Augat WireWrap board with bypass capacitor socket in a strange place ?

Discussion in 'General Electronics Chat' started by PauloConstantino, Sep 17, 2016.

  1. PauloConstantino

    Thread Starter Member

    Jun 23, 2016
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    Dear friends,

    I have bought this Augat board in order to build a circuit, but I have found that the bypass capacitor pins are below each IC ! In other words I can't see a way of attaching them to the circuit!

    Please look at these photos. If I put each IC in its place, they will cover the bypass cap pins. The only chance is to attach the caps below directly to the long pins beneath. But then I will have to solder them which is terrible. I am really confused.

    [​IMG]

    [​IMG]


    The second image is rotated but you can see the IC totally covers the bypass cap space and the gap is very thin - No space for a cap.
    Does anyone know anything about this?

    Best wishes and thanks

    Paul
     
  2. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,958
    387
    First guess: you might be able to fit a disc ceramic folded down on the board under the ICs.
     
  3. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,958
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    Second guess: They are not for bypass capacitors. It is a multilayer board and those pins allow you to connect the power wires to the ICs with short wires.
     
    nsaspook likes this.
  4. PauloConstantino

    Thread Starter Member

    Jun 23, 2016
    121
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    No because there would be no need for the pinholes on top....... They are definitely bypass but in the wrong place. I have seen similar boards with correct placement.

    I cannot believe that they are wrong. Augat are pros. I must be missing something!

    The middle part is even stranger. Here are some photos

    [​IMG]

    [​IMG]
     
  5. PauloConstantino

    Thread Starter Member

    Jun 23, 2016
    121
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    Good guess. I tried but they don't fit! This is so strange
     
  6. be80be

    Senior Member

    Jul 5, 2008
    431
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    You use pins
    http://www.timefracture.org/D16docs/wire_wrap.html
     
  7. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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  8. PauloConstantino

    Thread Starter Member

    Jun 23, 2016
    121
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  9. PauloConstantino

    Thread Starter Member

    Jun 23, 2016
    121
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  10. be80be

    Senior Member

    Jul 5, 2008
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    I told you and you didn't read it. you put pins in them and wire warp it to the back.
    [​IMG]
    nsaspook post is a rat's nest but as you'll find out after trying to stop cross talk from
    trying to not have rat's nest the rat's nest layout works better then parallel rows of wires.
    And one thing you can bind the top down to make the pin lay flat we had them that had flat tops but I have not seen any in years.
     
    Last edited: Sep 17, 2016
  11. PauloConstantino

    Thread Starter Member

    Jun 23, 2016
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    My son.... Can you please be clearer? The bypass capacitor pinholes have pins on the back. There's no need for extra pins... If you mean to attach these long pins on the upperside, directly into the pinholes, then that doesn't work either...
     
  12. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    http://www.arieselec.com/products/data/12026-open-frame-capacitor-collet-socket.htm
    You can use open-frame sockets with pre-soldered caps like this but I've usually soldered in bypass caps on the prototype boards backside directly on the Vcc chip pin to Gnd first before starting the wire-wrap power connections. The whole point of the bypass cap is to keep the unwanted signals off the wrap wires by having the lowest possible inductance to ground through it instead of the wire.
     
  13. RichardO

    Well-Known Member

    May 4, 2013
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    I agree that these pins are to power and ground planes. But I also agree with you that bypass caps should be able to plug into them.

    If your caps don't plug into these pins then I think it is simply that their leads are too large in diameter. The lead must be about the same size as an IC pin. I have used caps that have leads the same size as IC's and are on 0.3" DIP spacing. I find it odd that your pins are 0.4" apart.
     
  14. dl324

    Distinguished Member

    Mar 30, 2015
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    The board must have provisions for multiple DIP package sizes, so you could use caps with lead spacing the same as DIP packages:
    upload_2016-9-19_16-7-54.png
    Or you could use radial ceramics with 0.2" body size.

    You could mount some IC's in sockets so a cap will fit, or dedicate some chip sites to decaps:
    upload_2016-9-19_16-10-52.png
     
  15. PauloConstantino

    Thread Starter Member

    Jun 23, 2016
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    Friends,

    Are there throughhole capacitors with packages thin enough to fit under the gap between the board and an IC ?
     
  16. PauloConstantino

    Thread Starter Member

    Jun 23, 2016
    121
    5

    Why the leads? It's the capacitor itself that is too big, but it's a standard ceramic one. The lead is very thin and can fit anywhere. This board requires a capacitor to be under each IC, and I can't find a capacitor that small. This board is so strange, I think it might have been made for a special purpose...
     
  17. PauloConstantino

    Thread Starter Member

    Jun 23, 2016
    121
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    Can I find those bottom photo caps but in a small enough size to fit in the gap ? That would be a good solution...
     
  18. dl324

    Distinguished Member

    Mar 30, 2015
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    Smallest diameter I've seen is about 0.1"; too large to fit under an IC package unless you put it in a socket. That might give enough clearance for a cap to fit.
    upload_2016-9-19_20-4-26.png
    SA05 package (grid is 0.2"):
    upload_2016-9-19_20-11-41.png

    I've never seen a design that actually put a bypass cap on each IC.

    Another option is to use surface mount caps on a small, thin board to roll your own.
     
  19. Sensacell

    Well-Known Member

    Jun 19, 2012
    1,132
    267
    Just get some 0805 size SMD caps and some copper foil shielding tape.

    You can make your own "traces" with the foil tape, the 0805 caps will fit nicely under the sockets.
     
  20. DickCappels

    Moderator

    Aug 21, 2008
    2,659
    632
    I think we can all agree that the whole point of bypass capacitors in high speed digital logic is to present a low impedance to the logic circuit. For that reason, even when using wire-wrap boards I always soldered the capacitors into place on the side of the board opposite the IC sockets. Adding extra wire, and wire that might be more than a straight line is antithetical to a bypass capacaitor's purpose.
     
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