Tremolo too fast on 68 Super

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by kingsxman, Mar 28, 2008.

  1. kingsxman

    kingsxman Silver Supporting Member

    Messages:
    6,565
    Joined:
    Nov 8, 2004
    Location:
    Minnesota
    I have a Silverface blackline 68 Super Reverb that I recently picked up and the tremolo seems not right to me. I have to run the speed at 1 and even then its probably modulating at a speed of about 140-150 bpm. This doesnt seem normal. I would think I shoudl be able to get a very slow modulation out of this. Just not possible as i sits now. I've tried swapping tubes but no go. I'm wondering if that "bug" chip inside is what controls the tremolo modulation. I've ordered some replacment speakers so I'll be pulling the chassis soon. Just wondering if I should pick up one of those chips and swap it while I've got the head open.

    If so..any recommendations on what chip to use and where to get it?

    thx
     
  2. Blue Strat

    Blue Strat Member

    Messages:
    30,036
    Joined:
    Aug 2, 2002
    Location:
    Sterling, VA (not far from Washington DC)
    You need to replace or increase the values of the capacitors in the oscillator circuit. There are 3 disc caps in a row just to the left of the "bug" (while facing the front panel of the amp). Two of them should all be .01uf caps. 2 (I can't remember which 2, possibly the 2 closest to the front panel) are the ones to replace. If you replace all 3 you can't go wrong. Replace them with .02uf caps and you'll get half the normal speed which is typically a good mod even on trems that are working normally.

    Also, check the resistors in that area to see if their values have shifted significantly. If they have, replace them.
     
  3. kingsxman

    kingsxman Silver Supporting Member

    Messages:
    6,565
    Joined:
    Nov 8, 2004
    Location:
    Minnesota
    Thanks Mike! Do you know what voltage they are? Just looks like normal ceramic caps. Does the voltage matter?
    thx
     
  4. kingsxman

    kingsxman Silver Supporting Member

    Messages:
    6,565
    Joined:
    Nov 8, 2004
    Location:
    Minnesota
    I am having a hellova time finding these caps anywhere. My local AEI store didnt have them, now I'm checking on line. Anyone have any good recommendations?
     
  5. Blue Strat

    Blue Strat Member

    Messages:
    30,036
    Joined:
    Aug 2, 2002
    Location:
    Sterling, VA (not far from Washington DC)
    400Volts will definitely work.

    www.mouser.com will have them and so will www.mojotone.com . If all else fails, use higher quality caps like Orange Drops. They're easy enough to find in .02uf.
     
  6. kingsxman

    kingsxman Silver Supporting Member

    Messages:
    6,565
    Joined:
    Nov 8, 2004
    Location:
    Minnesota
    Thanks Mike. These look like ceramic caps but ceramic caps only seem to come in values up to 100v. How important is that voltage rating on these?
    I actually have some .022 ufd caps that are similiar to orange drops but I dont know the voltage rating on them.

    Here's a link to my circuit board. You can see the "large" ceramic caps that are on it now.

    http://users.goldengate.net/~jgermann/superreverb_circuitboard/superreverb_board2.JPG
     
  7. Blue Strat

    Blue Strat Member

    Messages:
    30,036
    Joined:
    Aug 2, 2002
    Location:
    Sterling, VA (not far from Washington DC)
    Voltage rating is important. Not sure exactly how much you need, but 400 will definitely cover it.
     
  8. doctorx

    doctorx Member

    Messages:
    4,265
    Joined:
    Jun 10, 2004
    Location:
    8 miles high
    Mike is right, I have done this on a couple of my Fenders and it slows the trem down nice. I think I used 400 volt orange drops.
     
  9. kingsxman

    kingsxman Silver Supporting Member

    Messages:
    6,565
    Joined:
    Nov 8, 2004
    Location:
    Minnesota
    Thanks Doc. Did you replace all 3?

    Sounds like orange drops might be the way I have to go to get the voltage.
     
  10. doctorx

    doctorx Member

    Messages:
    4,265
    Joined:
    Jun 10, 2004
    Location:
    8 miles high
  11. kingsxman

    kingsxman Silver Supporting Member

    Messages:
    6,565
    Joined:
    Nov 8, 2004
    Location:
    Minnesota
    Great link. Thanks.

    I'll have to check what I have at home. I have some Mallorys but not sure of the value or voltage rating. My speakers will be in today and I'd like to make this change tomorrow night and NOT have to wait for parts via the mail (and take the head out yet again of the chassis). :)

    What I do have is some .022 ufd metal film (I believe) caps...but once again I cant tell the voltage rating. Arent the mallory's more of a can style?
     
  12. kingsxman

    kingsxman Silver Supporting Member

    Messages:
    6,565
    Joined:
    Nov 8, 2004
    Location:
    Minnesota
    Thanks All. I DID have 1 mallory .022 ufd 600v cap. I replaced the 1st of the caps (towards the front panel I believe) and that did the trick. The tremelo is at a very good tempo now. What a difference. I wonder what replacing the middle one would have done to the sound?

    Thanks again for your help everyone.
     

Share This Page