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Power Xfmr secondary voltage

Discussion in 'Shock Brother's DIY Amps' started by dezmoduo, Jan 24, 2021.

  1. dezmoduo

    dezmoduo Tele-Meister

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    I'm building a 2-6V6 PP kit that required a 300V secondary. I used a ClassicTone 40-18130. 120V primary and 3 secondary windings: 39V/3.5ma, 300V/200ma, and 6.3V/3.75ma.

    The 6V6 want to see 406/400 @ pins 3/4 and was reading about 440.

    My question is this. Is there a condition where a 300V spec'd PT, will read 350 with no load. The mains are on but the standby is off. Without tubes installed. Would I be wrong to suspect a mismarked transformer from the supplier?

    Thanks for any input

    Dez
    NYC
     

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  2. NTC

    NTC Tele-Holic

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    I had a similar issue. I think it is 300V when you are drawing 200mA.
     
    King Fan likes this.
  3. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    What @NTC said. In fact, it would be *expected* for any PT to run 10 to 20% higher than nominal with no tubes. Your PT is probably labeled right...
     
    dogmeat and tubedood like this.
  4. dezmoduo

    dezmoduo Tele-Meister

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    Sounds like a consensus on a "No Load" condition. I did run with tubes (and speaker load) but not for long. The 6V6S both red plated quickly. I've ordered the mfg's spec transformer and removed the main board to allow access during the swap. It's a very tight chassis assembly

    Thank you for the insights.

    Dez
    NYC
     
  5. NTC

    NTC Tele-Holic

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    I bought the Hammond 325V at 138ma expecting about 370 to 385 on the plates. I get 420v on 6V6 plates with a 5Y3 and bias at about 68% I get 425V on 6L6 plates at about 70% dissipation with a 5AR4. For the 6L6 version, the amp os drawing about 90ma at idle. The PT voltage is 345 vac.
    So much for expecting 325Vac.
     
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