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Thread: New (to me) amps

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    Senior Member quindecima's Avatar
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    New (to me) amps

    I have been looking for amps for my system and finally found a couple, they arrived today. they are Adcom 555II's. They arrived well packaged and the condition is way above usual. I am going to do some mods on these. First thing I did was fire them up and check the MV across the speaker terminals. They are fine and were dead quiet when I fired them up. I am going to do all stages and the first is the PS. I will post as things progress.

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    Senior Member quindecima's Avatar
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    So far so good. I had to look hard to find 4 caps in the PS but I finally found them under the plate that holds the bridge rectifier and bleeders on. It's the only place they could be after looking at it. They were 100nf at 100v and I replaced them with 100nf at 250V I'm waiting for some X2 caps for the AC line and the new bleeders and that part will be pretty much done. I'm going to change the bridge from 25amp at 400v to 50 amp at 600v, Bleeders from 3.9Kohm at 3 watt to 4.7Kohm at 7 watt overkill but they were available. I'm going to filter the AC side of the bridge with a 10nf at 400v X2 cap. Not present now.
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    What's (as in function) 100nF (.1uF)?

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    Senior Member quindecima's Avatar
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    Yes

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    Quote Originally Posted by quindecima View Post
    Yes
    What is their function?
    I am asking as I thought I understood you to mean re-capping/rebuilding when you wrote "I am going to do all stages and the first is the PS"

    What are the values of the big cans?

    Nice amps, you get them for a good price?

    I have plenty of .01uF X1/Y2 caps if you need a few (rather than pay shipping on an order so small)

    Thomas

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    Senior Member quindecima's Avatar
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    They are bypassing caps.

    The big cans are 100v at 15000uf

    I would be better off with the X2 caps their voltage rating is less than 2500v while the X1 is 2500v and below 4000v but.........are they long lead? Whats the voltage?

    I got them for a good price, condition is everything on these. about 100 to 150 less than they go for on Epay.

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    Quote Originally Posted by quindecima View Post
    I would be better off with the X2 caps...............
    I don't understand but that's "OK"

    I'll post the specs on the ones I have in a few, I have two lead types as well, one dressed short for PC board work and the other batch with longer leads

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    Here's the types I have. The listings have a link to the data sheets for each device. The TDKs have short kinked leads which I just straighten out and use where they'll work. Don't know why a device with leads like this was sold loose (a little on the short side, I missed it when I ordered them, I believed the "pic"):
    http://www.mouser.com/Search/Product...CS17-F2GA103MY

    http://www.mouser.com/Search/Product...81-DE2F3KH103M

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    Senior Member quindecima's Avatar
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    Thomas,

    The voltage is too low and they are ceramic, not what I am looking for but thanks you for the offer.

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    Quote Originally Posted by quindecima View Post
    Thomas,

    The voltage is too low and they are ceramic, not what I am looking for but thanks you for the offer.
    Too low? They are X1/Y2 impulse rated (that's a 4000V and 5000V respectively) 2600V for the TDKs

    What are you using these for?

    I don't think you're going to find any X1/Y2 Class Certified products in anything but ceramic:
    http://www.mouser.com/pdfdocs/Safety.pdf

    I really am curious though, just exactly where are these going in the circuit (what are they doing)

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    Senior Member quindecima's Avatar
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    That's the pulse rating not the steady voltage. The steady V on those is 275V I would like at least 380V. The purpose is to filter the HF noise on AC. I have found them in mica but it is the long leads that are the problem

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    Quote Originally Posted by quindecima View Post
    That's the pulse rating not the steady voltage. The steady V on those is 275V I would like at least 380V. The purpose is to filter the HF noise on AC. I have found them in mica but it is the long leads that are the problem
    The TDKs are rated @ 400VAC

    What is the lead length you need? These caps are the types used by builders for line noise suppression/filtering, ie: radios/receivers, have worked well for me

    Good luck, hope you find what you need

    Thomas

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    Senior Member quindecima's Avatar
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    Ceramic caps act like a microphone amplifying AC noise that's why I would rather use Film.

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    Senior Member quindecima's Avatar
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    O.K. here's the current situation. The caps are going across the secondary of the main transformer so I don't need X2 caps there, a short there would not be as catastrophic as one across the mains. I will put a new one across the mains because the one there now is ceramic and I don't need the long leads.

    I finished the PS stuff this morning and fired the amp up. I will do this after I work on each stage so if I screw up I will know where I did it. It's sitting here now dead quiet.
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    Senior Member quindecima's Avatar
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    Here we are today. The X2 caps I tried to get with the long leads actually came with them, not as described at all. I replaced the little caps you see that are 47uf at 160V with 120uf at 200V and bypassed them with 22uf at 600V orange drops. I also replaced the Ceramic bypass cap on the mains with one of the X2 caps. I am debating if I need to get to the bottom of those 4 boards to replace the 68pf at 500V film that are there with the same thing.

    Addendum. I replaced the film that were there with Micas.
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