Which caps to replace?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by alderbody, May 18, 2006.

  1. alderbody

    alderbody Member

    Messages:
    682
    Joined:
    Oct 14, 2004
    Location:
    overseas
    [​IMG]

    This is the schematic of my amp (135W MV twin reverb).

    In case i want to replace some caps in there, which ones would make a difference?

    Some people say that there's no clearly audible change if i replaced the ones in the tone stack. Not even the ceramics with silver micas?

    Could someone pinpoint the coupling caps, or any cap that could be replaced?

    I'd like to go with Mallory 150's because i really like them in my custom built pedals, although they are mostly suited for "Marshall type" amps.
     
  2. tonezoneonline

    tonezoneonline Member

    Messages:
    437
    Joined:
    Dec 15, 2003
    Location:
    central Illinois
    Not trying to be a smartass but this is one of those cases where "if you don't know you probably shouldn't be messing with it".If you must ,you should first make sure the filter caps are all good.Then figure out what you want from the amp and proceed from there in place of just blindly changing caps.
    What kind of changes would you like to see in the amps tone?What are you trying to do with it that it won't do?
     
  3. Steve Dallas

    Steve Dallas Supporting Member

    Messages:
    8,205
    Joined:
    Feb 22, 2005
    Location:
    Surrounded by Idiots
    I wouldn't change a thing in that amp. If you have a Black or Silver amp (or a Rivera built version), you already have some great caps in there. Nothing wrong with Blue Drops at all.

    Mallory 150s are very neutral sounding. Orange drops are more refined and hi-fi. SoZos are more British sounding with a darker and smoother tone (with a little graininess mixed in just for fun).

    Just play the sucker and don't worry about the caps!
     
  4. alderbody

    alderbody Member

    Messages:
    682
    Joined:
    Oct 14, 2004
    Location:
    overseas
    The filter caps have already been replaced a couple of years ago.

    Also, the Ultra-Linear feature of the OT has been removed (that's what the tech said) and some other minor tweaks were done.

    The sound seems to be harsh and flat, especially in the "vibrato" part of the amp. (of course this is the place where the tech did all the tweaks, so i guess asking for an "undo" could be better...)

    The amp doesn't like most of the pedals and when treble is increased i get a flat, harsh and metallic tone.
    Not quite musical in any way.
    It's pity to see a small solid state Marshall to kick this amp's ass in almost every aspect, except headroom...


    I know that the secret in tone about these amps lies in the OT and power supply area, but i thought about "sweetening" the voice a little.

    Just because this amp is way too powerful for my needs, plus where i live the availability of old amps is close to zero
    (i can't easily find another), i plan to replace the OT with a less powerful one and remove the wiring for the two 6L6's.
    This would require a massive "operation" so i still have it under serious consideration...

    So, that's why i thought about replacing a few caps in the first place to see if by any chance i got a better tone before the "main strike"...

    Who knows, maybe i'll find a better amp till then...
     
  5. alderbody

    alderbody Member

    Messages:
    682
    Joined:
    Oct 14, 2004
    Location:
    overseas
    Thanks for the tips on caps!
    I was already familiar with the mallories and the orange drops.
    The sound of the OD's is indeed quite Hi-Fi, at least for me.

    I seem to have found my match in the Mallories after many tests.

    This is my amp:

    [​IMG]

    [​IMG]

    (I had it running at half power at the time the picture was taken)

    It's an early 80's (1980-1982) 135W Ultra-Linear, Master Volume, export model. (selectable voltage)
    If i remember well the caps in this amp are brown. (It's original filter caps were mallory, replaced by sprague)

    When i got this amp it had one f__ked up fender speaker and one almost f__ked up celestion (not for guitar), so i replaced them with new eminence legends. (nothing "super" about them, just decent IMHO)

    If you read the above post you'll see why i started this thread.

    I just manage to "limit" the harshness by plugging in the way shown in the pic...

    :Spank
     
  6. alderbody

    alderbody Member

    Messages:
    682
    Joined:
    Oct 14, 2004
    Location:
    overseas
    How about....

    undoing the tweaks the tech has done (except the de-UL) and get an attenuator in order to be able to crank the amp.

    and maybe a few cap replacements?... :D
     
  7. donnyjaguar

    donnyjaguar Member

    Messages:
    4,243
    Joined:
    Nov 4, 2005
    Location:
    Canada
    If anything I'd say it sounds harsh because of the presence of a capacitor tapped onto the master volume. I can't read the component value or designator on your schematic.
     

Share This Page