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model 86 push pull xfmr - Printable Version

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model 86 push pull xfmr - btoher - 04-19-2020

Hi, Hope all are well out there ... I have been restoring a beat up old model 86 . Got all the caps changed out and voltages all
back to normal . I usually check things like transformers and speakers out before I get started . But missed that the primary of the push pull
was open. So I took it apart thinking it was most likely bad solder joint . But the problem was in a ways and so the coil is no good.
Question is does anyone know of a proper or close replacement for this ? I am thinking I can get it to work then wait to stumble
across an original some day . Then get it back to more original shape. I understand impedance is key , but all I have is what  think is 
the original resistances . They are 1500 ohms primary and 6000 ohms secondary which is center tapped to chassis . Thanks for any
help !!!
Bill

RE: model 86 push pull xfmr - Radioroslyn - 04-19-2020

https://www.tubesandmore.com/products/transformer-audio-interstage-10-ma

RE: model 86 push pull xfmr - btoher - 04-19-2020

Terry : Thanks for the link and info . I think that the coil version might even  fit in the original case . Or the  open frame
 version might look ok as is . I put some time in on this set and was stumped. And I am ready to hear it work again after
 being a step away from the trash pile . I appreciate the help !!!
Thanks!
Bill

RE: model 86 push pull xfmr - Radioroslyn - 04-19-2020

I've used the coils before and it worked fine. Was luckly in that some transformers the plates are interwoven. It's not a big deal but does require a little more time to get them apart and reassemble. The Crosley set I was working on had two sets of E plate end to end. Do make sure you core size is 1/2"X1/2" else it won't fit properly. https://www.flickr.com/photos/53710524@N06/10390988414/in/photostream/
GL

RE: model 86 push pull xfmr - gbreisdorf - 04-19-2020

This certainly is my lucky day!  I picked up a model 86 a few weeks ago and was a ways into the restoration when I discovered that the push pull xfmr had an open primary.  Had checked all other xfmrs and chokes but missed this one.  Joined the Phorum today, to see if I could get some answers and was 5 minutes on the site and discover this post!  Thanks guys. 

George

RE: model 86 push pull xfmr - btoher - 04-20-2020

The laminations on my Transformer have a 3/4" center . And the replacement coil has a 1/2" center. So I purchased the full frame version and not the coil .That is ok with me . I will see what I can do with it when it gets here as far as appearance . I will be happy if it works !!!
Bill

RE: model 86 push pull xfmr - Radioroslyn - 04-20-2020

Just for grins if you like to experiment a little w/the new transformer installed and the set working connect a small cap from the plate lead to one of the grid leads. I've done this to improve the frequency response on se amps in battery sets. In terms of values something like .005 to .01mfd voltage wise 100v is plenty. This may improve the hi and low frequency response. If it does make an improvement try adding another cap from the plate lead to the other grid lead. This may cause the amplifier to oscillate if so remove the 2nd cap.There are a lot of other factors in the equation so it may not make much of a difference.

RE: model 86 push pull xfmr - btoher - 05-01-2020

Hi, Just wanted to give a quick follow up on the transformer replacement . I got it yesterday and hooked 
it up quick . Turned on the radio and got a station right away . Works better than expected !  I was tuning in several stations last night . And was happy with how it worked and sounded . And to top it all off the transformer 
is really small .  It looks that the replacement transformer will fit in the original case without a problem. 
I am thinking I will just put this back together and call it a wrap . I may play around with the tone by adding
caps as suggested , but I am very happy with the outcome . It would not have happen without the help
provided here so I appreciate the help !!! I'll have to look for a  new project now . Maybe it will find me.
Stay safe and thanks  for all !!!
Bill

RE: model 86 push pull xfmr - Radioroslyn - 05-01-2020

Glad to hear you got the old guy percolating again!!