NPN transistor problem

Discussion in 'General Electronics Chat' started by caseysmydog, Feb 23, 2012.

  1. caseysmydog

    Thread Starter New Member

    Feb 23, 2012
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    Please don't laugh, but a transistor in circuit is measured at its legs using AC scale and not DC. Many thanks-- this is important. (The schematic says like 7.4 volts)

    Sorry, did not post a title so re-posting.
    Do you measure an NPN transistor, in circuit, using AC or DC volts...schematic says on one leg (7.4 V) Many thanks....

    The schematic is located at http://freepdfhosting.com/a2a50fc93b.pdf
    and is Q7 & Q8. Would Q9 be AC or DC?
     
    Last edited by a moderator: Feb 24, 2012
  2. #12

    Expert

    Nov 30, 2010
    16,354
    6,852
    Welcome to AAC.

    Now about that schematic...if I could see it I might know what you are talking about. Can you post the schematic here by using the "Go Advanced" button? The best format is .png

    You can make a drawing with the Paint program in Windows computers. You can make a pencil drawing and scan it, then upload it. There are several ways to get a drawing to appear with your question.

    Next item, what is your question?
     
  3. #12

    Expert

    Nov 30, 2010
    16,354
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    It's usually measured as DC but it depends on what the transistor is doing.

    This answer has become seperated from its thread. I have reported it to the moderators so they can find its home and put it where it belongs.
     
    Last edited: Feb 24, 2012
  4. #12

    Expert

    Nov 30, 2010
    16,354
    6,852
    Turn the volume control to zero and measure them as DC.
     
  5. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    It also helps if you choose a subject line that makes at least some sense. Casey is meaningless other than maybe to you.
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    Well, it didn't go exactly as planned, but I merged all the posts into one post.

    Casey, Welcome to AAC.

    Instead of splattering the forum with a bunch of posts all about the same project, it is better to focus on one thread. It is how it is done here.

    You will find you can attach your images here in the form of attachments <wince>.

    To attach a document or picture to a post

    Click "Go Advanced" at the bottom of your post,

    One of several options will pop up,

    Click "Manage Attachments" much further at the bottom of your post,

    To upload a file from your computer click "Browse", then select the file.

    Schematics should be .gif or .png format, pictures should be .jpg. .jpg formats will fuzz out schematics, and should not be used for that purpose.
     
  7. Audioguru

    New Member

    Dec 20, 2007
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    The RCA radio is more than 50 years old and should be buried.
    The voltages shown on the schematic are DC voltages when the radio is not playing. The voltages of Q9 are shown to be B= +7.4V, E= +6.8V and C= +72V.
     
  8. Audioguru

    New Member

    Dec 20, 2007
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    I already answered the other thread about this same very old RCA radio.
     
  9. Wendy

    Moderator

    Mar 24, 2008
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    Looks like I did it again. Some threads were left behind from the last merge, so I did it again.
     
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