g2 tone noise (edited with some test)

    Hello again friends, finally my g2 works!!!
    but i have a hi frecuency noise...if i turn tone all to the left, the noise stops....some idea??

    thanks for your help

    Pedro

    Re: g2 tone noise

    Hi,

    does the noise stop if you pull out the instrument cable?
    Did you ground the cases of the pots?
    Did you deviate from the original layout plan?

    So, no answers but some questions ;D

    Bernd

    Jaichweiß (Andy Pipkin)

    Re: g2 tone noise

    Thanks eBernd for your answers and for your questions :)

    Yes the noise stop when i pull out the guitar..
    i test all grounds and seems to be ok...
    i do the conexions that show the manuals.....
    i have the noise only when i use the tone & up the volume if i put the two in the midle i havent got noise...(in smooth mode) in fat mode the only way to dont have the noise its turn the tone all to the left)

    the noise its a hi tone like the color bars in the video tapes....


    i made same test:

    from v1a pin1 to ground = 169v
    from v1a pin3 to ground = 2v
    from v1b pin6 to ground = 170v
    from v1b pin 8 to ground= 2v
    from v2b pin 5 to ground= 5v
    from v2b pin 6 to ground= 242v
    from r3 to ground = 233v
    blue vs blue = 6v


    i find out that if i low the tone in the guitar the noise stops and i can turn all to the right the tone in the g2 .....
    if i plug only the cable without guitar i have the noise all the time


    i´m sorry for my very bad english i hope you understand what i wanna say....


    Best regards

    Pedro

    Re: g2 tone noise (edited with some test)

    Hi,

    Zitat

    from v2b pin 5 to ground= 5v

    are you shure that this voltage is on pin 5. I expect it on pins 3 and 8.

    Please check the connections to (star)ground (not visual but with a continuity tester or DVM) of...

    input jack (sleeve)
    tone pot mid pin
    tone pot case

    Did you use a shielded cable from th input jack to the circuit?

    Also you can test if the oscillation stops by routing this cable in an other way.

    Please report...

    Bernd

    Jaichweiß (Andy Pipkin)

    Re: g2 tone noise (edited with some test)

    Hi again eBernd:

    yes sorry 5v from pin 8....my mistake.....

    i test grounds with a tester and seem to be ok.....
    some questions :
    what its a shielded cable?.....
    its normal that r1 (input) has ground in the two sides??
    its ok that input and output jacks have ground in all the pins???....


    thanks a lot for your help

    Pedro

    Re: g2 tone noise (edited with some test)

    thanks Kramusha...yes i use a shielded cable to connect the guitar to the jack input..
    i test that when i dont have input jack i have ground in the two sides of r1...but when plug the jack only in one side....

    regards

    Pedro

    Re: g2 tone noise (edited with some test)

    Hi

    Zitat

    what its a shielded cable?.....

    Kramusha gave the answer already. I meant whether you use one inside the amp from the input jack to R2.

    Zitat

    its normal that r1 (input) has ground in the two sides??

    Yes, if no plug is connected to the jack (There is a switch inside the jack wich connects the unused input to ground to avoid hum and noise).

    Zitat

    its ok that input and output jacks have ground in all the pins???....

    Yes, what you measured is the very low resistance of the secondary winding of the output transformer.

    Bernd

    Jaichweiß (Andy Pipkin)

    Re: g2 tone noise (edited with some test)

    Hi,

    I looked at your pics (wich seem to be on a very slow server ;)).

    You should short the shielded cable and connect the shield at the input jack to ground (the other pin on the jack).

    The pot cases are not grounded. Solder wires to both cases (tone and volume) an connect them to ground ( i. e. gnd of input jack).

    The heater wires should be kept near to the chassis and really twisted (you wrapped the red one around the white, that's no twisting).

    Bernd

    Jaichweiß (Andy Pipkin)

    Re: g2 tone noise (edited with some test)

    Hi eBernd:

    i have a lot of improvement!!!!!

    ....in smooth mode i don´t have the whistle at all
    and in fat mode it deppends of the selected pickup....

    Thanks a lot for yor help...i will try to short some connections...
    can i do something else??

    Pedro

    Re: g2 tone noise (edited with some test)

    Yes,

    sometimes the "whistling" depends on the instrument cable: length, quality of shielding, and capacity/length. Standard cable has about 100 pF/m.

    If you have different cables, try them ;)

    If I had a G2 I would take two SPST switches. So you can switch FAT and SMOOTH separately. OK, you would need another 6 mm hole in the chassis.

    Bernd

    edit:

    I found another thing you can try:

    The blue wire from the OT ist quite near to the input section. Try and route it the same way as the brown wire - away from the input copmonents.

    Jaichweiß (Andy Pipkin)

    Re: g2 tone noise (edited with some test)

    uhmm interesting...its better has smooth & fat separately?.
    can you explain how to made it? .
    im enjoyning a lot with this amp! ;)

    Best Regards

    Pedro

    Re: g2 tone noise (edited with some test)

    Dear friend:

    i short some wires, routed the blue wire like the brown, and test with other guitar cable and now i don´t have whistle at all.. ;D ;D ;
    thank you very much for your help....

    its time to start to make the cabinet!!!!!

    Best Regards

    Pedro

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