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Re: Amplifier transistor substitution.

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On 18/03/2017 8:27 PM, Sylvia Else wrote:
> The smoke escaped from my old oscilloscope today. I've determined that
> it came out of R740, to the bottom right of the circuit diagram.
>
> https://www.dropbox.com/s/9053dnyr0izv88r/XAMP.PDF?dl=0
>
> This is because T711 has shorted out.
>
> Not very surprisingly I cannot source a replacement BF472, so I need to
> find a substitute.
>
> This is the final X-axis amplifier, so we're not talking high
> frequencies. Is it likely to be sensitive to the particular transistor
> characteristics?
>
> Sylvia.

Hmm....

They may have supplied a circuit diagram and board layouts in the user 
manual, but this thing is clearly not designed to be repaired. There are 
multiple wires soldered directly to the boards, including some of those 
from the power transformer, and to the side of the board that's not 
readily accessible until after they're been desoldered. How did they 
assemble this thing? With some kind of right-angled soldering iron?

Sylvia.

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Thread

Amplifier transistor substitution. Sylvia Else <sylvia@not.at.this.address> - 2017-03-18 20:27 +1100
  Re: Amplifier transistor substitution. "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> - 2017-03-18 10:41 +0000
    Re: Amplifier transistor substitution. Cursitor Doom <curd@notformail.com> - 2017-03-18 11:13 +0000
    Re: Amplifier transistor substitution. bitrex <bitrex@de.lete.earthlink.net> - 2017-03-18 18:15 -0400
      Re: Amplifier transistor substitution. Sylvia Else <sylvia@not.at.this.address> - 2017-03-19 12:44 +1100
        Re: Amplifier transistor substitution. Winfield Hill <hill@rowland.harvard.edu> - 2017-03-18 19:03 -0700
          Re: Amplifier transistor substitution. Sylvia Else <sylvia@not.at.this.address> - 2017-03-19 13:14 +1100
          Re: Amplifier transistor substitution. Cursitor Doom <curd@notformail.com> - 2017-03-19 14:11 +0000
            Re: Amplifier transistor substitution. Winfield Hill <hill@rowland.harvard.edu> - 2017-03-20 06:20 -0700
              Re: Amplifier transistor substitution. Cursitor Doom <curd@notformail.com> - 2017-03-20 23:26 +0000
  Re: Amplifier transistor substitution. Phil Allison <pallison49@gmail.com> - 2017-03-18 04:08 -0700
    Re: Amplifier transistor substitution. Sylvia Else <sylvia@not.at.this.address> - 2017-03-18 22:42 +1100
      Re: Amplifier transistor substitution. "Benderthe.evilrobot" <Benderthe.evilrobot@virginmedia.com> - 2017-03-18 22:01 +0000
  Re: Amplifier transistor substitution. Sylvia Else <sylvia@not.at.this.address> - 2017-03-19 16:34 +1100
    Re: Amplifier transistor substitution. Cursitor Doom <curd@notformail.com> - 2017-03-19 14:13 +0000
      Re: Amplifier transistor substitution. John Robertson <spam@flippers.com> - 2017-03-21 08:34 -0700
        Re: Amplifier transistor substitution. Cursitor Doom <curd@notformail.com> - 2017-03-21 18:18 +0000
  Re: Amplifier transistor substitution. Sylvia Else <sylvia@not.at.this.address> - 2017-03-20 13:28 +1100
    Re: Amplifier transistor substitution. Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2017-03-20 10:59 +0200
      Re: Amplifier transistor substitution. Sylvia Else <sylvia@not.at.this.address> - 2017-03-21 10:57 +1100
  Re: Amplifier transistor substitution - fixed. Sylvia Else <sylvia@not.at.this.address> - 2017-03-22 19:33 +1100

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