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Determine 9v/12v of QDX?

 

I have an old QDX I started building years ago (Rev 3) and I wound the PA transformer...and promptly forgot if I wound it for 12v or 9v.
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I'm looking to work on finishing it now and reading the conventional winding docs is hurting my head, no idea how I managed to do it the first time. Is there an easy way to spot and tell if it's wired for 9v before I plug it up to a battery and fry it? Can I tell just off the number of turns on each side or do I have to do something else?
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Apologies for the semi-simple question: brand new to kit builds and trying to get the old stuff I started and never finished on the air XD
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73,
CJ WW0CJ
 

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Just a WAG here, and not a technical one - why not power it up with 9v and use PuTTY and a dummy load to see how much power it generates. Seems like if it was wound for 9v you should get full 4-5 watts. If wound for 12v, much less output.

Jim

On Mar 12, 2025, at 2:43?PM, CJ - WW0CJ via groups.io <cjtheham@...> wrote:

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I have an old QDX I started building years ago (Rev 3) and I wound the PA transformer...and promptly forgot if I wound it for 12v or 9v.
?
I'm looking to work on finishing it now and reading the conventional winding docs is hurting my head, no idea how I managed to do it the first time. Is there an easy way to spot and tell if it's wired for 9v before I plug it up to a battery and fry it? Can I tell just off the number of turns on each side or do I have to do something else?
?
Apologies for the semi-simple question: brand new to kit builds and trying to get the old stuff I started and never finished on the air XD
?
73,
CJ WW0CJ

--
Jim / K7TXA
Eagle, ID

SKCC 10447T
BUG 301
 

Guess I could do that...didn't process that it would work at 9v with the 12v winding just be low output. I'll have to figure out a way to hook it to a bench supply because I don't have another 9v source handy but that's much easier in a way XD
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Thanks for the suggestion Jim!
 

I bought a used QMX, and the seller forgot if it was a 9V or 12V, he had built so many and lost track.? I opened it, took a picture of T501 from the side with my phone, and enlarged the picture.? Made it easy to count the number of turns and verify it was a 9V.??
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Then I hooked it up to a 9V source and got 4-5 Watts out at about 1 Amp into a dummy load, which confirmed 9V behavior.
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73
Mike N9OHW
 

And the current it pulls, as mentioned. About 1A @ 9V for a 9V build. Would be less, like 0.7-0.75A on a 12V build, I believe.
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-Nate
N8BTR

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