probe slip

fredag den 29. marts 2019 kl. 21.18.32 UTC+1 skrev John Larkin:

I have something like this

they are like needles and replaceable, sharp enough to stab through wire insulation

Tek used to make a line of probe accessories called 'SureToe' or something like that. They show up on eBay fairly regularly, for some fairly grossly inflated price.

You cold do something equivalent with a small glob of JBweld putty and saran wrap.

Cheers

Phil Hobbs

I use a sharp-tipped pogo pin (spring-loaded ATE test pin) set into an acrylic rod for those situations. They're superb. The springiness really, really helps.

Mine look kinda like this

I've got a bag of 'em from a flea market somewhere, heavens knows where.

Cheers, James Arthur

$62 for a set of two from Amazon, but not insulated near the tips. Maybe some shrink tubing would help.

Sewing needles are great, but the material is INSANELY hard to solder to.

Jon

I use sewing machine needles for this and they work really well. Don't even need an insulating sleeve as they never slip. The broad shank towards the top of the machine needles have is ideal for soldering your probe lead to.

I start with the female power connector that plugs onto a IDE hard drive. Sorry, forgot the name of it. Solder on a short piece of piano wire. Put some heat shrink on it. Fits over the existing DVM probe tip nicely.

After reading this thread, I think I'll use a sewing needle and spot weld it to the connector socket next time.

I'd vote for the sewing needle, painted with epoxy. Having used lots in bed of nails testing they're pretty good, though they do fail to make electrical connection now & then.

I'm not suggesting it, but would a propelling pencil lead be usable somehow? If it slips, its R limits current flow.

NT

How about these? Perhaps a bit large for your application, but have a very, very sharp tip...we usually sell them with Bob Parker's Blue ESR kit:

John :-#)#

The pogo test pins are even better -- nearly as sharp as needles, plus the spring-loaded compliance allows for hands moving slightly while probing.

I've been meaning to make real probes with them some day... I've had two mounted in short sections of plastic rod, and clip to them. The pin sticks securely into the solder, and the spring absorbs any hand-wiggle. They're really great.

Maybe I'll dig through the dungeon and see if I can find John some.

Cheers, James Arthur

I ordered some for the shop techs a few months back. I struck gold when I stumbled on the Google Search terms that included "iPhone repair". Maybe on Monday I can find and post the link.

Inexpensive, teeny-tiny, strong(-ish), and needle-sharp. with Fluke type test leads. Actually, very well made for the money.

John Larkin wrote in news: snipped-for-privacy@4ax.com:

Most regular scop probes have pull off grasping clips exposing a sharp probe tip.

That is the standard, John. Have you been out of the loop for the last 25 years?

There are also sleeved prick type probes out there too.

Lasse Langwadt Christensen wrote in news: snipped-for-privacy@googlegroups.com:

Fluke always has been the sharpest, hardest probe tips and material.

I think he wants slevved and even smaller than that. But just as sharp.

John Larkin wrote in news: snipped-for-privacy@4ax.com:

You can also get tiny teflon tubes. we used them on transformer input leads all the time. That way, they are removeable.

Jon Elson wrote in news: snipped-for-privacy@giganews.com:

Even the ones with the Gold electroplated tops?

On Mar 29, 2019, Jon Elson wrote (in article):

enough.

watery fluid that comes in a small bottle. Available in hardware stores.

What also probably works is the flux for soft-soldering stainless steel. Again, a watery fluid that one applies with an acid brush. Often found in plumbing supply stores.

Procedure. Clean sewing needle. Hold in a vice. Spread and scrub acid flux on area to be soldered. Using a hot (750F) soldering iron, tin the end of the needle. Allow to cool, was flux residue off with hot water. Then, solder wire to tinned area of needle using rosin-core radio solder.

Joe Gwinn

Yes, I want something that can't short pins on tiny leaded parts. It's tough to stay on a pin and look up at, maybe adjust, a DVM or an oscilloscope. Scoping two pins at once is exponentially harder. There are never enough official test points on a PCB.

Lately we are using unmasked ENIG vias, which are probe-able and reduce slipping, given a really tiny probe. That helps when you get lucky and have a via on the interesting signal. You can solder to them too, for extended probing.

I bet a really small sewing needle would stick in one of those vias, with something like a 12 mil drill.

A robotic pantograph fet probe with a really good camera would be fun.

Some are titanium! Can you solder to that?

Some might be chrome plated brass or something. Dremel the chrome off maybe.

Not nearly sharp enough, but still fat enough to short pins on a TSSOP or US8 package.

I've been learning for 50 years. And the parts keep getting smaller. Working under a 6X Mantis with a new Tek or Rigol or LeCroy probe (we have all of those) is still a challenge.

A LeCroy fet probe lists for $6K.