Groups > sci.electronics.design > #452915

Re: Amplifier transistor substitution.

From	Cursitor Doom <curd@notformail.com>
Newsgroups	sci.electronics.design, sci.electronics.repair
Subject	Re: Amplifier transistor substitution.
Date	2017-03-21 18:18 +0000
Organization	A noiseless patient Spider
Message-ID	<oarqpg$b5u$1@dont-email.me> (permalink)
References	<ej4csuFe5h4U1@mid.individual.net> <ej6jjmFrr5fU1@mid.individual.net> <oam3me$oce$6@dont-email.me> <dbKdneGOEI5t2kzFnZ2dnUU7-afNnZ2d@giganews.com>

Cross-posted to 2 groups.

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On Tue, 21 Mar 2017 08:34:08 -0700, John Robertson wrote:

> You may be able to find your BF472s sourced from India:
> 
> http://www.diyaudio.com/forums/solid-state/269984-bf471-472-good-
replacement-2sa1381-2sc3503.html
> 
> I did a search and no BF numbers showed up, however they did manufacture
> the device recently according to the referenced PDF. You may have luck
> tracing the part through CDLI's distribution network. It never hurts to
> ask!

Is Indian stuff kosher? Like others here I've had big problems with fake 
semis from the far east; voltage regs in particular.

> 
> I would also check T710 (BF458) and T707 (BF199) as well though before
> ordering anything. A simple gain test should suffice. Try to find a
> reliable source for these transistors, there are a lot of Chinese (etc.)
> fakes out there!

Oh yes, see above!

> Have you upgraded the electrolytic capacitors in your scope? They are
> most likely well past their Best-Before date!

They were *all* totally fine! I mean I'm sure they're not as they were 
when new, but none of us are. ;-) The fault with that scope (if it's the 
one I'm thinking of) turned out to be a diode in the SMPS section that 
someone had subbed with an inferior part. It needed a fast recovery diode 
and someone had stuck in the first spare diode the could find I'd 
imagine. It would have worked fine at 50Hz but this was 20kHz. One of the 
guys who posts here spotted it from a photo I posted!

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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