Morrow Modulation Transformer...

[k6jca]

Well, I think I've discovered why my Morrow 565 is light on modulation -- from measurements I've made (and I've made many!), the most likely explanation is a shorted turn within the transformer:  this best explains the major power suck that I measure within the transformer itself.

I think I'll have a snowball's chance in you-know-what finding an exact replacement -- any suggestions, though, on what to do for a replacement?  (Or anyone have a Morrow xmtr, working or not, they'd like to part with?)  Or tips regarding winding my own -- do I dare?  ( It's a 1:1 xfrmr, with the primary center-tapped.)

Thanks!

- Jeff, k6jca
http://k6jca.blogspot.com/

[kc2ifr]

Jeff,
I have 2 of those transmitters BUT I dont want to part with them.......sorry......but check out this site. Gary does a great job of rewinding. Wont hurt to check with him.
http://tubes_tubes_tubes.tripod.com/tubestubestubes/id33.html

Bill

[k6jca]

Thanks, Bill!  I've sent an email to Gary requesting a quote.

73,

- Jeff, k6jca

http://k6jca.blogspot.com/

[WU2D]

I would try a TCS mod transformer to test your shorted turn theory.

It may not fit in the Morrow but you can usually find them at festers.

The TCS transformer which originally was for a 1625 modulated by a pair is the correct ratio and power rating for a 50 Watt class transmitter. They are fairly small sealed units with a 6K:6K winding and I have pushed 40W through them. Audio quality fair.

Mike WU2D

[k6jca]

Thanks for the information, Mike.  I'll keep a lookout for one -- it might be kind of fun to roll my own 1625 modulator someday (I think I have a few of those tubes up in the attic).

Regarding the Morrow transformer:  I'm pretty confident it's a shorted turn (my blog describes how I tested for this), and I've sent it out for rewinding and expect it back in a month or so.  We'll see if my theory was correct   (if not, it'll be a costly lesson)!

Best regards,

- Jeff, k6jca

http://k6jca.blogspot.com/

[WZ1M]

Jeff sent me his mod iron to do tests on. I applied 50 volts ac to the secondary and was only able to get 11 volts from center tap to one side of the primary. I was only able to get 20 volts from center tap to the other side of the primary. This, to me, showed shorted turns. After a complete teardown I found the secondary to have 1700 turns while the primary also had 1700 turns with a center tap. With a turns ratio of 1 to 1 I should have 25 volts ac across center tap to each end of the primary. There were many many shorted turns uncovered during tear down.
Thought some of you folks would like to know.
Regards,
Gary

[k6jca]

Thanks, Gary.  I'm glad to know that you've found the problem (and confirmed my suspicions).

[WBear2GCR]

Gary,

Any chance you might share what the general winding arrangement was on this transformer (just because we're talking about it - not out of any special interest in this particular one)?

Maybe a jpeg of the guts?

 

             _-_-bear

Btw, what mod iron that you've redone or opened was the best constructed, and which one(s) were the most interleaved?

Inquiring minds want to know...

[WZ1M]

Bear and to all who mite wont to know. This Morrow transformer had the secondary neasest to the iron core, seperated by 20 mils of paper. The primary was wound over the secondary. The windings on both primary and secondary were not layered wound but were random wound. It WILL NOT be rewound in this fasion. I like to layer wind and seperate each layer with 3 mil mylar. The primary and secondary will be seperated with 10 mil Nomex. 10 mil nomex is good for 1000 volts per mil. Should be enough protection between primary and secondary winding.

[WZ1M]

OOPS, pushed the wrong key. Anyway, the "I" laminations are all on one side with the "E" laminations all on the other side. The air gap between the "I" and "E" laminations was .006. As for what mod iron is constructed the best, hard to say as many brands such as Collins and Johnson used different manufactures for there iron. Must of been a cost and supply thing. I must admit the best piece of mod iron I have rewound was from a Johnson Desk KW. This iron is pretty much the same as the Collins KW-1 iron. I have expereniced mod and audio iron with the laminations not interleaved and also seen a bunch that were interleaved. Guess it depends on saturation level, if that makes sence.
Regards,
Gary

[WA1GFZ]

Interesting primary away form the core so part of the window is air. This should help in controlling saturation.

[flintstone mop]

Would Peter Dahl be of any help to build one to your spec? Or do you like to wind your own?
I wouldn't have the patience to wind and count. It might be like walking and chewing gum at the same time

Fred

[k6jca]

That's an interesting question -- I don't know if Dahl would do a custom rewind.  But I certainly thought about doing it myself, until others pointed me towards Gary's transformer rewinding service: 

http://members.tripod.com/tubes_tubes_tubes/transformerrewindingservice/

And after he informed me that the primary and secondary each had 1700 turns, I'm especially happy that I didn't attempt it myself!

- Jeff, K6JCA

http://k6jca.blogspot.com/