I.F. Coil bypass

[Geist]

Hi All;
I think I have a Bad Primary in my 1st IF coil.. I figure I have about three choices.. In no particular order..
1. Try my luck at unwinding it and hope it has a break near the end I am unwinding, and not at the other end.. I don't have a winding jig for these type of coils..
2. Put a cap of (to me) unknown value between the Primary and Secondary, Plate Primary to Grid secondary.. Like the Audio by-pass..
3. take out that If Transformer and associated tube, so that my Radio has a two Stage If Section, instead of a three stage If Section.. Untill I can find another IF can..
Can Anyone suggest the best way for me to proceed ??
THANK YOU Marty

[zeno]

What make, model & year is the radio ?
Also if you have a part # it may cross to a miller replacement.
No reason it cant be replaced somehow.

73 Zeno

[Geist]

Hi All;
Sorry, I didn't think at the time it was revelant..
My Radio is a Philco 34, Part number 32-1341 - - IF frequency 460 KHZ
THANK YOU Marty

[Einar72]

What is the diameter of the can? A Miller 312-C2 (has a round can) is a possible sub, also a Meissner 16-6601 windings-on-a wooden-dowel might fit, but, then, the dowel/coils from pretty much any 1930's input I.F will work; the Philco part has a goofy capacitor setup not seen in later years. Just be sure it's really open and not bad solder.

[Geist]

Hi All;
Einar, Thank You for looking this up.. Yes, they are round.. The cans are kind of strange in that they use a Large "C" ring, one on the Inside to help hold the Coil form in, along with the two nuts at the top.. And anothe Large "C" ring on the outside to hold the Can to the chassis.. The caps at the top of the Can are typical Philco of that era.. With a center screw for one adjustment cap and a nut adjustment for the other cap.. I have seen them in videos of others doing Philco Radio repair.. The Outside can measures 1 and 1/4 inches accross the top, accross the bottom it measures 1 and 3/8 and the coil form measures 1 and 1/4 and the inner coil stem that the coil is mounted on measures 1/2 inch..
THANK YOU Marty

[Username1]

Those things are so big, you should be able to take it apart and find the bad connection. Most likely at the connecting posts. Wire stretched, and not making a connection, hardly noticeable. Carefully take it apart and see....

[old_coot88]

When you find the break and need to strip the end of the wire so you can tin it, remember the 'aspirin trick' for stripping enameled wire, beginning at post#26...
http://videokarma.org/showthread.php?t=257295&page=2

[Geist]

Hi All;
I have taken it apart a couple of times, and the wire is not stretched as there is about an extra 1/2 inch at each end for just that purpose.. And I have had it in the light under a magnifying glass..
THANK YOU Marty

[Geist]

Hi All;
Well I have definately found out that the 1st IF Transformer is Bad, I wired up the rest of the front end.. I applied Power (no smoke, so not all is bad), and after much probing and adjusting..
I thought to check voltages on the 1C6 and I found out why the mixer was not working.. The plate voltage was 2.xx volts,, I rechecked that I had the wires were hooked up correctly and I also had it connected to +135 volts, which I did..
So the coil is bad, and in my checking, I found the secondary is now bad as well. so, while I look for another, I will try a couple of things, One is the two resistor cap hookup.. Would a 22K on the primary (Plate side) and 100K secondary (Grid side) with a 200 pf Cap inbetween work OK..
Another is I have a couple of If transformers from my AA5 parts bin and I will see IF I can make one of them work with de-tuning it, from 455Khz to 460Khz..
I figure it can't hurt to try..
THANK YOU Marty

[leadlike]

IF coils can go bad, like anything else. I had a sparton where that was the case. It had a unique center tapped secondary that I could not find a replacement for. Luckily, only the primary was bad, so I melted the wax on that coil, pulled it off and swapped it with a similar sized primary from another 460 of coil. Right away, it worked! The old primary was corroded open in many places. Maybe a humid day at the sparton factory allowed some moisture to be trapped that made that coil go open 80 years later.

[Reece]

Marty, I'm thinking you can transplant the coil assembly from one of your spares into the Philco can, using the Philco trimmers. It will probably tune 460 but if not, small silver mica caps could nudge the trimmers into range. Or in some cases you can remove a "leaf" from a trimmer to increase frequency. One way to try all this without getting into the radio would be to feed a modulated 460 from a signal generator into your good xfrmr and use a signal tracer with demod probe on the secondary to see if the device would peak. If no signal tracer then a germanium diode feeding into an audio amp.

[Geist]

Hi All;
I just ordered some coils, well see If they are of any help..
I hope I can use the Insides, even if the can is not the same..
THANK YOU Marty