Safely measuring SOIC with probes - Page 1
Forum section: electronics / beginners

author: rthorntn
author_rank: Frequent Contributor
timestamp: June 26, 2025, 02:04:35 am
content: Hi,Noob question, how do I safely and consistently probe pins on a SOIC16 without say accidentally shorting two pins?I have a eurorack NLC Cellular Automata module that I just built that's misbehaving so I want to scope the pins.Bonus question, I have a sysclk sla5032 logic analyzer and also a rigol ds1102 oscilloscope, whats the best tool for the job of confirming all the (12v?) ICs (tl072, bc847, 4070 & 4042) are working?Thanks!

author: coppercone2
author_rank: Super Contributor
timestamp: June 26, 2025, 02:48:35 am
content: the oscilloscope has a magic seemingly useless plastic piece of shit for dealing with thisLook at the top row of the picture. Its like a comb. 1.27mmyou might still have it in your? storage

author: rthorntn
author_rank: Frequent Contributor
timestamp: June 26, 2025, 03:08:16 am
content: Thanks, I'm 99% certain the Rigol didn't come with those, any idea if I can buy this now, maybe (if it's the only way) with a (not too expensive) new probe?

author: coppercone2
author_rank: Super Contributor
timestamp: June 26, 2025, 03:13:39 am
content: mine came with that they are yellowyou can find them somewhat or use another brand if you know the dimension of the probe tip. I don't think it would cost more then a few dollars.its called a IC tip insulator or somethingbut will it fithttps://siglentna.com/product/probe-accessory-kit-pak2/

author: jpanhalt
author_rank: Super Contributor
timestamp: June 26, 2025, 10:26:42 am
content: I use EZ-hook grabbers:(That is not my hand. I don't wear globs of nail polish.)For non-supply, I will often attach them while energized. For supply pins, you may decide to play Russian Roulette, or just unpower, and attach.

author: rthorntn
author_rank: Frequent Contributor
timestamp: June 26, 2025, 10:34:57 am
content: Thanks, the EZ-hook connects to your oscilloscope?

author: jpanhalt
author_rank: Super Contributor
timestamp: June 26, 2025, 10:58:40 am
content: Quote from: rthorntn on June 26, 2025, 10:34:57 amFor low frequency, I connect a short lead with pin that I grab with a conventional scope lead. I usually run my MCU at 16 MHz or 32 MHz (Tcy = 4 and 8 MHz, respectively) and can watch things like SPI, if needed. Mostly, I am looking at sensors that are fairly low frequency.

author: mtwieg
author_rank: Frequent Contributor
timestamp: June 26, 2025, 12:37:44 pm
content: Quote from: rthorntn on June 26, 2025, 10:34:57 amThese sorts of grabbers don't connect to the scope probe directly. Most often they have male pins,like this one(the pins are mostly recessed into the pastic body). You then connect your scope probe to that pin with a flexible lead. You can use ashort jumper lead like this, just jam the bare tip of the scope probe in one end. Some probes might come with their own accessories which make this a bit easier.Sometimes the grabber comes with a lead attached,like this one.It should go without saying that you should not reposition the grabbers unless the circuit is powered off, since you're likely to cause a short to adjacent pins in the process.Personally I don't use grabbers, as they can sometimes detach when slightly disturbed, causing disastrous results. Sort of like the screw driver in the demon core.When I need to probe something on a board and there's no existing strong attachment point, I will solder a short jumper wire to the pin/trace (one of those female jumper wires, so the end is insulated against accidental shorts).

author: jpanhalt
author_rank: Super Contributor
timestamp: June 26, 2025, 03:24:25 pm
content: Not all hookers are the same quality.I have found EZ-hook brand to be decent. There are other brands where the little hook on the end bends too much, or a user (me?) has abused it.I also use very flexible wire for the short connection. It used to be called "spaghetti" wire in the model aircraft crowd. It had lots of strands and a version of vinyl insulation that was soft and relatively thin.. Daburn* was one manufacturer. Today, you are probably stuck with silicone insulation. Anyway, when that connection is very flexible, I rarely, if ever, have a problem with the EZ-hook coming off an SOIC gull wing pin. I also keep a roll of blue 3M masking tape and run a strip across my probes to keep them stable.*https://www.daburn.com/2671UltraFlexibleSub-MiniatureWire-U/LSTYLE15681692.aspx The only probem is that distributors don't carry the whole line, and while ordering directly from Daburn is possible, if you want multiple colors it gets expensive.

author: MarkL
author_rank: Unknown
timestamp: June 26, 2025, 05:12:52 pm
content: You can get SOIC test clips which bring the pins out to posts with 0.1" spacing, which makes test connections easier to deal with. You can get a regular size sprung hook on it. For example, AP Products (now 3M) 923665-16:https://warwickts.com/851/923665-16-16-Pin-SOIC-Gold-ClipAnd Pomona 5252, which has a slightly different design:https://www.pomonaelectronics.com/products/test-clips/soic-clip-16-pinPlus plenty of knockoffs, if you search around.For a grabber directly on the SOIC pins, I personally like the Tektronix SMG50 (aka 206-0364-01):https://sigrok.org/wiki/File:Probes_tektronix.jpgThey have a strong spring, and the pincers are sharp and shaped so they don't easily pull off (photo below).A search for "tek test clips" will find them on ebay if you're ok with used (the part number is not printed on the grabber).

author: rthorntn
author_rank: Frequent Contributor
timestamp: June 28, 2025, 10:53:45 am
content: Thanks everyone!So on my Rigol I'm looking for the ~40usec 8V pulse that the high-pass creates from the 8V square-wave clock input, I can't see it by probing the output of the 100p.Can someone help me find this pulse, surely the Rigol should see a pulse that short, either I'm doing something wrong on the scope or the pulse isn't there and maybe there is a short somewhere around the comparator that I can't find?I see the clock go into the 100p but I see no pulses on the other side.This board is a nightmare that I'm about to give up on.