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DIY: Updating Multi-meter Terminals

I was given an old Multimeter many years ago, a Simpson 464 (Series 3).


For a long time it just sat on my bench as I had a Fluke 115 and this was on my list of personal projects that I just did not have the time for. Being a stright A college student (I mention the grades to give an idea of the time commitment) and the influx in a varity of new and cool electronics brought in for repair, time was defenatly limited to those things!

Being the last weeks of the semester things have calmed down, and the first thing I did this morning when I woke up, was grabbed the old Simpson 464 and got to work.

So the issue with the Simson 464 is the terminals for the probes. If you know what these jacks are called, please comment as I have not yet been able to find out myself (Not from the manual, friends or professors). I searched and searched for the orginal probes for the unit with no luck. Even the Simpson 464s on Ebay were all sold without probes.

So say this is the case for you, you can't find the right probes, you want something with jacks more suited to what you are working with, this is a simple and easy modification you can make to any bench top multi-meter (Or portable).

before after


This article may seem specific to the Simpson 464, but as with the other articles on the Ninjku Network, everything is written to be a matter of the same princpals apply. So what is shown here, you can apply all of this (using your head of course!) to fit what you need to do.

This article is also not limited to bench top Multi-meters, all the principals will apply for either Digital or Analogue meters of the portable type.

You can even apply these principals to changing audio jacks on a device from one type to another!



Things you need:

1. Multi-meter
2. Soldering Iron
3. Plyers
4. Screw driver
5. Solder
6. Soldering wick 
7. Terminals of your choice (Good idea to measure the sizes, to see if you can find the same size -- if not, it's okay!)
8. (Varies case to case) Washers

Getting started, find the terminals you wish to use (if you have a general idea of the size, or if you just went and bought whatever you could find -- if not, continue reading).

Everything in my shop has bananna terminals, and bananna binding post terminals. So that is what I went with. 


With everything in hand, you first want to open your unit to see what you are working with.


Things you will want to observe, are how the jacks are held in place to know how to remove them and how you will mount the new ones. You also want to make note of the wiring, such as which wire goes where. A good idea to be safe is to have photographic documentation, so snap a picture that shows where everything goes. This is a good method to apply for when you are in a situation where you need to remove everything all at once, and have no wiring diagrams (or simply do not know how to read them).

Another possible way, is to disconnect and change only one jack at a time so you don't get lost, but you always have the photographic method.

While you are in the unit (As with anything you open, good habbit here!), now is the time to check any fuses to make sure none are blown, examine capacators for signs of leaks, examine other compoents for signs of burning, and give a good blowing out with compressed air of  your choice.

Your terminals will most likely be held into place like many push buttons, dials, jacks, ect. Threaded with a nut to secure the jack to the face of the device.


To remove these, you will take your plyers and grab hold of the nut the best you can, and loosen it enough to the point you can spin it free with your fingers. If you have plastic threads, you want to take it a bit slow so not to damage the threads.

In some cases you will need to use the plyers the entire way to remove the nut, it depends on the situation.



Once the nut has been removed from the thread, you will not be able to remove the jack until the wire is removed from the rear of the jack. So take your soldering wick, heat up your iron and desolder the wire. 

Now you will be able to push the jack out toward the front of the unit.

NOTE: With the jack removed, you can now measure it to identify what size you will need.

If visiting Digikey, Mouser or any other electronics parts supplier, you can refer to the avaiable data sheets, to find out what size of part you are purchacing to match.



Your next step, it will be a good idea to always compair the sizes of what you are working with, if you do not have the same size. Thinner jacks can be fit using washers, however too large will require boring out larger holes, and possibly making some irreversible mistakes.

So if you did not source the same size, or can not find the same size, or have a size that is smaller (As the case here), you can work out how you will fit it to the panel. 

As you can see, there is quite a difference in sizes. 



Do a test fit to see where you will need washers. The front portion of the new terminal is wider as you can see, to keep the jack from being pushed inside the unit, and the nut on the rear is to keep it from falling out or pulling out when you remove a cable. Secured from both sides.

In my test fit, you can see the hole is just a bit too large, and there is a chance the jack can be pushed inisde the unit.



Now the problem with too large of a hole, and the panel side of the jack not being large enough to cover the hole, is that you need some way of closing this gap. You can't simple add a washer and nut, as there are no threads on the front portion. You can find two nuts if the threads on your new jack are long enough and have it sticking out pretty far. Sit back and have a look. Using your head, taking some time to think about it, you can find a way that fits your situation.

Hot glue is one way that can be used, but I don't like the idea of that. So for me, what I did was find some thin nuts, and I actually used a bonding adhesive to attach a nut to the front, to create a wider "lip" that would allow the post to sit flush with the face, and not be pushed in.

I made sure to pick a size that would not cover the jack identifiers.





NOTE: Everything was removed prior to installing new jacks and soldering in place, to clean the face, and the front push buttons.

Once your jacks are secured into place, you can resolder your wires back into place, put the case back togeather, and you are done!



After cleaning the face plate and push buttons, I had attached everything loosely in place for the sake of the article. You will notice the 10A jack is no longer red in color but black.

Black should always be reserved for common and ground if your Multi-meter has both red and black terminals. I have removed this 10A jack and ordered another jack of the correct color (Red)

This is not a must, it is what I have done, and it's the standard of color coding jacks on Multi-meters, so it is always best to go with the standard.

Again this is not required, you can have them all blue or even pink if you wish. It is your equipment, do what YOU are comfortable with. It is only a suggestion, that may save you confusion, especially if you are new, and these articles are written for the new person in mind!

(A second photo will be placed here to show any updates, such as the 10A jack in Red)


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