1. Win a Broadcaster or one of 3 Teles! The annual Supporting Member Giveaway is on. To enter Click Here. To see all the prizes and full details Click Here. To view the thread about the giveaway Click Here.

6g15 help

Discussion in 'Shock Brother's DIY Amps' started by mooncat, Aug 23, 2020.

  1. mooncat

    mooncat TDPRI Member

    Posts:
    6
    Joined:
    Oct 7, 2019
    Location:
    uk
    Hi all
    Have just finnished building a 6g15 and i've got a voltage reading of 62volts on pin 7 on the 12ax7 and it should be 120volts, all the other voltages are within tolerance.
    I have checked an double checked all of the components and connections and they are correct.
    If i connect another 2.2m resistor in parallel with the NFB voltage divider 2.2m resistor the voltage comes up to 103 volts.
    Should i change the 2.2m voltage divider resistor to 1.1m?
    Or am i missing somthing?
     
  2. Tom Kamphuys

    Tom Kamphuys Tele-Holic

    Age:
    41
    Posts:
    724
    Joined:
    Sep 18, 2018
    Location:
    The Netherlands
    I guess you are talking about this:

    Screenshot_20200823-203753.png

    Looks like a simple voltage divider made up of the two 2.2M resistors. Is the voltage at the top of them 250V?
    Where is the NFB?
     
  3. Ten Over

    Ten Over Tele-Holic

    Posts:
    742
    Joined:
    May 13, 2015
    Location:
    Central California
    Most likely your meter itself is causing the low voltage. The 1M input impedance of your meter is in parallel with the bottom 2.2M which makes the voltage divider 2.2M / 688K. Once you remove the meter probe, the voltage will be normal. What is the voltage on pin 8?
     
    Last edited: Aug 23, 2020
    Tom Kamphuys likes this.
  4. mooncat

    mooncat TDPRI Member

    Posts:
    6
    Joined:
    Oct 7, 2019
    Location:
    uk
    Thanks yes thats what I'm talking about.
    The voltage at the top of them is 270 volts the NFB is the top 2.2m resistor as well as a voltage divider acording to robrobs web site. Screen Shot 2020-08-23 at 20.13.56.png

    The voltage on pin 8 is 130volts.
    I'm using a cheap DVM so that may be the case, do you have any suggestions on the best way to measure the voltage or do i need a better DVM?
     
  5. Ten Over

    Ten Over Tele-Holic

    Posts:
    742
    Joined:
    May 13, 2015
    Location:
    Central California
    Everything is fine. You don't need to measure pin 7.
     
    D'tar likes this.
  6. mooncat

    mooncat TDPRI Member

    Posts:
    6
    Joined:
    Oct 7, 2019
    Location:
    uk
    Thanks
    I was wondering if it was something not to be concerned with, as all the other voltages were correct and its working fine, but i thought I best check.
    Thanks for your help.
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.