SET Tube Issue: Anyone Advice or Insights

Discussion in 'DIY' started by Darkstar1, Aug 20, 2021.

  1. Darkstar1

    Darkstar1 Facebook Friend

    Contributor
    Joined:
    Mar 30, 2019
    Likes Received:
    107
    Trophy Points:
    33
    Location:
    Brooklyn, NYC
    I am looking for any help or guidance. Any help is much appreciated. I am tying to learn about electronics and tube amps in general. In the process of reading up. I Ordered tools and probably started exploring too early but felt I knew the safety precautions so I proceeded.

    Situation.

    I have a Quicksilver HPA Tube Set amp. Utilizes 12AX7 input tubes (1 per channel) and 6BQ5 output tubes (1 per channel). I liked the amp so I decided to upgrade starting with the coupling caps. I replaced the .12uf 400 VDC (quicksilver branded) with Jupiter Caps .15uf 600v caps. The results were good and the amp didn't act up. thought I was ok by keeping uf value close as possible but getting more volts.

    I then chose to remove the alps pot. I tried to install a super nice TDK volume pot but it was too big. I ended up gong with a smaller (in size) 100 ohm TDK pot. I soldered it in place. Started to play music and it was sounding quite nice. I ended up turning off the amp and heard a zap and saw the residual light come under the case. Upon closer inspection I have fried two resistors on one of the 6BQ5 output tubes. They appear to 5 band 570ohm 1% in value. First one is attached to PIN 3 and 4 so by my research (3 pin Cathode and grid 3) and (4 pin filament). The other resistor appears to be on pin 3 and pin 5 which is also a filament.

    I reached out to QS audio to see if he would sell me the resistors. I also checked some of the normal supply websites and it seems these resistors are not stocked.

    What did I do?

    I kinda feel that I may have pushed the resistors into contact causing them to fry while working on amp.

    Or did I wire the TDK volume pot up wrong (does not seem so but not ruling it out)

    Or did I change values so much that I caused this?

    [​IMG]

    [​IMG]
     
    • Like / Agree Like / Agree x 2
    • List
    Last edited: Aug 20, 2021
  2. Darkstar1

    Darkstar1 Facebook Friend

    Contributor
    Joined:
    Mar 30, 2019
    Likes Received:
    107
    Trophy Points:
    33
    Location:
    Brooklyn, NYC
    update:

    Quicksilver gave the specs of the Resistors. Ordered from parts house and replaced resistor and everything works well. Lesson learned be carefully pushing stuff around to mod point to points amps. I must have pushed the leads together causing a short.
     
    • Like / Agree Like / Agree x 3
    • List

Share This Page