflect only to the left. With power off, the vane goes back to dead center. I'd like to look into the section with the coil, but I'm not sure how to do it without risking at least esthetic damage to the device.

[Image: https://lh6.googleusercontent.com/-SPL3E...520645.JPG]

I see six tabs in front, the "a's & b's," two side-slots at the rear, the "c's," and one tab, "d," at the back. It looks like there's a slot at the rear to pry and lift the upper case and possibly rotate forward, but it doesn't budge with gentle force.

So, is the vane supposed to deflect bilaterally? Is there anything I can fix to correct the centering? And finally, how the heck do you crack this thing open?

[Mondial]

There is nothing really wrong with the shadowmeter box itself. The problem is the position of the lamp filament in relation to the hole in the back and the vane.

The original bulbs had a filament location closer to the lamp base which was properly positioned with regard to the hole. Modern replacement bulbs are different and the filament is rarely in the right place. You may have to go through quite a few bulbs until you find one which will center the light beam over the hole. Alternately you may have to bend the lamp bracket for best alignment to center the shadow.

[Winky Dink]

I understand what you're saying. The bulb is actually an old one that came with the set. I have tried bending the bracket, too.
The vane snaps back to dead center when the set's turned off, but with power on, it doesn't return to the center position. I'd give you a photo, but the radio just had a catastrophic failure--sudden complete loss of audio, and it'll take me a while to sort that out.

Something I just thought of--when I first powered up the set, the vane moved left and stayed left. There was a 4.5Kohm dog bone shunting across the meter. Through experimentation I found that with a 490 ohm shunt the meter stayed centered. Right now I have no shunt. When (if?) I get the radio working, I'll try putting the shunt back in.

Thanks much for the reply.

[Mondial]

Shunting the meter reduces its sensitivity so its deflection is reduced. For maximum sensitivity you really want no shunt.

Do you get any deflection when the set is first turned on before the tubes warm up? There should be no deflection until the tubes start drawing plate current, which causes the shadow to widen. If you are getting any deflection at all on initial power on, then something like a leaky bypass cap is drawing current through the meter. You can remove the RF and converter tubes to see if any other load is causing the current through the meter.

[Ron Ramirez]

Original shadowmeter bulbs were made with a straight filament to make the shadowmeter work better (i.e. easier to center the shadow). Replacement bulbs have curved filaments, so as Mondial said, you have to make do as best as you can.

[Winky Dink]

Let me first apologize for misstating my shadowmeter issue. The vane remains slightly deflected with MAXIMUM signal. I can bend the light bracket to center the shadow, and the shadow will narrow substantially with tuning-- it just won't be at minimum width unless the vane centers perfectly when tuned accurately.

I was going to illustrate that with photos, but unfortunately the radio went tango uniform last night (any Air Force folks out there?). No audio--no apparent signal.

Nevertheless, here's a 20-second video of the shadowmeter. Power starts when the light comes on, the vane deflects maximum left and then returns slightly towards center. The vane remains in the position it is when the video stops. This is with no shunt, no antenna, and no apparent signal. I think this is normal.

https://picasaweb.google.com/coldrb/Febr...directlink

Now, to get the radio working again. While doing nothing but turning the tuner knob, the radio went silent. Nothing but a slight hum out of the speaker. No evidence of any signal received or amplified.

I have only a rudimentary understanding of electronics, but I did my best to diagnose until 2 a.m. The only anomaly I have found is the 6A7 oscillator/detector shows zero voltage at the oscillator grid. All other tube socket and power transformer voltages are the same as before the set died

I have double-tested the 6A7 with both transconductance and emissions tester; verified the appropriate continuity through the input transformer, output transformer, oscillator transformer; and randomly tested a number of other components. As you can see, I'm now flailing aimlessly at the problem and need some direction.

So, given the sudden failure and zero oscillator grid voltage (It was -22 V), can someone give me some direction in diagnosing the problem?

I have a legible schematic posted here:

https://picasaweb.google.com/lh/photo/gv...directlink

Grateful for Guidance,
Winky

[Winky Dink]

Update. I hooked up the long indoor antenna, and I do get some reception--weak and jumbled, as if it was desperate for alignment.
Maybe something happened to the RF or IF? Again, I don't know what I'm doing, but I'll see what I can figure out with a signal generator and check all the parts that I think are important in RF/IF detection, mixing, etc. But that will have to wait until tomorrow night.

[Winky Dink]

Volume Control--Can I disassemble it? I have the cabinet finished, but before the chassis goes in, I'd like to know if I can repair the volume control. It has one annoying dead spot--probably where it was set during it's years of disuse. This is part 33-5113 combination on/off and volume. I've had limited success in repairing a couple of volume rheostats, but I'd prefer to leave this one alone rather than risk further damage.

Does this control have a wire-wound resistive element? How difficult would it be to open the case and then reassemble it?

(Incidentally, relevant to my last post, the problem was just a bad connection to a tube cap.)

[codefox1]

The output 42's should work well enough even if testing on the weak side. When they start putting out more heat than audio, try to find a better set. Not all that rare or expensive. I don't have any, if I did would donate for postage.