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 Confused about this wiring

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OtakuN3rd

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PostSubject: Confused about this wiring   Thu Oct 14, 2010 9:39 pm

I've been putting this question off, but next to the tuning capacitor in my Philco Hippo (Model 49-900) there are two small wires that are not soldered on one end.



Its hard to see in the picture, but there is a green wire that is resting in the terminal on the upper part of the tuning capacitor then it is soldered to the third terminal from the left on that little board. There is no evidence that there was anything soldered to the point where it is resting on the tuning capacitor.

The other wire (it appears to be white) is soldered to the connector on the bottom section of the tuning capacitor and is wrapped around the leftmost terminal on the set of four. There is no evidence that the wire broke off from the terminal that it is wrapped around.

They are both really thin wires, like ones that would be used on a coil of some sort.

I can't tell where they would have broken off from, nor where they were supposed to go. Perhaps they were for an internal antenna?

Did this radio have an internal antenna? (If so, then its missing from mine.) If it is missing the antenna, is there any way I can make due without it by using an external? What about making up an new one?

I feel kinda stupid for needing to ask this, but I'm having a hard time following the schematic in this spot.confused

In other news I checked the resistors and found one out of tolerance, so I replaced it.
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marcc

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PostSubject: Re: Confused about this wiring   Thu Oct 14, 2010 10:58 pm

Cannot see it well.

One form of small capacitor consisted of a heavy central wire sometimes just insulated wire, others a ceramic tube. That had wire wrapped around the outside and quite often waxed to stop it comming off.

These were actually an adjustable trimmer.

Marc
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majoco



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PostSubject: Re: Confused about this wiring   Fri Oct 15, 2010 1:01 am

IMHO it's one of those "gimmick" capacitors - too small in value to be made from a normal variable trimmer, so it's made from just two wires twisted together..
Regards - Martin ZL2MC
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richfair

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PostSubject: Re: Confused about this wiring   Fri Oct 15, 2010 4:57 am

I don't have this radio, others here probably do, but it looks to me like your radio has been altered around that area. I looked up 49-900E, http://www.nostalgiaair.org/PagesByModel/669/M0013669.pdf

Based on the 900E, there should be a loop antennae somewhere, LA400 on the schematic, I would expect it to be mounted on the radio's back. Without a loop, I don't believe your radio will tune anything.

Your picture is a little fuzzy but I don't see capacitor C401. That was mounted near the chassis below the tuning capacitor. It connected to a secondary loop in the missing antennae to allow an external antennae connection. It would not be needed for local station reception but it is proof that someone has made alterations.

I think both of those unconnected wires are leftovers from the loop antennae that is no longer there.
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Reece

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PostSubject: Re: Confused about this wiring   Fri Oct 15, 2010 7:25 am

Your radio requires a built-in loop antenna to operate. These were usually attached to the inside of the cabinet back. If the back is missing, probably the loop is, too. The fine wires that you are describing may have gone to the loop.

A new back can be jigsawed carefully out of 1/8" masonite, available at home centers. Make a cardboard template, first. Cut adequate ventilating holes in the back, top and bottom. I attached a picture of a back that I made like that.

You can make a replacement loop antenna per the instructions in the attached link and after it is tuned, attach it to the new back. The instructions say to make about 35 turns and then attempt alignment per the instructions on the NostalgiaAir schematic. If the set won't align to the dial numbers then remove one turn from the loop and try again, and so on.

The loop attaches electrically to the stator (large section) of the tuning capacitor, and to the tuning capacitor frame.

You could also purchase a replacement loop antenna like the one sold by Antique Electronic Supply, on their website under the category Radio Parts & Restoration, Coils and Coil Forms. This would probably be the easiest way out. The backing on their loop wouldn't do for the full rear cover of your radio, but you could attach it on the inside of a cover that you make.

These "Hippo" radios are a lot of fun to look at and are good performers, too.

http://www.sparkbench.com/loopante2.html

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Bill Cahill



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PostSubject: Re: Confused about this wiring   Fri Oct 15, 2010 7:49 am

On Philcos the antenna loop is glued to the insideof the cabinet.
It wraps around all 4 sides.
Look in there.
Bill Cahill
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Reece

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PostSubject: Re: Confused about this wiring   Fri Oct 15, 2010 10:25 am

Bill wrote: On Philcos the antenna loop is glued to the inside of the cabinet.

Right you are, Bill, forgot about that! That would really solve the problem easily.

Reece
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OtakuN3rd

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PostSubject: Re: Confused about this wiring   Fri Oct 15, 2010 10:40 am

Ugh, I just had a long reply all typed out then I get a "no post mode specified" error.

Oh well, such is life.

Anyways, thanks for the help!

The internal antenna is gone, but those wires are in fact left over from the original, and I figured out where to wire a replacement to.

My next question is how do I know how many turns does the coil that is for the external antenna have?

The example at that website has a few of them on the inside, but doesn't specify how many are needed.

Just goes to show my inexperience, lol
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Don



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PostSubject: Re: Confused about this wiring   Fri Oct 15, 2010 12:50 pm

Sixteen laps around the back will do it.
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Reece

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PostSubject: Re: Confused about this wiring   Fri Oct 15, 2010 2:44 pm

Another idea some have used is multiconductor computer ribbon cable, if you have a source where they sell it by the foot. You can strip off as many conductors as you need and keep them in a ribbon. Then they are offset by one at the splice and soldered so that they make a spiral. If I were doing it that way I'd make it a few turns too big and then remove one by one if necessary to get it to align.
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OtakuN3rd

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PostSubject: Re: Confused about this wiring   Fri Oct 15, 2010 3:24 pm

That ribbon cable idea is a good one, I'll give it a shot. I have a tub fill of old IDE cables and some floppy drive cables that are really long, those have 34 wires in them.

I did attempt to make one like the article described, but it didn't turn out very well.

The capacitors for it came today, so I recapped it, soldered on the crappy antenna I made to try it out.

And... nothing, not even the dial lamp. I found a lose tube, reseated it, turned it on and it warmed right up.

Because my antenna is so crummy all I could pick up was one station, but its the only AM station I listen to anyways (WGTO). The volume is also quite low, unless I am touching the antenna. The volume goes up to what I would expect, but its practically nothing but static.

I'll try the ribbon cable around the cabinet next, but first I'll need to clean it up and fix the cracks.

I have a question about a substituted tube in it, but that is a different topic so I put it in it own thread.
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