Test Leads

[john_g]

Hi All

Not trying to teach anyone here how to ‘suck eggs’, but this may key in with a comment on another thread about advising soldering components together to get best performance.

Recently I was getting different test results for the same circuit, under the same conditions. This was driving me mad as I couldn’t understand why the results were different. The problem was caused by the test leads. The poor construction of the crimp connecting the lead to the alligator clip caused an intermittent connection; over 25% of my leads had this fault when tested for resistance. The solution, solder the lead to the clip.

Pic of poor crimp:

http://www.keepandshare.com/doc/2634...5-pm-586k?da=y


Regards

John

[minoly]

Thanks for creating this thread and sharing that example.
I agree. In addition - this is the elephant in the room some would rather not talk about or admit. I know, even as recent as a year ago, I might not have admitted it myself.

I have even had solders on the alligator clip, the bus, and on the transistor leads that became loose. (not all at once – from time to time over the years)
The problem was the cheep %$$ soldering iron I was using was not always getting hot enough to heat the surface sufficiently to create a nice solid weld. – “Cold Solder”
A brief moment of poor connection is enough to blow or ruin a transistor unknowingly even!

It can cause just enough damage to the transistor where it still spins the motor or gives the appearance to be working, but no longer turns on or shuts down hard enough to allow for the events we seek.

In addition, clip leads themselves can cause poorer performance. We want the most amount of surface area as possible for contact to lower the impedance in the system, and alligator clips have those nice grippy “teeth” that only allow for tiny areas of connection. I’m still a huge offender of this one.

Patrick