Blonde Circuit Bassman Filter Cap Values?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by mt10, Jun 9, 2006.

  1. mt10

    mt10 Member

    Messages:
    30
    Joined:
    Dec 31, 2005
    Location:
    Seattle
    Can anyone tell me the correct filter cap values for a 6G6-B blonde circuit Bassman? I bought one that has a mix of new and old filter caps but the newer ones looks suspiciously high.

    Would the filter caps be the same on a 6G6-A also?

    Thanks
     
  2. Dave C

    Dave C Gold Supporting Member

    Messages:
    1,360
    Joined:
    Jun 10, 2005
    Location:
    Waterford Ct
  3. slider313

    slider313 Silver Supporting Member

    Messages:
    7,432
    Joined:
    Jul 28, 2005
    Location:
    NC
    Schematics show 600 volt caps, but Fender used some 525 and 550 volt caps over the years. I recently came across an early '62 Fender Concert that had 525v caps,yet any schematic I've seen shows 600v.I recapped using two 100uf at 350v in series with a 220k 1 watt resistor across each cap. This gives you 50uf at 700v.
     
  4. billdurham

    billdurham Member

    Messages:
    293
    Joined:
    Dec 29, 2005
    The 6G6-B caps were all 20uf @ 600V. This changed with the AA 165 BF circuit to 20s at 450 except for the first caps after the rectifier, which were 2 70uf@350v caps in series.

    BD
     
  5. slider313

    slider313 Silver Supporting Member

    Messages:
    7,432
    Joined:
    Jul 28, 2005
    Location:
    NC
    What do you mean when you say the "newer" ones look suspiciously high?
    Do you mean the uf value? The newer 600v caps do not fit in the tray.
     
  6. mt10

    mt10 Member

    Messages:
    30
    Joined:
    Dec 31, 2005
    Location:
    Seattle
    Thanks everyone. When I was saying the new ones look suspiciously high, I as referring to the uf value. What is in there now are 2 200uf in series. I think I'll go with slider313's 2 100uf at 350v in series and rest 20uf at 525v since that is what was originally in it.

    A followup question, the amp actually sounds great now, if I change the 200uf caps to 100uf caps, it should go from a tighter sound to a looser sound, is that right? Higher filtering means a tighter sound?

    Thanks
     
  7. slider313

    slider313 Silver Supporting Member

    Messages:
    7,432
    Joined:
    Jul 28, 2005
    Location:
    NC
    You most likely wouldn't hear the differance unless you have the amp dimed,where ripple current may make the notes sound slightly out of tune or have ghost notes with the notes your playing.I think you could leave the 200uf's in and change the 20's to 20/500.
     
  8. billdurham

    billdurham Member

    Messages:
    293
    Joined:
    Dec 29, 2005
    MT10,

    The 2-200uf's in series I'm sure are the first caps after the rectifier. The reason they are in series is to get the voltage rating high enough to handle the peak voltage out of the rectifier. The caps in series half the capacitance and double the voltage rating. So you have with the pair a 100uf, 700v cap. The 6G6-B I just sold to Flicker180 had 2 70uf @ 350v in series. The original 6G6B schematic had two 20uf @ 600v in parallel in that first position. That would give you an equivalent to a 40uf @600v. So, anything above the 40uf value would be fine and since its before both the choke and the output tranny, shouldn't have that much effect on the tone quality of the amp. The ghosting issues not withstanding, overall tone shouldn't change that much as long as you are above the 40uf.

    BD
     

Share This Page