Possible to repair a loose potentiometer leg?

[rjb]

Both rjb and I have done so due to the fairly complex and cramped wiring on the push-pull switches.

Hey, leave me out of this!
I agree; for electronic hand soldering, 3 seconds is an eternity.
If you have to hit the lug more than once, let it cool between hits.
Just don't use a blow torch, figuratively speaking.
I just ordered a cheap "variable temperature" station (really just variable wattage- no thermostat).
Hopefully good enough for rock 'n' roll.

-rb

[dchang0]

Hmm. You bring up an important point. 3 seconds isn't how long it takes for our hotter-than-spec soldering irons to damage the legs.

The Bourns pot was probably already damaged in under a fraction of second with my 450C iron attaching just the first wire. If I hang out there attaching more wires, it doesn't matter--the damage was already done.

Put another way, going faster or allowing cool-downs is probably not going to save me if my iron is way too hot.

[dmeek]

I originally modified these pliers for pulling and installing power cord strain reliefs and they work very well for that.
They're also good for crimping rivets.


http://music-electronics-forum.com/a...1&d=1502048441

[dchang0]

Wow! How did you grind away all that material? (What tool, what kind of blade/wheel/drum/file?)

[rjb]

Does the heat cause the solder leg to expand too much, from which it fails to contract fully? Or is it that the heat damages the carbon traces? Or something else or a combination of factors? Put another way, I am wondering if re-crimping will permanently solve this...

This still bugs me.

I recognize that Bourns' "soldering condition" spec is 260C(500F) max for 3 sec max.
I've learned from experience that ~700F(~370C) for ~1 sec can loosen a leg.
But I don't understand why 700F would loosen a riveted connection.
Admitedly, I know zippety-doo-dah about metallurgy.
Can someone explain? Or at least offer a hypothessis?

Thanks,
-rb

[Thoriated Tungsten]

This still bugs me.

I realize that Bourns' "soldering condition" spec is 260C(500F) max for 3 sec max.
I've learned from experience that application of ~700F(~370C) for ~1 sec can loosen a leg.
But I don't understand why 700F would loosen a riveted connection.
Admitedly, I know zippety-doo-dah about metallurgy.
Can someone explain? Or at least offer a hypothessis?

Thanks,
-rb

The rivet is perfectly fine. It is the phenolic(?) baseboard to which the rivet is attached which softens when heated, thus taking the tension out of the riveted connection.

[dchang0]

So this means it is possible to melt the baseboard by putting a soldering iron directly on it or warp it by using a heat gun--ugh. (They've gone too far in cutting corners to save a few pennies.)

[rjb]

The rivet is perfectly fine. It is the phenolic(?) baseboard to which the rivet is attached which softens when heated, thus taking the tension out of the riveted connection.

Well now, that sounds pretty obvious, doesn't it? D'oh.
<sincere>Thanks. Now I can sleep at night.</sincere>

-rb

[rjb]

So this means it is possible to melt the baseboard by putting a soldering iron directly on it or warp it by using a heat gun--ugh.

Why would you do either of those?
Use your pinky to steady your soldering iron hand.*
For heat shrink, use a hair dryer. Just don't let your significant other catch you.

(They've gone too far in cutting corners to save a few pennies.)

I don't know how, or if, Bourns' substrate differs from traditional pots.
Is it different than that used in the 82 series polymer conductor pots, rated at 750F?
So many questions....

In regard to having to use a low-temp iron for 17mm push-pull pots, I see it as a trade-off for miniturization and convenience. The push-pull switch takes the place of a toggle or slide switch that would have taken up real estate and/or "gotten in the way". <whine>Of course, its not very convenient when you have to replace/rewire a DPDT switch because you trashed its associated pot. Again. I just wish I had known the temperature constraint before wasting so much time on what should have been a quick project.</whine>

-rb

* EDIT: I often use a modified "Rob DiStefano grip" - pinky extended, omit maniacal grin.
(EDIT 2: On closer inspection, I see he's holding a rotary tool. But the grip is the same.)