another Boothill 5F1 question

Discussion in 'Amp Tech Center' started by tahoebob54, Feb 19, 2019.

  1. tahoebob54

    tahoebob54 Tele-Holic

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    A friend of mine is building this amp for me and is having a bit of a problem this is a copy of the email he sent to dave Boothill.

    I am building a 5F1 kit for a friend that bought this kit from you last year. He bought the kit with the Classictone transformers included.

    I had the amp all put together, but had a big issue with an insanely high B+ voltage. Instead of the expected 340 VDC, I am getting around 467 VDC (see picture below for measured voltages).

    I have checked, re-checked, and checked again for any mistakes in my wiring job. I then de-soldered one end of all of the components and verified correct specs. Finally, I disconnected the wiring from the rectifier tube socket to the board, so the power transformer itself is completely isolated, and, the voltage is still sky high.

    At this point, I suspect that the secondary voltage on the power transformer that we got is simply out of specs (too high). I was wondering though if you know of a better or 'special' way to check this. I looked at the spec sheet on classictone.net and by their spec it isn't working correctly.

    Any help you can offer would be greatly appreciated.

    photo.jpg

    [​IMG]



    I have checked, re-checked, and checked again for any mistakes in my wiring job. I then de-soldered one end of all of the components and verified correct specs. Finally, I disconnected the wiring from the rectifier tube socket to the board, so the power transformer itself is completely isolated, and, the voltage is still sky high.

    At this point, I suspect that the secondary voltage on the power transformer that we got is simply out of specs (too high). I was wondering though if you know of a better or 'special' way to check this. I looked at the spec sheet on classictone.net and by their spec it isn't working correctly.

    Any help you can offer would be greatly appreciated. FYI, I copied Bob Peart on this email so ok that you can verify the legitimacy of his purchase.
     
  2. Mr Ridesglide

    Mr Ridesglide Tele-Afflicted Gold Supporter

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    Is that with or without tubes including rectifier?
    Also which Classictone transformer is it?
     
    Last edited: Feb 19, 2019
  3. D'tar

    D'tar Tele-Afflicted

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    With voltages like that I would "guess" your power tube is not conducting for a possible number of reasons.

    To get a better idea of what is happening we need the voltages at each pin of each tube. Ac on the heaters and dc on the rest. Pictures would be helpful also.

    What transformer?

    A lightbulb current limmiter would be a good idea if you have it or can make one.

    https://robrobinette.com/5e3_Modifications.htm#Light_Bulb_Current_Limiter
     
  4. jimgchord

    jimgchord Tele-Holic

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    Most of these kits are going to have the wrong specd transformers. But that's way High, it would seem something else is going on.
     
  5. dan40

    dan40 Tele-Afflicted Silver Supporter

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    If your friend is taking voltage measurements without the tubes installed, the voltages will read high because there is no load on the PT. If the tubes are installed when measuring and the voltage is that high, the 6v6 is likely not conducting as D'tar mentioned.
     
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