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Re: AppleColor RGB all-red display

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From dog_cow@macgui.com (D Finnigan)
Newsgroups comp.sys.apple2
Subject Re: AppleColor RGB all-red display
Date Tue, 18 Oct 2011 17:41:43 +0000 (UTC)
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Michael J. Mahon wrote:
> D Finnigan <dog_cow@macgui.com> wrote:
>> The story continues:
>> 
>> Yes, it was a bad transistor for the red channel. It tested differently
>> compared to the blue and green transistors. Using better light, I could
>> also
>> see scorch marks on the PCB from where I'd apparently made a short
>> circuit
>> the other day.
>> 
>> Next step now is to find out what kind of transistor it is, and get a
>> replacement part.
> 
> Glad you found it. 
> 
> I'd guess a high voltage (50-70v) medium beta NPN. After replacement you
> may need to adjust the red brightness ("screen") and contrast ("gain") to
> get the colors right again. 
> 

I just researched the transistor number, and it appears to be a standard
part: C2688.

<http://search.digikey.com/us/en/cat/discrete-semiconductor-products/transistors-bjt-single/1376376?k=c2688>

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Thread

AppleColor RGB all-red display dog_cow@macgui.com (D Finnigan) - 2011-10-15 17:38 +0000
  Re: AppleColor RGB all-red display dog_cow@macgui.com (D Finnigan) - 2011-10-15 17:41 +0000
    Re: AppleColor RGB all-red display Grent <grent3@gmail.com> - 2011-10-15 17:33 -0700
      Re: AppleColor RGB all-red display dog_cow@macgui.com (D Finnigan) - 2011-10-17 20:47 +0000
        Re: AppleColor RGB all-red display dog_cow@macgui.com (D Finnigan) - 2011-10-18 14:19 +0000
          Re: AppleColor RGB all-red display Michael J. Mahon <mjmahon@aol.com> - 2011-10-18 12:05 -0500
            Re: AppleColor RGB all-red display dog_cow@macgui.com (D Finnigan) - 2011-10-18 17:41 +0000
              Re: AppleColor RGB all-red display Grent <grent3@gmail.com> - 2011-10-18 23:27 -0700
              Re: AppleColor RGB all-red display Alex Freed <alex_news@alexfreed.com> - 2011-10-19 02:10 -0700
                Re: AppleColor RGB all-red display Michael J. Mahon <mjmahon@aol.com> - 2011-10-19 16:08 -0500
                Re: AppleColor RGB all-red display Kevin Dady <kevin@hackaday.com> - 2011-10-19 18:16 -0700
                Re: AppleColor RGB all-red display Alex Freed <alex_news@alexfreed.com> - 2011-10-20 01:25 -0700

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