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

Thread Starter

PauloConstantino

Joined Jun 23, 2016
266
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.






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
 

AlbertHall

Joined Jun 4, 2014
10,423
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.
 

Thread Starter

PauloConstantino

Joined Jun 23, 2016
266
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.
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



 

Thread Starter

PauloConstantino

Joined Jun 23, 2016
266

be80be

Joined Jul 5, 2008
2,049
I told you and you didn't read it. you put pins in them and wire warp it to the back.

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.
 
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Thread Starter

PauloConstantino

Joined Jun 23, 2016
266
I told you and you didn't read it. you put pins in them and wire warp it to the back.

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.

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...
 

nsaspook

Joined Aug 27, 2009
7,610
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.
 

RichardO

Joined May 4, 2013
2,271
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.
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.
 

dl324

Joined Mar 30, 2015
11,593
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.
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
 

Thread Starter

PauloConstantino

Joined Jun 23, 2016
266
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.

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...
 

Thread Starter

PauloConstantino

Joined Jun 23, 2016
266
The board must have provisions for multiple DIP package sizes, so you could use caps with lead spacing the same as DIP packages:
View attachment 112236
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:
View attachment 112237

Can I find those bottom photo caps but in a small enough size to fit in the gap ? That would be a good solution...
 

dl324

Joined Mar 30, 2015
11,593
Can I find those bottom photo caps but in a small enough size to fit in the gap ? That would be a good solution...
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.
 

Sensacell

Joined Jun 19, 2012
2,598
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.
 

DickCappels

Joined Aug 21, 2008
6,594
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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