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Philco 84 - Printable Version

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RE: Philco 84 - Radioroslyn - 04-09-2012

(04-09-2012, 09:56 AM)Jim Dutridge Wrote:  
(04-08-2012, 04:58 PM)7estatdef Wrote:  
(04-08-2012, 11:08 AM)Jim Dutridge Wrote:  Well now I'm bummed. The oscillator coil has both windings open. This will take some patience.

Are you sure? You know one of the lugs is a dummy. Use your ohm meter with one lead connected to the bracket, the other touch to the lugs. If the coils are good should show resistance on two lugs. If it show resistance on one probably the feedback winding is the open one. Never seen one with both open. Is a first time for everything.
Terry

Yep, both coils read open to the common lug. I unwound them and both had the dreaded green disease. Primary is a 17 turn winding while the secondary is a 93 turn winding. The open in the secondary was about 60 turns in.

I did have that problem with a model 600 awhile back. It was a pain as the wooden form on that set is about half the diameter of the 84. Ron's sez most of those coils are wound with 38G wire. That darn stuff is pretty small. To wind that coil I ended up using two pair of reading glasses and a luxo lamp..
Have Fun!
Terry



RE: Philco 84 - Jim Dutridge - 04-09-2012

Not sure what gauge wire I'm using. I pulled off an old Majestice field coil. Its pretty thin, and yes, let the fun begin. I do have some 40 gauge and 34 guage. Which would be better choice and would I just match the original number of turns with either?

RE: Philco 84 - Radioroslyn - 04-09-2012

(04-09-2012, 02:19 PM)Jim Dutridge Wrote:  Not sure what gauge wire I'm using. I pulled off an old Majestice field coil. Its pretty thin, and yes, let the fun begin. I do have some 40 gauge and 34 guage. Which would be better choice and would I just match the original number of turns with either?

Well the 34 would be a bit easier to work with. I would add a few extra turns to makeup for the size difference. Make sure that you wind it in the same direction as the original else it won't oscillate.
Terry



RE: Philco 84 - Jim Dutridge - 04-10-2012

I decided to go with the 34 gauge since it seemed closer in diameter to the original. I'm now 80 turns into the original 93 turn winding but still 9/16" away from the original length. My question is do I stop at the 93 turns or do I fill it up to the original length? Also, what about the primary side?

The original windings did have a small space between them but that was not possible for me to repeat, so the windings are now laid next to each other.

RE: Philco 84 - Radioroslyn - 04-10-2012

Hey Jim,
You aren't going to like my answer but what I do when there is a space between the turns is I lay down two windings side by side. One is the inductor and the other is a spacer. Once the coil is wound the spacer winding is removed.
You can leave yours as is but I'll bet that the set won't track properly and It will be low in frequency because your coil is going to be too high in inductance.
As for the feedback winding (small winding) I don't think I've ever seen one that has space between the turns. It's just would one next to the other. Just wound one up for a member the other night.
Fingers cramping yet???
GL
Terry

RE: Philco 84 - Jim Dutridge - 04-11-2012

I decided to take your advice Terry and unwound my original. Now I'm starting over with the spacer winding. YEA, my fingers are cramping. Thought I'd share how this is being done. My winder is an old hand drill, crude but works with some patience. 20 turns so far.

[Image: http://i248.photobucket.com/albums/gg187/jdut123/CoilWinding.jpg]

RE: Philco 84 - Jim Dutridge - 04-15-2012

Finally finished the secondary winding using Terry's idea of laying 2 wraps at once. I was only abl to get 85 turns versus the original 93 but I think it'll work. Now, how to go about putting some beeswax on it, brush it on or dip it?

[Image: http://i248.photobucket.com/albums/gg187/jdut123/Coilwinding001.jpg]

RE: Philco 84 - Radioroslyn - 04-15-2012

(04-15-2012, 12:18 PM)Jim Dutridge Wrote:  Finally finished the secondary winding using Terry's idea of laying 2 wraps at once. I was only abl to get 85 turns versus the original 93 but I think it'll work. Now, how to go about putting some beeswax on it, brush it on or dip it?

[Image: http://i248.photobucket.com/albums/gg187/jdut123/Coilwinding001.jpg]

First off Nice Job!! I would brush it on and use a heat gun to melt it and get it even. Looks like you've still got some space at the top of the form to wind a few more turns on. May have to drill a hole to run the wire though.
Terry


RE: Philco 84 - Jim Dutridge - 04-15-2012

Quote "Looks like you've still got some space at the top of the form to wind a few more turns on. May have to drill a hole to run the wire though.
Terry " Quote

Now why the H**l didn't I think of that.

RE: Philco 84 - Jim Dutridge - 05-11-2012

Well, after rewinding the antenna and oscillator coils I brought it up slowly on the variac and got nothing but 60 cycle hum at 60 VAC in. Dummy me forgot to connect the negative of the filter cap to the center tap.

`Fixed that problem but now the radio is deadly silent. At 90 VAC in I would expect to hear some noise but all I get is a faint hum thru the speaker. B+ looks good at 240 volts at the 42 plate and 205 volts at the 1st detector plate. Checking the oscillator I get +18 volts at pin 4 of 1st detector to chassis and +29 volts to B-. I swear I rewound that coil correctly. Can rewinding it the wrong direction cause these kind of readings?

RE: Philco 84 - Radioroslyn - 05-13-2012

Not sure what voltage is on the suppressed grid but the direction doesn't matter as long as there the the same, both windings tuned circuit and feedback. Where's the feedback winding? Don't see it in the pic's
So is the IF and audio stages working?
Terry

RE: Philco 84 - Jim Dutridge - 05-15-2012

This thing is ticking me off. Lets start from the beginning. When I first rewound the coil I wound the secondary in a CW direction from the common point and the primary in a CCW direction. No oscillation. Attaching a 4.7K resistor across the 6K, as suggested, did nothing.

Removed the coil and found a cut in the secondary and repaired it. Rewound the primary in a CW direction, even gave it 2 extra turns, and retried. Still nothing. Tacked in the 4.7K resistor and still nothing. The "gimmick" is in place and the wiring is correct.

I do have noise/squeal, whatever, thru the speaker as I bring finger close to the grid of the 77 second detector. I just tried sending a 460KC thru the radio with the generator set on high output using a AM loop placed close to the chassis and nothing. Checking the IF transformer shows all connections/ continuity is good.

Using a transistor radio I tried checking for an oscillator with the transistor radio set around 700KC and turning the tuning cap of the Philco. Nothing. I've already gone trhu and resoldered all connections including redoing all the ground connections off of the tube socket rivots and the B+ is good. All caps and resistors have been replaced.

I got my 77 tubes from a fellow ARF'er and they checked good on my tube tester. I even tried swapping them around in the radio and that proved pointless. I did ask for a picture of the underside of the chassis which I was kindly supplied but now that I actually pay attention to it the picture shows that all the tube sockets have been replaced with octals so who knows what the actual wiring should look like.

I'm kinda stuck here and need a good clear picture of the underside of an umolested 84 to compare with and also any advice of what to try next.

RE: Philco 84 - Jim Dutridge - 05-31-2012

Back to this 84. I can now get the IF thru the radio but nothing when it comes to sending a 1500KC signal thru as stated in the Riders for alignment. Does this radio use rubber gromments on the tuning cap? I have none on mine.

RE: Philco 84 - Radioroslyn - 05-31-2012

Nope. Usually used on set with avc to insulate the avc voltage from the chassis. Is the local oscillator working?
Terry

RE: Philco 84 - Jim Dutridge - 05-31-2012

Would appear so since I read a -4.2 volts from the control grid to the cathode of the 77.