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    KNIGHT KA 40 REBUILD

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    rfbro

    Posts : 26
    Join date : 2014-12-28
    Age : 61
    Location : Vancouver WA

    KNIGHT KA 40 REBUILD

    Post by rfbro on Thu Jan 14, 2016 10:07 pm

    what are the function of the 2 resistors in the middle of these tube sockets? If one is bad what symptoms could i expect..TKS Bob B


    Last edited by rfbro on Fri Jan 15, 2016 12:02 am; edited 1 time in total

    rfbro

    Posts : 26
    Join date : 2014-12-28
    Age : 61
    Location : Vancouver WA

    Re: KNIGHT KA 40 REBUILD

    Post by rfbro on Thu Jan 14, 2016 11:23 pm

    [quote="rfbro"]what are the function of the 2 resistors in the middle of these tube sockets? If one is bad what symptoms could i expect..TKS Bob B


    peterh

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    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: KNIGHT KA 40 REBUILD

    Post by peterh on Fri Jan 15, 2016 2:34 am

    look at the schematics !

    rfbro

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    Re: KNIGHT KA 40 REBUILD

    Post by rfbro on Fri Jan 15, 2016 9:13 am

    peterh wrote:look at the schematics !
    I must as soon by the answer that you have given you haven't got the foggiest idea but thank you for the effort

    Elrick

    Posts : 71
    Join date : 2012-09-02
    Location : Bellingham WA

    Re: KNIGHT KA 40 REBUILD

    Post by Elrick on Fri Jan 15, 2016 9:22 am

    Not enough information. peterh is correct, you either need to either draw it out or provide the schematic. The schematic is probably out there somewhere.

    arledgsc

    Posts : 340
    Join date : 2012-11-30
    Location : SF Bay CA

    Re: KNIGHT KA 40 REBUILD

    Post by arledgsc on Fri Jan 15, 2016 11:21 am

    Appears to be a cathode follower type circuit where the first stage voltage amplifier feeds the grid of the second stage cathode follower. The resistor at the tube socket (pins 2 and 7) is the plate resistor of the first stage.

    A cathode follower is near unity gain but lowers output impedance versus a plate driven circuit. In guitar amps a cathode follower drives the tone control stack to minimize interaction of the driving circuit.

    rfbro

    Posts : 26
    Join date : 2014-12-28
    Age : 61
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    Re: KNIGHT KA 40 REBUILD

    Post by rfbro on Fri Jan 15, 2016 11:35 am

    arledgsc wrote:Appears to be a cathode follower type circuit where the first stage voltage amplifier feeds the grid of the second stage cathode follower.   The resistor at the tube socket (pins 2 and 7) is the plate resistor of the first stage.  

    A cathode follower is near unity gain but lowers output impedance versus a plate driven circuit.  In guitar amps a cathode follower drives the tone control stack to minimize interaction of the driving circuit.
    thank you if the resistor is bad would this cause no sound from that ccannel

    arledgsc

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    Re: KNIGHT KA 40 REBUILD

    Post by arledgsc on Sun Jan 17, 2016 1:21 pm

    If you can find a schematic would help tremendously. But in generalities an open plate resistor would mean no signal for the next stage.

    1M ohm plate resistor, if it is indeed a plate resistor, is quite a large value. Could be some form of negative feedback resistor as well. A schematic would tell us for sure.

    An ohmmeter will tell a lot about the health of the resistors if in doubt. Power off and filter caps discharged first.





    rfbro

    Posts : 26
    Join date : 2014-12-28
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    Re: KNIGHT KA 40 REBUILD

    Post by rfbro on Sun Jan 17, 2016 10:47 pm

    arledgsc wrote:If you can find a schematic would help tremendously.  But in generalities an open plate resistor would mean no signal for the next stage.  

    1M ohm plate resistor, if it is indeed a plate resistor, is quite a large value.   Could be some form of negative feedback resistor as well.  A schematic would tell us for sure.

    An ohmmeter will tell a lot about the health of the resistors if in doubt.  Power off and filter caps discharged first.




    http://i1297.photobucket.com/albums/ag25/masdaspeed3/SCAN0027_zpsbj4cw705.jpg


    Last edited by rfbro on Mon Jan 18, 2016 10:24 pm; edited 1 time in total

    MontanaWay

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    Re: KNIGHT KA 40 REBUILD

    Post by MontanaWay on Mon Jan 18, 2016 12:17 am

    it really does not help if you post links to diagrams where one needs to log in, in order to see them.
    Copy that diagram and post it on here.

    arledgsc

    Posts : 340
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    Location : SF Bay CA

    Re: KNIGHT KA 40 REBUILD

    Post by arledgsc on Mon Jan 18, 2016 10:59 am

    Appears to be the 3B and 4B stages.   They are just voltage amplifiers driving the 7189 phase inverters.

    The schematic diagram is small plus it is upside down.  When you zoom in you lose detail.  But here is the diagram.pdf corrected as much as I can.
    Knight KA-40 Schematic

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