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Author Topic: SX-28 Power Transformer  (Read 7045 times)
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WA8RVD
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« on: April 04, 2012, 10:47:46 AM »

Hello All,
I have a bad power transformer in my SX-28.  The manual says it should have a 580 volt center tapped @ 185 ma secondary. I have found Hammond transformers - one with a 550 v @ 230 ma secondary and one with a 600 v @ 230 ma secondary.  Which would be the better choice?

Mike
WA8RVD
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KM1H
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« Reply #1 on: April 04, 2012, 12:23:54 PM »

The lower one as long as it fits. You dont need a high B+ in that radio anyway as there is already excessive gain and I doubt you will be running the audio at full bore.

Plus the higher line voltage today will likely make up for the difference.

Carl
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The Slab Bacon
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« Reply #2 on: April 04, 2012, 12:29:05 PM »

Make sure that the 6.3V filament winding has enough BAs to carry all of the tubes. That radio has a pretty serious filament load.
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"No is not an answer and failure is not an option!"
WA8RVD
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« Reply #3 on: April 04, 2012, 12:31:52 PM »

Thanks, Carl
That's what I was thinking but I already made one big mistake yesterday and have lost confidence in my own judgement.  Glad to hear from you - I greatly value your contributions to the forum.
Thanks,
Mike
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WA8RVD
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« Reply #4 on: April 04, 2012, 12:37:37 PM »

It is a Hammond;
270HX 115v pri,  550V C.T. @ 230 ma. 5V C.T. @ 3A 6.3V C.T. @ 6A
the SX-28 manual part description is: 580v C.T. @ 185 ma.  5v @ 3A.  6.3 @ 5.5A
So I should be OK and it should fit.

Thanks all
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KB2WIG
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« Reply #5 on: April 04, 2012, 01:54:51 PM »

" That radio has a pretty serious filament load."

Ya can always ss the power supply and save 3 amps on the 5z3.  And series up the 5v winding to drop the primary voltage a bit.


klc
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ke7trp
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« Reply #6 on: April 04, 2012, 04:14:25 PM »

That sounds like a great transformer for the 28.  While you are at it, Pick up the hammond Audio transformer. It makes one hell of a difference in sound quality.  Its so hi fi you think where listening to an FM station on a Good stereo system.

C
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n1ps
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« Reply #7 on: April 04, 2012, 08:01:21 PM »

There are some people who rewind xformers.  This is another option.  I think Gary still offers this:  xfrmrs@roadrunner.com

Peter
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WA8RVD
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« Reply #8 on: April 04, 2012, 08:26:41 PM »

If this were the original xfmr I would have it rewound but it was also a replacement.  The new one is less money than a rewind.
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WA8RVD
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« Reply #9 on: April 18, 2012, 05:35:10 PM »

UPDATE:
The transformer works well and fit well!
This SX-28 lives again!
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