Need A Modulation Transformer For That 500 Watt Final?

Discussion in 'Amplitude Modulation' started by W2VW, Jun 4, 2020.

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  1. W2VW

    W2VW XML Subscriber QRZ Page

    KD2ACO, W2BTK, AD5HR and 1 other person like this.
  2. AD5HR

    AD5HR Ham Member QRZ Page

    W2VW likes this.
  3. K5UJ

    K5UJ Ham Member QRZ Page

    For some reason, QRZ is set up so that in order to see a for sale post, you have to be logged in. I cannot fathom the need for being logged in, only to see a for sale post. I don't need to be logged in to see stuff posted here so what's the difference other than FUD regarding scammers. This is yet another reason why the for sale forum is practically worthless to me. swap.qth.com is way better. Maybe most users are set up to automatically log in, or stay logged in all the time. I try to minimize being logged in and do so only to post a comment which makes sense to me. Logging in for every single thing is a nuisance.
     
  4. N2DTS

    N2DTS Ham Member QRZ Page

  5. W2VW

    W2VW XML Subscriber QRZ Page

    Was spoken for, now for sale again : )
     
  6. W2VW

    W2VW XML Subscriber QRZ Page

    Hence the line mentioning backing the xfmr just enough for the pitch to reflow. I used the old barbecue which was slated for replacement. I also cooked several other transformers using the same method. Every one has been fine. This is the last one left from that batch.

    Personally I always find a way to heat any older iron after losing a few old transformers due to haste.

    The worst was my "someday" plate transformer which was loaned to a contester neighbor in the middle of the night during a winter 1986 contest.

    That transformer worked extremely well for a few hours.

    After that failure I loaned the guy a pair of Thordarson CHT 105 lb plate transformers which I personally hooked up in parallel for full wave centertap rectification.

    I instructed him not to try full wave bridge because the center tap was not rated for that hookup.

    You can guess the contents of the phone call that happened a few hours later.

    I still remember heaving those up on the back of Gus the scrap guys truck and watched them head down the road to become a new Toyota.

    Anyone using older iron who might not be familiar with the proper use of spark gaps should read K4KYV's writings.
     
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  7. K5UJ

    K5UJ Ham Member QRZ Page

    What do you mean by haste? You mean not giving it time to dry out?
    I'm not surprised. I have a CHT T47000. Can't find data for it on-line but I think it's about 200 lbs. I'd never allow a non-technical ham use it.
    PowerSupplyParts_3KV_painted - 2.jpeg
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    Last edited: Jun 6, 2020
  8. W2VW

    W2VW XML Subscriber QRZ Page

    Yes, drying it out one way or another. As usual I have a typo too. Not backing, baking!

    English is my second language.

    Your transformer is similar to the pair I mentioned only much larger. Do you have a picture of the output taps Rob?

    I found another several Thor plate xfmrs in the basement of Atkinson and Smith Electronics in Eatontown, N.J. when Smitty was about to retire. They were packed in crates along with Wilcox autotransformer type modulation iron and sets of Wilcox swinging and smoothing chokes. IIRC the crates had mid to late 1940s dates.

    One is in service on my Johnson 500 or Johnson Kilowatt. They currently share the same supply/modulator. Also makes a nice test set.

    The best old iron for a 5.5 or 6kv ps is the later BC-610 or T-368 types. They are oil filled and the centertap will not zorchover when used with a full wave bridge. I have been using them for years in pairs. Have NOT tried this without a choke input however.

    Modern xfmrs and voltage doublers and even large toroids with a bunch of rectified secondaries in series perform fine.

    OM Power uses toroids with stacked rectified multiple secondary windings to reach the high 2KV range. This is possible because of the much better insulation than ancient iron. I'm not sure why OM didn't just place the individual windings in series and use one rectifier.

    Even the more common Antek toroids which have been used by several AMers as modulation transformers do not self destruct at 3kv.
     
  9. K5UJ

    K5UJ Ham Member QRZ Page

    PowerSupplyParts_3KV_painted - 3.jpeg
    h.v. side
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    Primary
    What is your native language?
     
  10. W2VW

    W2VW XML Subscriber QRZ Page

    Thanks. That looks like full wave centertap only but that's a guess.

    My native language is English.

    I had to learn much of it twice.
     

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