Need help with Thordarson xformer specs

Discussion in 'Shock Brother's DIY Amps' started by Salty_critters, Jun 5, 2020.

  1. Salty_critters

    Salty_critters TDPRI Member

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    I'm building a monoblock stereo using the "30-watt hi-fi amp" in the back of the RCA tube manual. I was fortunate enough to locate the original Thordarson power transformer that is listed on the RCA amp's parts list. I'm trying to match it with a similar model Thordarson transformer (or an identical one, if i should be so lucky), but I am coming up dry on every search for specs on these transformers.
    I have found a two power transformers that could work, T-52285 and T-41562, but all the documentation I have searched through makes no mention of Thordarson xfrmrs using a T-XXXXX serial number. They are either T-XXXX or XXRXX, or something like that.
    Can anyone help me in gathering specs for a T-52285 or T-41562 Thordarson transformer? Or Thordarson transformer with a T-XXXXX serial?? This is driving me nuts! :(
     
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  2. Wally

    Wally Telefied Ad Free Member

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    What is the model number on the transformer you have there??? There are several T code Thordarson transformers on eBay, and wo knows...someone where might have one sitting around????
     
  3. Wally

    Wally Telefied Ad Free Member

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    Edit duplication...
     
  4. Salty_critters

    Salty_critters TDPRI Member

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    I have a T70R62, otherwise known as the T22R33. 375-0-375V @ 160mA, + filament windings.
    Thats the PTx that is listed on the 30W amp's part list. I think I found a identical model on ebay, the only difference being that it is the lay-down version. The T22R33 is mounted upright.
    Ever used lay-down style transformers WITHOUT punching a giant square hole in your chassis?
     
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  5. tubegeek

    tubegeek Tele-Afflicted

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    Do you have a source for some 7199s? Or a plan for a substitution? Those are very hard to find at any reasonable price, a lot of popular amps used them and they've gotten tricky to find.
     
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  6. tubegeek

    tubegeek Tele-Afflicted

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    Easy to go the other way - take the feet off the end bells and cut the big hole. (So long as the leads don't come out of both sides.)
     
  7. Wally

    Wally Telefied Ad Free Member

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    The 6AN8 is a sub for the 7199 with a wiring change on the socket. I don’t hold much hope, Salt_critters, but I will take a look around at my odds and ends for a tranny. 7199s??. I am holding what I have which is no more than two. I have two amps that use that tube, and I like those two amps. I do have some 6AN8s....quantity unknown.
     
  8. tubegeek

    tubegeek Tele-Afflicted

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    If you do end up with a pair of those 6AN8s that are excess to your needs, let's make a deal?

    I would love to hear this Dynaco st70 someday - and I surely can rewire a socket. 7199s are the only thing missing.
     
  9. Wally

    Wally Telefied Ad Free Member

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    Let me check, tubegeek. The 6AN8s are not as hard to find.
     
  10. Wally

    Wally Telefied Ad Free Member

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    Tube geek, I am walking in my sleep here this afternoon. I started looking and found more than I bargained for, and I would have to delve into things a bit to try to understand things. You might do some research. I have some 6AN8s, I have some 6U8As. And...in doing some research, I typed in 6AU8 at the Tube Data Sheet Locator.....that is a triode/Pentode tube as well.....maybe not ideal but....
    I’ll keep looking to see the extent of what I have. I need to get these tubes into the tube boxes I have so that they are more ‘available’. I am amazed at all of the tubes that have come my way.
     
  11. Ten Over

    Ten Over Tele-Holic

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    AES has a little converter socket for 7199 to 6GH8A and the 6GH8A is dirt cheap.
     
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  12. Wally

    Wally Telefied Ad Free Member

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    Yeah..6GH8A, ..6LH86????.... I get I need to get these things organized and sold, because they have been telling me for 69 years that life is short, right??? Eeeehaw.....
    I get overwhelmed when I start going through my tubes. I had forgotten about some of these things I got in a small military stash. I have some 6DJ8/6922 tubes that make a 7199 seem cheap.....they are dual triodes so I am just talking about expense now. Some of these tubes are worth from $300-1,000 a pair from a reputable distributor!
     
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  13. Wally

    Wally Telefied Ad Free Member

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    As for why the 7199s are more costly, as I understand it they were designed from the start as a high quality audio amplification tube. Some of these other subs were designed for others purposes. There are differences.
     
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  14. tubegeek

    tubegeek Tele-Afflicted

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    I believe you are right. Also - from the demand side, there were a LOT of ST70's sold/built and many are still kicking.
     
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  15. Wally

    Wally Telefied Ad Free Member

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    Lots of guitar oriented amps that used the 7199 I; addition to those Dynaco designs, and I would think that the 7199 was not made in the numbers that say 12AX7s were made. The triode/pentode structure might have been inherently more costly to build, as well.
    Anyway.....here is a guitar amp with a 7199 in it...pentode preamp gain and triode phase inverter......fantastic Alamo.
    It was dead when it came to me. There is no schematic known for it out here in the world. After getting it going and playing through, I had to draw the schematic out of Curiosity. Very interesting treble control that acts as a mid boost as you turn it counterclockwise. it is some sort of Baxandall tone circuit, I think....I wish I knew more.
    D52C156E-E8FA-4763-B193-3A9E98C04639.jpeg
    F6B3BB6C-4BC2-4D44-BEAF-111DBFBAD666.jpeg
     
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  16. Salty_critters

    Salty_critters TDPRI Member

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    Little late to the discussion, but someone above mentioned the 6GH8 tube as a sub for the 7199; that was my first thought! I've read on the web that 6GH8A will work best out of the 6GH8/6U8/6LN8/ etc family, when subbing for a 7199. I have played around with 6LB8's, and love 'em, but BL8's have much lower voltage limitations than a 7199.

    I was fortunate enough to find two 7199's, fairly cheap, on everyone's favorite auction site.
     
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  17. David Barnett

    David Barnett Doctor of Teleocity

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    A 1950s power transformer will be wound with a primary that expects 110-115V AC, and will give high voltages with the 120-125V+ that we get today.

    I'd suggest looking through Hammond's selection of transformers to find a model that meets spec, and buy two of them.
     
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  18. Wally

    Wally Telefied Ad Free Member

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    yeah, the problem with any of the ‘subs’ for the 7199 is that none of them were designed for the purpose for which the 7199 was designed..which was high fidelity audio amplification. The others were designed for television applications...non-audio....deflectors, oscillators. They ‘work’...but they are not designed for the purpose.
     
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