Mr Carson’s SMD capacitor Twist-off Method

[@rt]

Hi Guys
Mr Carson’s video, somewhat dated now, caused some fury in retro computer groups.
Basically, if the board was cheap, or the caps were already leaky, this is dangerous.

But I think he copped it way too much. The video demonstrates with a Tectonics PCB.
Retro enthusiasts appear to think their Commodore PCB is the same quality.

This is probably the first time I’ve ever thought of a topic I’d like Dave to do.
Differences between PCBs today, and also all through the 80s to today.


Mr Carson’s Lab (Original Video)

[KE5FX]

Not much point in that.  Soldering irons are $3 each at Radio Shack eBay.  Buy two.

[@rt]

Have you tried removing an SMD cap with an iron?
Yes some of the cheaper tweezers are effectively a pair of soldering irons,
but have you tried removing an SMD cap with two soldering irons then?

I’m not endorsing it.
What you need is a blower that might cost about $100 for a cheap China unit, and perhaps an iron to install the new ones.

[james_s]

I've re-capped dozens of devices, Tek scopes, 68k Macs, Game Gears, etc. The twist-off method really is the best way I've found to remove them, of all the methods I've used, it's the only one that I've *never* damaged a PCB doing. The key is you have to push down and twist. The guys freaking out about it have never tried it, simple as that.

Desoldering is iffy even with two irons, the leaked electrolyte affects the solder and prevents it from melting and flowing easily, also these are often on dense boards where you can't easily get to both sides without melting adjacent parts.

[@rt]

I could make a video doing the same with a Commodore board from 1993, and it will lift traces.
A serious one I mean, not exaggerated like this was just to prove a point.

Like I said in the Amiga group, Commodore PCB copper is stuck to the substrate with a mixture of flour and water,
and the solder mask is made from hemp from the side of the road in India.
It’s the Commodore boys who got upset about it.. thinking the whole World is about Commodore PCBs,
and ripping into Mr Carson, for what is really not so bad.

Personally, I blow them off, which can also pop them, and also cause leaked electrolyte jus the same.

[james_s]

I re-capped a few Amigas using the twist off method and it worked just fine. If you had problems you weren't doing it right.

[@rt]

I’ve never twisted off a cap full stop.
But I have had Amigas come to me with loose capacitors floating inside
them because whatever was holding them down was eaten by the capacitor’s own spew.
I’ve also had a CD32 FMV module with a cap lifted off at one end for no apparent reason.

[james_s]

Yes, the leaked electrolyte is quite corrosive and makes a big mess, especially when not caught in time. Even so, heat is far more prone to causing the pads to lift than a gentle mechanical twist combined with downward force, that provides no lifting/tearing force, it is all lateral and shears the fragile pins right at the body of the capacitor.

[TheSteve]

Pretty sure Paul was only recommending the twist method for the wet SMT tantalum capacitors, not the dry ones as shown in the destructive video above.

[james_s]

The twist off method is for SMT electrolytic capacitors *only*, not tantalum. The cylindrical electrolytics have thin wire leads that pass through a plastic base to pads that solder to the PCB. It's these thin wire leads that easily shear off when you twist it.

Tantalum chip capacitors rarely need to be replaced anyway.

[rs20]

This is probably the first time I’ve ever thought of a topic I’d like Dave to do.
Differences between PCBs today, and also all through the 80s to today.

That would you want him to actually do? It's pretty hard to answer questions of "safety" like this in any way other than trying it -- but that can only give one of two answers: "I broke some boards, this seems dangerous" or "I didn't break anything, so it's safe with these particular boards and and PCB types, but YMMV." But Mr Carson seems to have done that already? Very hard to come up with anything legitimately authoritative.

[@rt]

For Dave I was talking about changes in PCB substrate, quality of manufacture, etc, over time, and differences in quality between boards now.
Nothing to do with repair.

The reason I was breaking off any old component is to show that for a quality PCB, it’s pretty hard to lift traces.
This would not work on a Commodore board of the same era (early 90’s).
Yes, I understand the “twist off”  process, and have done it on similar junk boards, that were never going to be repaired.