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Title: SX-28 Power Transformer Post by: WA8RVD 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 Title: Re: SX-28 Power Transformer Post by: KM1H 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 Title: Re: SX-28 Power Transformer Post by: The Slab Bacon 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.
Title: Re: SX-28 Power Transformer Post by: WA8RVD 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 Title: Re: SX-28 Power Transformer Post by: WA8RVD 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 Title: Re: SX-28 Power Transformer Post by: KB2WIG 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 Title: Re: SX-28 Power Transformer Post by: ke7trp 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 Title: Re: SX-28 Power Transformer Post by: n1ps 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 Title: Re: SX-28 Power Transformer Post by: WA8RVD 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.
Title: Re: SX-28 Power Transformer Post by: WA8RVD on April 18, 2012, 05:35:10 PM UPDATE: AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
The transformer works well and fit well! This SX-28 lives again! |