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b&k FUNCTION GENERATOR

Discussion in 'Troubleshooting and Repair' started by chucksue, Jan 31, 2013.

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  1. chucksue

    chucksue

    7
    0
    Jan 31, 2013
    I need help troubleshooting a b&k 3011b generator.The readout shows frequency change but there is no output at the b and c connector.There are two transistors just before the output and they are heat sinked and they are very hot.
     
  2. shrtrnd

    shrtrnd

    3,808
    511
    Jan 15, 2010
    Sounds like you've got an output problem, but the generator itself is still working.
    I'd find a manual (schematic) for it if I could.
    I think you mean a 'BNC' connector for the output.
    Your transistors are heat sinked, so they're supposed to get hot. They may be bad, but
    something in front of them made them get that hot if you've got no output.
    A schematic should help you a lot in isolating the problem.
     
  3. chucksue

    chucksue

    7
    0
    Jan 31, 2013
    3011b

    I found a schematic on line and bought it.The two transistors that get hot are the last ones before the output.In the circuit with the transistors are two electrolytic caps..They may be bad I haven't checked them yet.The transistors are set up like a push pull or a balanced circuit.
     
  4. davenn

    davenn Moderator

    13,798
    1,939
    Sep 5, 2009
    can you scan around that section of the circuit and post it ?

    it may be easier to help you if we can see how its layed out

    Dave
     
  5. chucksue

    chucksue

    7
    0
    Jan 31, 2013
    3011b

    I'll scan it and try to post it soon
     
  6. chucksue

    chucksue

    7
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    Jan 31, 2013
    3011b schematic
    Dave how do you post the schematic?I scanned it and have it in my doc's.I clicked on insert a image if that is where it is done.It asked for a htpl or something like that. ???????????
     
  7. chucksue

    chucksue

    7
    0
    Jan 31, 2013
    3011b

    Here is the b and k schematic.

    [​IMG]

    Please let me know if you are not able to view it.
     

    Attached Files:

    Last edited by a moderator: Feb 5, 2013
  8. chucksue

    chucksue

    7
    0
    Jan 31, 2013
    3011B

    The base to emitter voltages on the Q502 Q501 Q504 Q505 transistors all are around .7 volts.The Q503 has 2.84 volts base to emitter.
    I replaced the 2n2905 transistor and it got hot also.I cut the base lead on this transistor and it didn't get hot.The base must be over biased.The signal atVR502 has all wave forms on it when I select the sine,square and saw tooth wave form.I do not see any out put on the collector of Q501.
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,482
    2,830
    Jan 21, 2010
    I'd check F501 (just in case)

    And 2.84 V between base and emitter on Q503 seems very wrong. Just check again that you haven't measured base and collector. (It should be the same voltage as is across R502)

    A failed Q503 *might* be affecting the signal at the collector of Q501. Remove Q503 (at least the base connection) and see if the signal reappears (at the collector of Q501).
     
  10. chucksue

    chucksue

    7
    0
    Jan 31, 2013
    3011 B

    I had to remove the Q503.They have all the transistors soldered down close to the board.I still do not have any signal at the collector but a lot of static.I will order transistors to replace the 503.We will see what happens then.The base to emitter voltage I checked and it was high.Looking at the transistor the base and emitter should be the outside leads.I down loaded the data sheets to be sure.
     
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