Correct way to bend through-hole leads

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boji

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Most assembly manuals advise you create spaCe in the crook of a thru-hole part that will stand upright (see picture).

Why?

T54tXP2.jpg


Edit: Changed title of thread for search posterity.
 
Don't bend a lead AT the body. You crack the seal or break it off. Clamp needle-nose pliers on the lead near the body, bend the free lead.
 
there are billions of bent leads out there, some do not even bother with the needle nose if they are in a hurry, witness the caps,

best to bend negative lead instead of positive on polarized caps so plus lead does not lay against negative charged can,

if you build a discrete API opamp, you will probably be stuffing parts vertically.

remember the painted leads on resistors? always wondered how they did that.
 

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Appreciate all of your input.  Didn't want to assume the only concern was fatigue, as I've not seen a lead's seal crack from thumbing it around and down. Never went so far as to inspect them under a scope, however.

How do you grip the lead to make a tight bend without touching the package?
NOT like PRR advises!  :-[  My caveman hands treat TO-92's with a softer touch tho, what with that heat-joined seam.

best to bend negative lead instead of positive on polarized caps
Thank you, this is good to remember.  Got a bit of the reverse issue presently...have a hankering for Silmic II's but they are only sold radially.

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I think I read a nasa or military thing one time that said use a cocktail stick ,or some thing of equivalent diameter to bend the component leads around , apparently its  better with a little radius on the bend than than sharp square right angle , as there would be less stress /fatigue in the lead material . I guess those guys noticed how things could fail under extreme conditions , of vibration and g force. Ive seen a little gadget on fleabay , its a plastic lead former with graduated lead lenght and the appropriate radius bend .  I find the shaft of a precision screw driver the most convenient thing to use , but on some ocassions particularly if the lead wire is heavy duty I do as PRR described .
 
I have posted this elsewhere, but if you want to be a rocket surgeon here is the NASA spec:
https://workmanship.nasa.gov/lib/insp/2%20books/frameset.html

It is a truly humbling read  ;D
 
mjrippe said:
I have posted this elsewhere, but if you want to be a rocket surgeon here is the NASA spec:
https://workmanship.nasa.gov/lib/insp/2%20books/frameset.html

It is a truly humbling read  ;D
Back in the 60's I worked on a navy project at MIT-IL and was required to meet mil-spec soldering standards.

JR
 
If you google "lead forming tool for resistors" you will see pictures of a wide variety of lead forming tools, designed to accommodate many package sizes and many lead spacings. I've only used them briefly, choosing instead a round jaw pliers most of the time, but then gain, I use mostly SMD components and not through-hole axials that need lead prep. I have a friend who does through hole assembly for a guitar pedal manufacturer, and he likes using a lead forming tool to get super consistent results.
 
Thanks again for additional comments, gents.

Lots to learn from that document .  Thanks for posting .
+1

Enjoying Chapter 6.  Humbling indeed...I'm guilty of quite a few improper process controls.
UNACCEPTABLE!  

Edit:
Camel humps? You amp repair guys ever see these in the real world?

2RB70v9.jpg




 
Since we're on the topic of standards, I've seen some amp builds where lytics are hot glued in place. Is this purely a mechanical concern or do caps sometimes exhibit microphonics?
 
Somewhere in chapter 6 they mention about securing components to the board only of its over a certain number of grams , the hot glue or sometimes sillicon rubber or contact adhesive you see on electrolytics prevents you relying on the solder joint to support the weight of the component , its definately an extra insurance against any vibrational modes that might occur also .
 
boji said:
Since we're on the topic of standards, I've seen some amp builds where lytics are hot glued in place. Is this purely a mechanical concern or do caps sometimes exhibit microphonics?
Back last century at Peavey, we had a shaker table where we could stress test PCB components for shaking. I preferred Mylar film to electrolytic caps for fractions of a uF so would sometimes end up with fairly massive film caps in my designs. Rather than find the caps rolling around loose in the bottom of the chassis after an overnight shake , I would have the factory apply hot melt to provide mechanical support for relatively massive capacitors. 

So to answer you question.. its mechanical.

BTW you can test for microphonic components (pretty rare) by tapping the components with the eraser end of a pencil, while gain is WFO... I can count on fingers of one hand how many I've found over the decades.

JR
 
to support the weight of the component
-------------------------------
to answer you question.. its mechanical.
Thank you both!

Test for microphonic components (pretty rare) by tapping the components with the eraser end of a pencil, while gain is WFO
When you put it that way, seems like a pretty obvious test should the problem ever come around. More good advice!

Made me think of Guitarologist's complaints about  Korg's nutube:
https://youtu.be/raYGrKWSKRE?t=866
 
JohnRoberts said:
BTW you can test for microphonic components (pretty rare) by tapping the components with the eraser end of a pencil, while gain is WFO... I can count on fingers of one hand how many I've found over the decades.

An occasional odd one is the microphonic disc cap.  Found a few in Fender amps.  Though I prefer to tap using a wooden chopstick - pencil erasers have that metal band around them...
 
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