Since there is no known source for replacement IF xfmrs, I'm thinking about building my own. But I need some advice before plunging ahead.

An IF xfmr has 1:1 windings, each shunted by caps to resonate at the IF, say 455 kHz. If, for example, each coil's inductance is 225uH and the caps are 545pF, then the resonant freq will be 455 kHz. (The caps are the easy part.)

Coils like this would involve >100 turns, and trying to wind them myself would put me in the looney bin, I fear.

AES sells 225-uH oscillator coils (Cat. No. P-76) for $1.95 each, which have a single winding on a cardboard form. I'm thinking about taking two of those coils, removing one from its form, and sliding it onto the other form, making a xfmr. Easier said than done, probably, but certainly easier than winding my own?

The caps would be just silver-micas of the appropriate value. For trimmer/tuning caps, I would try to get by with "gimmicks" (two insulated wires twisted together).

I'm looking for comments and suggestions. Thanks.

:Since there is no known source for replacement IF xfmrs, I'm thinking about building my own. But I need some advice before plunging ahead.
:
:An IF xfmr has 1:1 windings, each shunted by caps to resonate at the IF, say 455 kHz. If, for example, each coil's inductance is 225uH and the caps are 545pF, then the resonant freq will be 455 kHz. (The caps are the easy part.)
:
:Coils like this would involve >100 turns, and trying to wind them myself would put me in the looney bin, I fear.
:
:AES sells 225-uH oscillator coils (Cat. No. P-76) for $1.95 each, which have a single winding on a cardboard form. I'm thinking about taking two of those coils, removing one from its form, and sliding it onto the other form, making a xfmr. Easier said than done, probably, but certainly easier than winding my own?
:
:The caps would be just silver-micas of the appropriate value. For trimmer/tuning caps, I would try to get by with "gimmicks" (two insulated wires twisted together).
:
:I'm looking for comments and suggestions. Thanks.

Hi Doug,

You might want to take a look at http://geek.scorpiorising.ca/455KHz.html

Radiodoc

Hmmm, very interesting link. Thanks, Doc.

Doug,
First of all you'd have to have correct spacing of the 2 coils on the final form, for correct inductive coupling and final bandwidth of the IF response curve. You can cut the new coil form cardboard tubes and slide it onto another smaller tube duplicating the spacing of the original. Secondly, gimmick caps (twisted/insulated wire)will only provide a micromicrofarad (picofarad) or less. To do the kind of trimming (tuning) you'd need for a 455khz IF transformer, the gimmick cap would probably be useless, unless it was several inches long, and where would you put it inside an IF can. Gimmick caps were used years ago in VHF TV front end tuners, where very small capacitances were needed for neutralizing plate to grid of amplifier triodes etc, and typically were an inch or less. The mica trimmers inside these old IF cans can be duplicated with patience and persistence. If you insist on the mica, some surplus electronic warehouses may still have early power transistor insulating pads of mica in various sizes. Several insulating mat'ls are available, and equivalent in loss to mica. The methods and materials availability are endless. I envy your creativity and say "go for it"
marv

:Since there is no known source for replacement IF xfmrs, I'm thinking about building my own. But I need some advice before plunging ahead.
:
:An IF xfmr has 1:1 windings, each shunted by caps to resonate at the IF, say 455 kHz. If, for example, each coil's inductance is 225uH and the caps are 545pF, then the resonant freq will be 455 kHz. (The caps are the easy part.)
:
:Coils like this would involve >100 turns, and trying to wind them myself would put me in the looney bin, I fear.
:
:AES sells 225-uH oscillator coils (Cat. No. P-76) for $1.95 each, which have a single winding on a cardboard form. I'm thinking about taking two of those coils, removing one from its form, and sliding it onto the other form, making a xfmr. Easier said than done, probably, but certainly easier than winding my own?
:
:The caps would be just silver-micas of the appropriate value. For trimmer/tuning caps, I would try to get by with "gimmicks" (two insulated wires twisted together).
:
:I'm looking for comments and suggestions. Thanks.

Thanks, Marv, for your very nice and helpful comments! I appreciate your encouragement.

You're probably right, that the gimmick trimmers are a long shot. However, I was thinking of putting the gimmicks underneath the chassis where there would be more room than in the IF can - and would be accessible for tuning.

Also - Marv, your idea of cutting and slipping the two AES coils over a smaller form would make things much simpler.

If my gimmick idea can be made to work, then a 455-kHz IF xfmr can be built in about 20 minutes for about $5.00 (including the cost of coils and caps).

One more thing. I have an AADE L/C meter kit, which will measure inductance to 0.1uH: http://www.aade.com/lcmeter.htm

With this meter, I figure I could get the coil and the silver-mica cap matched to a fare-the-well, and thus minimize the required tuning range of the gimmick.

As far as I know, AES sells IF transformers. They also sell trimmers of various kinds. I don't know if they sell the compression type anymore. Inquire.

Thomas

:One more thing. I have an AADE L/C meter kit, which will measure inductance to 0.1uH: http://www.aade.com/lcmeter.htm
:
:With this meter, I figure I could get the coil and the silver-mica cap matched to a fare-the-well, and thus minimize the required tuning range of the gimmick.

Doug,

Instead of a gimmick why couldn't you mount a couple of two-position terminal strips close to the opening in the chassis where the IF leads pass thru. Connect the leads from each individual coil to the strips, connect the circuit wiring to the strips and then mount an appropriate trimmer cap across the strip terminals. Of course you would have to have the chassis out of the cabinet to adjust.

Radiodoc

Doug, Have you considered fixing the caps and tuning the inductances? For homebuilt it may be easier. Good luck and keep us appraised of your progress. Rick

Thanks for all your helpful suggestions.

I see that RadioDaze has a nice variety of NOS trimmer caps, both ceramic and mica, that should work; several sell for $0.75. I guess mounting trimmers under the chassis on a terminal strip would be better than my gimmick idea - and would be easier to tune than a gimmick.

Thomas, AES does have IF xfmrs, but they are the midgets that are for transistor radios. I've been told that they aren't suitable for tube-type applications, presumably because of voltage? They also have some regular-looking IFs, but they're 10.7 MHz.

Rick's slug tuning idea is a thought, too.

Doug,
I suggest that the original IF tuning elements were placed inside a can (shield) for good reason, and therefore should remain that way. Under the chassis or anywhere outside the can will not yield equal performance to the original. I also suggest that slug tuning, acceptable at 10.7 MC, may not work well at 455 KC, otherwise mfrs would have used that method years ago. Using dismantled 10.7 IF cores to re-assemble a 455 IF would require the use of different slug material to yield acceptable results. Small fixed dipped mica caps with appropriate voltage rating and a parallel variable would accomplish your goal, and still reside inside the can. Be mindful of the Q factor of both the inductor(s) and the caps. All winding methods and materials do not yield the same results.
marv

:Thanks for all your helpful suggestions.
:
:I see that RadioDaze has a nice variety of NOS trimmer caps, both ceramic and mica, that should work; several sell for $0.75. I guess mounting trimmers under the chassis on a terminal strip would be better than my gimmick idea - and would be easier to tune than a gimmick.
:
:Thomas, AES does have IF xfmrs, but they are the midgets that are for transistor radios. I've been told that they aren't suitable for tube-type applications, presumably because of voltage? They also have some regular-looking IFs, but they're 10.7 MHz.
:
:Rick's slug tuning idea is a thought, too.

Many AM IFs do have slug tuning. I own several radios with this method installed. It works quite well, and can be used at any frequency.

AES does sell 455 KC IF transformers, usually slug tuned, for tube type radios. INQUIRE! INQUIRE! INQUIRE!

These can be stashed inside of old IF transformers with the top slug protruding through the top of the old can, and the bottom slug accessable through a hole drilled in the chassis. Either this or you can first adjust the new units with the slugs so that the radio tracks properly. Then you can glue the slugs and remove the fixed caps from the new units. Connect the trimmers from the old units to the new units with the new units stashed inside. You'll be able to tune the new units just like the old ones. In some cases the trimmers for the old units may not be compatible with the new units. Experiment. You should normally get proper IF alignment when the trimmers are within the first three turns from tight. If you have to tighten them all the way, or the screw falls out because you've adjusted them too loose, you may consider readjusting the slugs for a compromise. A combination of the two should yield good results. Glue slugs once a position has been found where the trimmers adjust well within three turns from tight.

Thomas

OK, Thomas, I will INQUIRE of AES tomorrow. I hope you're correct, and if so I'll buy a half dozen or so xfmrs, and abandon my project for homemade IFs. Stay tuned.

Incidentally, here's three more questions regarding IF xfmrs - these have been answered before, but I can never remember the answers.

Receiver parts lists often have different part nos. for the first and second IF xfmrs, even though they seem identical by visual inspection. What's the difference, and is it really significant?

And, why does it make a difference which way you hook them up, e.g., a particular winding to the detector and the other to the IF amp? The leads are usually color coded to show which way they are supposed to go.

Finally: is phasing important? Does it really make any difference if, for example, the primary leads for the plate and ground are reversed? The leads are colored differently as if it's important. Why?

Doug:
I don't know the full answers to the questions you list below but here's something:
First of all... the primary's always have to feed plate current to the previous stage.... and the secondary windings only feed current to the grid of the following stages.
If you look at some schematics you'll see some differences from 1st to 2nd IFs.
Just look at the two IFs used in the Zenith 6d-525.

Zenith Print:
http://www.nostalgiaair.org/PagesByModel/095/M0025095.pdf

The first IF shows both that windings are 26 ohms while in the 2nd IF both are 37 ohms. Why?? Who knows?
Also you'll see some extra components in the 2nd IF can as well.
Note that these IF transformers are capacitively tuned as well.

Now.. It is VERY interesting that I took both these IF cans OUT of the Zenith 6d-525 and was able to put them into a Howard 901 chassis with great results!!

Howard print:
http://www.nostalgiaair.org/PagesByModel/368/M0009368.pdf

The Howard was using slug-tuned units originally... but these Zenith IFs worked just fine.

Now remember that the 2nd IF from the Zenith had those "other" components in there as you'll notice... but I just eliminated them and wired around them. Because the Howard schematic didn't call for them.
So this may all go to help you feel more comfortable with IF can swapping inasmuch as it doesn't seem overly critical to get a successful result by swapping.

:
:Receiver parts lists often have different part nos. for the first and second IF xfmrs, even though they seem identical by visual inspection. What's the difference, and is it really significant?
:
:And, why does it make a difference which way you hook them up, e.g., a particular winding to the detector and the other to the IF amp? The leads are usually color coded to show which way they are supposed to go.
:
:Finally: is phasing important? Does it really make any difference if, for example, the primary leads for the plate and ground are reversed? The leads are colored differently as if it's important. Why?

Different impedances affect bandwidth and gain and fidelity. Obviously a larger secondary is going to increase gain. It may lend too much mid-range passage to the audio. I know that if I take the IF cans out of a Zenith 6-G-601 and put them in a Sparton 7-36, the Sparton will work, and the IF transformers from one look like those in the other. The Zeniths are of higher impedance, giving more sensitivity to the battery powered radio. When used in the Sparton, stations tune deep down--bandwidth of Zenith IFs when used in the Sparton are narrow. Highs in the audio are missing.

I'm not sure about the reasons for the slight variations from coil to coil, and from primary to secondary, but I'm sure that the manufacturers had reasons for the variations--so that they'd get what they wanted out of the radio--if that much thought was given to that model of radio.

Regarding reversing leads, in some circuits this can affect unwanted feedback. The trimmers are sometimes connected so that the plate closest to the screw is on either the B+ or B- side so that capacitance coupling through your hands doesn't affect tuning much. Having this portion of the trimmer connected to either the plate or the grid lead would allow fluctuation in tuning due to the hand capacitance effect. Most trimmer screws are insulated by a disc of mica, but capacitance coupling is still possible through the mica.

Reversing the phase of the audio is not important unless some circuit relies on the phase being a certain way. If you play two radios next to eachother and they're out of phase, some of the audio will cancel. Usually we don't do this, though, and there's no way to tell for sure that the radios are in phase in the first place, unless the coils are examined.

Thomas

Lead reversal has an effect on all transformers, be they RF, IF, or AF. In some cases, however, the difference in performance may not be noticeable.

The standard practice that has been used since the year one is to keep the plate and grid leads separated as much as possible to reduce the capacity between them. On most transformers, this means that the plate lead will be on the outer end of the primary and the grid lead will be on the outer end of the secondary. This puts the B+ lead and grid return lead close together, where capacity between them is of little importance.

Bill is smart. Wish I had all that information up there. It feels good to soak it all up like a sponge. I wish I could pick the brain of an old Chevvy mechanic, too, or better yet, an engineer.

Thomas

:OK, Thomas, I will INQUIRE of AES tomorrow. I hope you're correct, and if so I'll buy a half dozen or so xfmrs, and abandon my project for homemade IFs. Stay tuned.
:
:Incidentally, here's three more questions regarding IF xfmrs - these have been answered before, but I can never remember the answers.
:
:Receiver parts lists often have different part nos. for the first and second IF xfmrs, even though they seem identical by visual inspection. What's the difference, and is it really significant?
:
:And, why does it make a difference which way you hook them up, e.g., a particular winding to the detector and the other to the IF amp? The leads are usually color coded to show which way they are supposed to go.
:
:Finally: is phasing important? Does it really make any difference if, for example, the primary leads for the plate and ground are reversed? The leads are colored differently as if it's important. Why?

Hi Doug,

Discussion about winding/rewinding coils got me to thinking I have an old coil winder "The New Modern Coilmaster by Moreco, Inc. stored somewhere for at least 30 years. After much searching found it. I decided to do a search on the net and came across a site that shows a picture of the original and a homemade replica. Just for kicks you may want to take a look. It is at http://www.qsl.net/k5bcq/COIL/COIL.html

Radiodoc

Radiodoc,
Thanks for the trip down "Memory Lane" I had one of the Coil Masters back in the 60's, and wound many AM IF and other inductors, and built a couple solid state radios from scratch. Wish I still had it, but don't even remember its demise. Maybe one of my many moves, East to West or West to East. I had to look at the picture just to remember the name. It was purchased from a surplus warehouse named "PolyPaks" Does anyone remember them? Are they still around?

marv

::OK, Thomas, I will INQUIRE of AES tomorrow. I hope you're correct, and if so I'll buy a half dozen or so xfmrs, and abandon my project for homemade IFs. Stay tuned.
::
::Incidentally, here's three more questions regarding IF xfmrs - these have been answered before, but I can never remember the answers.
::
::Receiver parts lists often have different part nos. for the first and second IF xfmrs, even though they seem identical by visual inspection. What's the difference, and is it really significant?
::
::And, why does it make a difference which way you hook them up, e.g., a particular winding to the detector and the other to the IF amp? The leads are usually color coded to show which way they are supposed to go.
::
::Finally: is phasing important? Does it really make any difference if, for example, the primary leads for the plate and ground are reversed? The leads are colored differently as if it's important. Why?
:
:Hi Doug,
:
:Discussion about winding/rewinding coils got me to thinking I have an old coil winder "The New Modern Coilmaster by Moreco, Inc. stored somewhere for at least 30 years. After much searching found it. I decided to do a search on the net and came across a site that shows a picture of the original and a homemade replica. Just for kicks you may want to take a look. It is at http://www.qsl.net/k5bcq/COIL/COIL.html
:
:Radiodoc
:

Thanks, Doc. I bookmarked that website.

:Thanks, Doc. I bookmarked that website.

Marv & Doug,

I was looking for something else at Lindsey Publications site and I came across a book on building a coil winder at http://www.lindsaybks.com/dgjp/djgbk/coil/index.html

Radiodoc

You know....I've never really given Radio Daze all that much of a look! I checked it out and it's pretty great. It is almost better than www.tubesandmore.com.

Thomas

:You know....I've never really given Radio Daze all that much of a look! I checked it out and it's pretty great. It is almost better than www.tubesandmore.com.
:
:Thomas

Hi Thomas,

I was impressed enough with Radio Daze I downloaded their catalog and printed it out. Printed front and back the thickness of the catalog is close to three-eights of an inch thick.

Radiodoc

I use both AES and RadioDaze, and both are satisfactory.

AES is more of a corporate-type operation, while RadioDaze has more the feel of a storefront. Internet ordering from RadioDaze is a little bit clunky compared to AES.

When they stock identical items, RadioDaze is usually a little cheaper.

Much of AES' catalog is devoted to electric guitar stuff, while RadioDaze is all antique radio.

AES' shipping seems to be a day or so quicker than RadioDaze.

For NOS and used tubes, RadioDaze is much more competitive than AES.

I liked the RadioDaze site too... esp the pots.. with the add-on switch-backs and the shaft coupler and long extensions. Very nice to know that its there.
I noticed that the miniature lamps are priced a bit high ($.45 each or so )like every other radio parts site,... but you all might like to know, if you don't already, that the lamps can be had as cheaply as 10 cents each!!! packaged in boxes of 10 at the pinball supply sites. I have purchased them here myself:
http://www.pinballlife.com/index.php?p=catalog&parent=3&pg=1

Doug:
Here's another intresting read on the subject:
http://www.electronics-tutorials.com/filters/if-amplifier-transformers.htm

I'd like to know why he thinks that cheaper radios have IF transformers. Wouldn't all radios have IF transformers? I would think that most modern radios still use the superheterodyne circuit.

Thomas

Thomas:
I think he means ... (talking to the uninitiated or un-aware student)...that they can EVEN be found in cheaper radios... ( meaning that they are very common and found everywhere...I think.)
...in his next article on Am Radios... he points out that (in Australia) it's wise for the radio student to find and collect cheap old AM transistor radios for class projects because the standard training kits to build them for formal class projects is about $54 U.S. bucks!!

:I'd like to know why he thinks that cheaper radios have IF transformers. Wouldn't all radios have IF transformers? I would think that most modern radios still use the superheterodyne circuit.
:
:Thomas

Interesting. Hopefully they don't go too far back. My grandfather had this really awesome Toshiba transistor radio that he used to listen to ball games on all the time. If he went to the stadium, he'd bring the radio along and listen to the game through the earpiece while he watched. It was one of the Toshibas that are really famous. I think my grandmother threw it away, though. She would throw everything away unexpectedly. She had a very clean house, but people lost a lot of stuff.

T.

:Since there is no known source for replacement IF xfmrs, I'm thinking about building my own. But I need some advice before plunging ahead.
:
:An IF xfmr has 1:1 windings, each shunted by caps to resonate at the IF, say 455 kHz. If, for example, each coil's inductance is 225uH and the caps are 545pF, then the resonant freq will be 455 kHz. (The caps are the easy part.)
:
:Coils like this would involve >100 turns, and trying to wind them myself would put me in the looney bin, I fear.
:
:AES sells 225-uH oscillator coils (Cat. No. P-76) for $1.95 each, which have a single winding on a cardboard form. I'm thinking about taking two of those coils, removing one from its form, and sliding it onto the other form, making a xfmr. Easier said than done, probably, but certainly easier than winding my own?
:
:The caps would be just silver-micas of the appropriate value. For trimmer/tuning caps, I would try to get by with "gimmicks" (two insulated wires twisted together).
:
:I'm looking for comments and suggestions. Thanks.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
What was the original IF transformers failure fault. Open primary or secondary and was it on one of the finish windings of a coil, or possibly the start….innermost connection of the transformer winding ? What was the case dimensions of the transformer. Is the winding on a cardboard form or plastic core ? Did it have two compression mica capacitors adjustments at the top of the housing? Or , perchance was it the newer ¾ in housing with the coil infrastructure encased in two coil enclosing powdered iron cups with a top and bottom slot for adjustments thru end access holes?
I have made my own larger case sized IF transformers for tube circuitry in the past. I opted for the easier coil solution of utilizing two 1 Mh RF choke coils,with their beautiful criss cross pattern of Litz wire making up the winding height. I initially took one coil and shunted it with my selected variable mica compression capacitor tightened to ~3/4 of its max cap. Then the outer winding was peeled off while constantly monitoring the LC combo with an adjunct Grid Dip Meter. When I hit resonance at 455 I stopped and then clipped the loose wire out of the circuit and then terminated the resultant outer winding to the cap to re check for any variance by the previous stray L and C elements of the snarl of loose wire.
Likewise, for the making the other coil....... and then the two coils were separated 1 inch with a 1/4 in hollow plastic tube that slipped over the coils solid bakelite winding cores. Additional plastic tubes over the outer ends of the coils provided room for my placements of two 3/4 in sq bakelite blocks that were drilled for the plastic rods to pass thru and my capacitors were mounted to the bakelite block. This resulted in a cap adjustment on the outer side of either coils, meaning that the tuning was done from 2 side holes in the shield, vice the common location of both being located at the end of a case. The coils leads were then routed to its companion SM var cap.
The shield housing was made from soldered together blank double sided copper PCB stock, 4 rectangular sides and a square top end with an open bottom with 6/32 two spade bolts pop riveted on the open bottom sides for chassis mounting. The top of the shield had a center hole that accomodated a pass thru 10/32 Nylon screw that threaded into an acrylic plug fused within the end of the previous constructed coil assembly.
As per the comments on the wire "gimmick" capacitors , they are to be of no use in a capacitance variance in the range that you are going to need for tuning.
The intercoupling spacing of the two coils will alter the bandwith characteristics of the constructed xformer. Closer for increased bandwith, with an accompaning increase of signal level coupling. Farther apart for a sharper and narrower bandwith response..along with a decrease in coupled signal. The spacing / coupling that I opted for was more in the order of a desired response on a broadcast AM radio. In Ham Radio use ...where a sharp selective tuning is desired, in case of an adjunt intefering station....... I have had up to two intermediately located coils with their precise tuning being accomplished with varactor diodes that were remote tuned via an adjustable DC voltage from auxilliary pots.
As far as detectying resonance of an L/C pair at 455 I will skip the other possibilities of use of a sig generator loosely coupled into the pair and monitoring with a scope or Diode detector probe into a VTVM/TVM/DVM.
Or using your "gimmick" tight wire coupling into a working tube receivers IF amp grid stage with the other lead of the coil to ground and then monitoring the AVC line of the receiver to detect when your L/C combo comes into resonance with the parasitic loading producing a variance to the AVC level.
But since you have a fiiine LCR machine to utilize, instead I will precalculate and give you the magic mathematic figure of 122353 for 455 khz . This will correlate with an expressed cap value in picofarads and inductance in uh. E.G., with a 815 uh coil divided into 122353 expect a capacitor of 150 pf to resonate close to 455. In my case it was a 611 uh inductance, as was peeled from that initial 1 Mh unit and then I found that ~ 200 pf was what I had the compressed cap set to in that ~3/4 max cap position initially.
Confirmation....... 611uh into122353----->200 pf.
Thassit.
73's de Edd
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Hey Doug:
Have you seen this device?
"IF or RF XFMR SUBSTITUTE"
....it seems that it is some sort of small sized substitute that you can mount under the deck to disguise it.
I have an email into the guy to ask him more about it.

http://www.dialcover.com/components.html

peter

That site is Bill Turner's. Confirm with him that they will work with tube-type radio voltages.

Doug:
Are you saying that you want me to pass along to him that you have found that they WILL work with tube voltages?... or do you want me to ASK him to confirm IF they will?... lol

He hasn't returned my email yet but that was my first question to him.
Peter

:Doug:
:Are you saying that you want me to pass along to him that you have found that they WILL work with tube voltages?... or do you want me to ASK him to confirm IF they will?... lol
:
:He hasn't returned my email yet but that was my first question to him.
:Peter

Peter,

It would be nice to see a picture of the device too.

Radiodoc

All I got out him so far was this:

"IT A MODULE HAVING FOUR COLOR CODED LEADS. IT IS A TRANSFER SYSTEM THAT
DOES NOT USE A TRANSFORMER."

(His short answers are because of his stroke)

I've asked him these questions today:

1.) Does it operate with tube voltages normal to the old radio IF transformers.. esp on the plate/primary side?

2.) also if it isn't using a transformer what is it? Is it simply an R-C coupling device of sorts?

3.) Will it tune to 455kc or 460kc as needed to behave as a filter?... or isn't it a tunable device?

4.) If it is not tunable does that mean you'd loose the narrow tuning selectivity that a standard IF transformer allows?...

:All I got out him so far was this:
:
:"IT A MODULE HAVING FOUR COLOR CODED LEADS. IT IS A TRANSFER SYSTEM THAT
:DOES NOT USE A TRANSFORMER."
:
:(His short answers are because of his stroke)
:
:I've asked him these questions today:
:
:1.) Does it operate with tube voltages normal to the old radio IF transformers.. esp on the plate/primary side?
:
:2.) also if it isn't using a transformer what is it? Is it simply an R-C coupling device of sorts?
:
:3.) Will it tune to 455kc or 460kc as needed to behave as a filter?... or isn't it a tunable device?
:
:4.) If it is not tunable does that mean you'd loose the narrow tuning selectivity that a standard IF transformer allows?...
:
:
Peter,

Just a wild guess...could it possibly be a ceramic filter with appropriate input and output circuitry?

Radiodoc

:Just a wild guess...could it possibly be a ceramic filter with appropriate input and output circuitry?
:
:Radiodoc

Well Doc... wouldn't that be nice...yes indeed.
..I would love that if it's true!
But it could just be some broadly tuned rc coupling device... I don't know... but for $4 bucks...do you think it could be anything that technically capable?
I'm anxious to hear from him.

Sounds like an R-C coupling. If so, it might be OK for replacing one IF xfmr, but no both. There would be somewhat less selectivity if the thing isn't tunable.

Yes Doug... that's what I was thinking too... and in fact here's Bill's answer... you are right!

"IT IS A NON-TUNEABLE MODULE, MADE TO BE INSERTED IN THE CIRCUIT IN LIEU
OF THE TRANSFORMER. ONE MODULE PER RADIO MAY BE INSERTED IN A RADIO
WITHOUT ILL EFFECT, TWO WILL CAUSE BROADBAND EFFECTS"

Here is Norm Leal's article on bypassing bad IF xfmrs with an R-C coupling ckt: http://antiqueradios.com/chrs/journal/transformers.html

The article assumes that just one winding, either the primary or secondary, is bad - in which case, leave the good winding in the ckt for tuning purposes.

If both windings are bad, then just follow Norm's suggestions, and it should work OK, but maybe with some loss in selectivity. I think this is what Bill Turner's IF-replacement gadget consists of.

Yes.. I followed that RC-coupling fix for my Howard 901A and it certainly worked...
But the Howard 901A had BOTH IF cans bad... and the RC-coupling when used in both IFs does tend to be too broadly tuned.

Doug:
Without going back through this entire thread here... did anyone direct you to this site? :
http://geek.scorpiorising.ca/455KHz.html

I may get around to trying it one day myself.

Another article somewhere I read suggests to use a small hand-crank drill... calculate the turns ratio of the handle versus the turns of the bit ( usually 4:1 ) and then divide that into the number of turns for your coil.
So as in the top article example for a 455kc coil ..a 250 turn coil would only require 62.5 turns of the handle... not bad.

For right now.. I am also experimenting with having that fellow Indalecio from Brazil...rewind a couple of bad IF cans (I pulled out of an old Howard 901A) that I still havelaying around here. I had already replaced them with IF cans I removed and repaired from a Zenith 6d-525 that got destroyed in a fire. Those cans worked out perfectly.

Anyway..Indalecio seems confident that he can do it well.
The mail will cost at least $5-8 each way alone... so I don't know how practical this may be for the long run... but if it works and you don't have anything else... then it's worth it no?

:Doug:
:Without going back through this entire thread here... did anyone direct you to this site? :
:http://geek.scorpiorising.ca/455KHz.html
:
:I may get around to trying it one day myself.
:
:Another article somewhere I read suggests to use a small hand-crank drill... calculate the turns ratio of the handle versus the turns of the bit ( usually 4:1 ) and then divide that into the number of turns for your coil.
:So as in the top article example for a 455kc coil ..a 250 turn coil would only require 62.5 turns of the handle... not bad.
:
:For right now.. I am also experimenting with having that fellow Indalecio from Brazil...rewind a couple of bad IF cans (I pulled out of an old Howard 901A) that I still havelaying around here. I had already replaced them with IF cans I removed and repaired from a Zenith 6d-525 that got destroyed in a fire. Those cans worked out perfectly.
:
:Anyway..Indalecio seems confident that he can do it well.
:The mail will cost at least $5-8 each way alone... so I don't know how practical this may be for the long run... but if it works and you don't have anything else... then it's worth it no?
:
:
Peter,

I believe I made mention of that back in my post of 1/24/06. It was interesting reading though.

Radiodoc