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Thread: power supply cap values

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    Supporting Member Randall's Avatar
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    power supply cap values

    I am working on a 1972 Ampeg V2. I got a cap kit from Fliptops and they don't all agree with this amp for values, heck neither does this schematic. C17 is good, but the other two can caps are different. At C20 the schematic shows 70/40 @ 450v, but this one has 70/40/40 @ 450v, with 70/40 tied together in place of the schematic's lone 70uF. He sent me a 70/40/40, so I will follow the amp. Now, at C19 the schematic has 40/20/20 @ 450V all tied together for a total of 80uF. I don't know what is in the amp since it was printed on a sticker that is unreadable now. Fliptops sent me a 70/40 @ 450v, can I simply tie those togther and be OK with a total of 110 uF?

    I realize Ampeg made a lot of changes on the fly. I'm not sure what Fliptops intentions are here with which caps go where, but shouldn't I be able to go over a little at that position?

    And another thing, why are we putting almost 600 volts on 450v rated caps?

    https://ampeg.com/support/files/Sche...20Version).pdf

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    Supporting Member mozz's Avatar
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    Use the 70/40 for the 70/40. use the 2-40's to make the 80.

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    Senior Member Old Tele man's Avatar
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    Did you miss the lower 450WVDC cap (C20) to ground? It forms a 450VDC+450VDC "series-stack" for 900WVDC rating...well above 594VDC.

    The 3 caps comprising C19 add up to 80mfd, which in series with the bottom C20 70mfd cap, yields an effective 35+mfd...at 900V capability.

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    Last edited by Old Tele man; 02-14-2019 at 02:13 AM.
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    Stray Cap DrGonz78's Avatar
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    Quote Originally Posted by Randall View Post
    And another thing, why are we putting almost 600 volts on 450v rated caps?
    The caps are all in series so you get voltage rating added together. 900v.

    Edit: simulposting

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  5. #5
    Supporting Member Randall's Avatar
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    "Use the 70/40 for the 70/40. use the 2-40's to make the 80."

    That would leave an unused 70uF, I wouldn't think that was the intention.

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    Don't forget the joker g1's Avatar
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    If you are positive you are following the wiring right, and C20 was 110uF (combo), then the unreadable C19 will have been 100uF.
    So sounds like no 70uF values were used in this amp and the version 2 cap kit would have been a better match.

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    Quote Originally Posted by Randall View Post
    At C20 the schematic shows 70/40 @ 450v, but this one has 70/40/40 @ 450v, with 70/40 tied together in place of the schematic's lone 70uF. He sent me a 70/40/40, so I will follow the amp. Now, at C19 the schematic has 40/20/20 @ 450V all tied together for a total of 80uF. I don't know what is in the amp since it was printed on a sticker that is unreadable now. Fliptops sent me a 70/40 @ 450v, can I simply tie those togther and be OK with a total of 110 uF?
    You could, but now you are missing a 40uF for C18.

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    Supporting Member Randall's Avatar
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    "If you are positive you are following the wiring right, and C20 was 110uF (combo), then the unreadable C19 will have been 100uF.
    So sounds like no 70uF values were used in this amp and the version 2 cap kit would have been a better match."

    This is getting confusing, and maybe I have been unclear. In this amp C20 is 70/40/40. One of the 40s is tied to the 70 and wired as drawn. The other 40 is wired as drawn. We don't know what C19 is, in the amp, but we do know they are all 3 tied together as drawn. I have a new 70/40/40 and 70/40. to replace C19 and C20. What is the best way to do this?

    "You could, but now you are missing a 40uF for C18."

    No, I don't think is the case.

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    Sorry about the confusion, when I said 'no 70uF values were used', I meant they were not used as 70's.
    You said the 70 was tied to the 40 in your amp, so it is used as a 110uF. It is not 'wired as drawn' because the 70 & 40 in the drawing are not tied together.

    The confusion is because we are referring to an incorrect drawing. You should edit a picture of it so it matches your unit.
    What does the existing amp have where C18 is shown? (in series totem pole arrangement with the 40 that is not tied to the 70)

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    Supporting Member Randall's Avatar
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    "What does the existing amp have where C18 is shown? (in series totem pole arrangement with the 40 that is not tied to the 70)"

    C18 is a seperate cardboard covered 20/20 with them tied together. He sent a 47uF/500v for that one.

    If I use the 70/40/40 to replace the 70/40/40 that is in there now (with one 40 tied to the 70), then that leaves me with a 70/40. I think my original question was, is there any reason not to tie them together to get 110uF and put it where the 40/20/20 is now?

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    Last edited by Randall; 02-14-2019 at 10:42 PM.
    It's weird, because it WAS working fine.....

  11. #11
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    Ok. I was not aware he had sent you something for C18, that's why I thought you would be short of a 40uF.
    Yes you can do the combination as you have outlined, no reason not to.

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