Help with Vintage Oscilloscope Capacitors

Discussion in 'Solid State' started by Ricktptman, Jun 18, 2017.

  1. Ricktptman

    Ricktptman There are two kinds of Music: Good & Bad-Ellington Subscriber

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    I'm restoring a vintage O-scope and its brightness isn't quite where I think it ought to be yet. I'm not a recap and ask questions later kind of restorer. (But I'll do it if I see that that it needs it.) I've only had one or two pieces of gear malfunction because of bad caps, so owing to experience, I wait until there's a problem before I go that route. There are some questions that I'd like to get advice on before I start wading into it.

    The first indicates THIS entry in the SM:

    "40 + 40MF 315V". (x2) Electrolytic
    What does this mean?

    I know that having a slightly greater voltage rating is a good thing, but I've read that you need to stay pretty close to the capacitance ratings. In the machine, I find these: (They look like electrolytics, FWIW.)

    One set of caps: .2uF 1kV
    Other cap: .2uF 2kV

    BUT the SM says these caps are supposed to be

    .1uF 1.4kV (first set)
    .1uF 1.5kV (the individual one)

    Will they sub out for each other? (I know this much, they're not easy to find.)

    Thanks in advance for any help. My experience with CRT's is very limited. This isn't in my traditional wheelhouse.
     
  2. NAD80

    NAD80 Super Member

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    The capacitance should be the same, but the higher voltage rating is better. Possible undocumented production changes. What scope are you restoring?
     
  3. Ricktptman

    Ricktptman There are two kinds of Music: Good & Bad-Ellington Subscriber

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    Pioneer SD-1000. There are no burns or spots on the CRT. (Even at the yoke.) It looks so close to NOS it's scary. (True for most of the machine, except for a bit of dust fog on the FP-it cleaned right off.)
    Maybe it was never THAT bright to begin with.....This is the first 1000 I've owned. I have seen a couple of 1100's but it was many years ago. It's not HARD to see, I'm just used to my '90's vintage dual trace.
    Back in the day, I'm not sure they were that super bright anyway.....trying not to (no pun intended) "gaslight" myself about it....thanks!
     
  4. elnaldo

    elnaldo Addicted Member

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    It's a double capacitor, two 40uF x 315Volt in one can. The "x2" could mean "two" capacitors, I don't think it means "X2" safety capacitors, but double check the position in circuit. "X2" safety caps are usually connected across the AC line and they are usually small film or ceramic caps, like 0.47, 0.22 or even o.o22 uF.
     
  5. Ricktptman

    Ricktptman There are two kinds of Music: Good & Bad-Ellington Subscriber

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    Thank you for your reply. If somebody's been down this road before I'd sure appreciate any help/assistance. I know CRT's age and I know hours powered up affects them. For me, it's just a matter of figuring out how much improvement can realistically be expected. Thanks again!
     
  6. Ricktptman

    Ricktptman There are two kinds of Music: Good & Bad-Ellington Subscriber

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    I may have some helpful news on this topic/these vintage O-Scopes. If what I'm trying pans out, I think it will be of interest to those who have these machines. If it works, I'll post a new thread. I'm trying two approaches. I'm delaying the Recap for a bit. But thanks again to everyone for posting.
     
  7. Ricktptman

    Ricktptman There are two kinds of Music: Good & Bad-Ellington Subscriber

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    It turned out that even though the machine lived a very sheltered existence, the CRT was in the last 10% of its life. I kept it. It's in my living room with some vintage photography "accent" fiddly bits. The 1K's doing fine now. I lucked into a NOS tube. The recap's not necessary. Thanks again to everyone who responded.
     

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