http://i956.photobucket.com/albums/ae46 ... 373002.jpg
http://i956.photobucket.com/albums/ae46 ... 373001.jpg

This Simpson 373 has a sluggish meter movement. After pulling the meter I don’t see any noticeable obstructions. The magnet seems strong. What would be the best way to troubleshoot. The meter needle does move across the dial with light finger pressure.

Thanks,
Scott

First, make sure the needed isn't rubbing on the plastic face of the meter case! many meters end up doing that from a slightly bent needle that clears a portion of the face but not all of it to move freely left to right and back. Sounds silly but it happens often. If it isn't that then try my next suggestion below:

Moving the needle with your finger vs. current thru its own coil is quite different. I'd suspect improper tension at that adj. screw at the center of the movement. It's there to adjust play in the tiny pivot points of the needle itself. Too tight and it will be sluggish. Too loose and the needle will flop around. We are talking very small adjustments here - trial & error. Your meter's movement has is similar to the one pictured below-- notice the "set screw" at the very center.... that's the adjustment you need to check. Again, very small adjustments with a jeweler's screwdriver.... probably a very slight turn counterclockwise to start with.

It might be magnetic dust on the inside surface of the coil bobbin, or whiskers
growing out from the center pole piece. That Simpson is a very nice meter.

Here is the part Mars didn't explain: (Circa ARF 2010)

You need a lesson from the Mark Palmer School of D'Arsonval Meter Movement Repair:

1. Disconnect meter from circuit and remove from equipment.
2. Open meter case. If sealed, pry open with old screwdriver.
3. Stare at meter movement for several minutes and ponder.
4. Flick meter needle a few times with finger.
5. Poke meter spring with small screwdriver.
6. Loosen meter jewel bearings, and re-tighten.
7. Blow in to meter magnets and coils.
8. Hook up meter to test.
9. Discover meter now works 100 times worse than it was before.
10. Toss meter in trash.


-Mark-

Here's the last step Mark Palmer didn't include:

11. Go drink a beer.

Sounds all too familiar. I recently bought a Simpson 260 Series 6 multimeter. Its meter movement would stick just a bit at full scale.

I performed steps 1 through 4 (maybe 5?), skipped step 6 and went directly to step 7 and step 8. Step 9 differed in that the meter worked perfectly so I skipped step 10 and put it back the case.

Maybe next time I'll follow the instructions properly...

Barry - N4BUQ

Thanks for the answers……well most of them. Mars you had it right on the center screw adjustment.
Backed that off slightly and the needle moved freely. After some testing on a measured circuit it is accurate to just past the half scale on the meter and then the needle stutters and/or vibrates. I suppose that is the fine line of adjusting that was mentioned.
Also Steve mentioned magnetic dust/whiskers potentially causing problems. If that was interfering, is there any way to remove?
Time for a break,……number 11.

You can usually see if there are any particles between the coil and either magent or the center pole piece with a jewlers loup. I have used a wooden tooth pick to very carefully remove them.

The above should be done before you have any beer

If you do take your Simpson 373 (or any other in their school-lab 37* series), be sure to not lose any of its screws or other hardware. There are all sorts of weird sizes hardware in there, like 4-36 solid brass and stainless steel screws that no hardware or industrial supplier may have in stock. Simpson, like Triplett & Weston just maybe (??) used to hand out salary merit raises to their engineers for specifying a previously unknown screw size, just to drive repair shop technicians and hobbyists nuts. For that reason alone, I keep plenty of the broken Simpson 370's to have enough spare hardware to complete a repair when those microscopic-size screws go zinging cross the room when my stainless-steel tweezer goes 1/2 mm off course. After these late-nite episodes, I see where the Mark Palmer School of meter repair has merits.

Thanks David and Fred.......good advice. The meter is working fairly good now after a number of fine adjustments. Still have a bit of sticking/stuttering in upper part of meter scale. Can't seem to adjust the center screw to the point where the needle is stable and not too loose and eliminate the upper scale issue. Good accuracy otherwise.

Just one thing to mention, if you decide to adjust the meter jewels. In the Simpson movements, you'll have to loosen the locknut around the jewel before adjusting it, and make sure to keep the jewel from turning while you tighten it again. You'll want to adjust the jewels so that the pointer has just a little bit of bounce when you tap the meter. Not Sure if the 370 has the later Simpson spring backed jewels, so be careful when adjusting.

I have a bunch of the 379 Battery Testers, and they're fantastic. Just wish there were more parts available for them still.

Fred, I forgot to tell you, thanks a bunch for the documents on the Triplett 630-PLK circuit. I got mine working again. Looks great with it's translucent case back.
Now if I can just find some parts for my Dupont 101 Blaster's Multimeter...

-John