I have 2 Crosley Trirdyns with both transformers in both radios bad. What is the impedence of these transformers and what is the resistance of them? I get about 465 ohms on one winding and that is it!
Will the coils sold by AES work in these? Denis

Denis, those 1:3 all-purpose audio interstage xfmrs should work.

The AES xfmr (Cat. # P-T156) sells for $15.70, and is generic, made in Mexico. RadioDaze sells a genuine Hammond (HX124A) for $12.69.

Hi

PTOP has A-53 without a center tap for $8.00. It's their part number 1017-001:

http://www.oldradioparts.com/2a23cfl.txt

Norm

:Denis, those 1:3 all-purpose audio interstage xfmrs should work.
:
:The AES xfmr (Cat. # P-T156) sells for $15.70, and is generic, made in Mexico. RadioDaze sells a genuine Hammond (HX124A) for $12.69.

Denis, you may have another option, but it may not apply to your Trirdyn. However, the following may be of benefit to others reading this forum, especially to the owners of earlier Crosley sets.

If your transformer iron will take a coil with a ½” X ½” window, then buy just the coil and use your original iron. These coils fit several other Crosleys, but I don’t remember if they fit a Trirdyn. If the coil fits, it won’t save much money, but the original mechanical fit in your radio will be preserved. These coils are also available at AES and Radio Daze.

These small replacements, be they just the coil or complete transformer, will work in many early battery sets, but they do not usually work as well as the originals. Although they are 3:1 ratio, the complete transformer has less iron and the coils have fewer turns. I have heard a considerable difference when comparing these replacements with original Crosley transformers of certain models.

A more expensive transformer such as the P-T124B from AES works about the same as an original, but the coil from this one will not fit the original iron of some Crosleys. Therefore, different mounting holes, etc. may be necessary if the new iron is used..

There is a way around this dilemma with some Crosley iron. It just so happens that two of the small coils connected in series will fit exactly on the original iron of these particular models. This increases the number of turns enough to better match the impedance involved, and they sound about the same as the larger replacement. But then, the total cost is about the same as the better one, so it becomes a matter of what will best fit your radio and how much you are willing to spend.

:Denis, you may have another option, but it may not apply to your Trirdyn. However, the following may be of benefit to others reading this forum, especially to the owners of earlier Crosley sets.
:
:If your transformer iron will take a coil with a ½” X ½” window, then buy just the coil and use your original iron. These coils fit several other Crosleys, but I don’t remember if they fit a Trirdyn. If the coil fits, it won’t save much money, but the original mechanical fit in your radio will be preserved. These coils are also available at AES and Radio Daze.
:
:These small replacements, be they just the coil or complete transformer, will work in many early battery sets, but they do not usually work as well as the originals. Although they are 3:1 ratio, the complete transformer has less iron and the coils have fewer turns. I have heard a considerable difference when comparing these replacements with original Crosley transformers of certain models.
:
:A more expensive transformer such as the P-T124B from AES works about the same as an original, but the coil from this one will not fit the original iron of some Crosleys. Therefore, different mounting holes, etc. may be necessary if the new iron is used..
:
:There is a way around this dilemma with some Crosley iron. It just so happens that two of the small coils connected in series will fit exactly on the original iron of these particular models. This increases the number of turns enough to better match the impedance involved, and they sound about the same as the larger replacement. But then, the total cost is about the same as the better one, so it becomes a matter of what will best fit your radio and how much you are willing to spend.

Thanks for the info. The iron is 1/2" by 1/2", so the coils will fit the iron. Do you connect both primaries and both secondaries in series to then give in effect double the number of turns for each winding? I'm not too cost conscious on this thing anymore, considering what I've already spent! Looks good though! Now just have to build a power supply. Denis

Sounding good so far Denis. Now you need to make certain that your iron will accept two coils. These coils are almost 7/8” in length, so if your iron has a 1 ¾” opening or more, then two will fit. I should have stated this in my previous post, but didn’t think of it.

Yes, you connect each primary and each secondary in series to give double the number of turns for the transformer. For the primary, this will mean connecting one red wire to a blue wire. The remaining red wire goes to B+ and the remaining blue wire usually goes directly to the plate on most sets. However, the Trirdyn is a reflex set, so you need to connect the blue wire as required.

The secondary has a black wire for a center tap, but you will not use it on either coil, and can cut them off if desired. This leaves two green wires on each coil, but they are not labeled. In theory it makes a difference which way these wires should be connected when using a single coil without the center tap, but you probably would not be able to hear a difference. When connecting the two coils, just do what looks natural and it will probably work ok. Just for grins though, you may want to swap the leads around while testing your set and listen for a difference.

Since you will be using two of these transformers, measure the resistance of all four primary windings before you connect any of them together. There probably won’t be much difference in them, but pick the two with the highest resistance. Connect them together and use this primary for the detector tube. A vacuum tube has a higher plate resistance when used as a detector, so it is always best to use the highest impedance primary when following this tube, regardless of the turns ratio. Of course, the next stage needs a high impedance too, and this is one of the main reasons why the series coils work better than a single.

There are different models of the Trirdyn with slightly different circuits. Yours may be exactly like the one shown in Riders, but it may not be. Years ago I drew a Model 3R3 that may or may not be closer to your radio. Just in case it is, I put a copy of it on the web. It’s a low resolution copy to keep the file size small, but will print out well enough for you to use if need be.

http://www.imswebs.com/br/3r3.pdf

Thanks for the great help! My Trirdyn is almost exactly like the one in Riders except for bat/fil/rheostat connections. I will get coils on order and go from there. Thanks again! Denis