I purchased a Triplett 630 na on eBay that has a problem with its needle swinging even with the
most gentle movement. When you handle the meter the needle swings back and forth and takes a while
to settle down. Any suggestion on what is causing the needle to swing so freely? Can it be be
adjusted? Appreciate any help.

Does the meter work otherwise? Check dampening in Amps function. Or try with a short jumper across the movement.

If the meter is "un-damped" when in amps function, the movement may be open or, a broken wire between movement and shunt. If the meter moves, un-damped, with a short across the movement terminals, the meter movement is probably open.

Good luck,

Charlie

Some of the older 630-** series (Type 1's) came with an intrinsically low damped movement, where the needle will swing/oscillate like a fast pendulum even when the movement is perfectly good; these meters were made that way. I'm pretty sure that later Type 1's have a higher damping factor in the movement; then somewhere in the 630-NA Type 2 production, they started using Taut-band/Suspension movement, which are much more damped even with the movement open (not shorted across or in any Amps range) which is a function of the phosphor-bronze taut/torsion band, it's length, cross-sectional area and tautness. All of the 630 series (I think) have a "OFF" range position (Up), where the switch shorts out the movement to provide maximum damping for storage or transport/shipping. Over the years, I've received more than one 630-NA and recently a 630-M (1ua fs mvt) where the two brass machine nuts were loose enough to the meter where the switch in OFF didn't work to dampen the needle. Another major culprit on all (full-size) Triplett VOM's can be the small mv trim adjuster, which may form corrosion; clean or replace it before calibrating. Also, some of the earliest Type 1's have a series mv hand-ww resistor inside the mvt case (where there's no external trim mv adj), which craps out with age as the acidic beeswax eventually corrodes the wire; the symptom is a dead movement with wildly swinging needle, but often it's just the mv trim resistors. This also applies to most Simpson 260 series, but their "OFF" range position is usually labelled "Transit". Most Triplett 310's do not have a mv trimmer; instead they have a "selected" 1 percent resistor shown on the parts list.

Hello Fred & Charlie,,

Thank you for all of your great advise and troubleshooting info for my Triplett 630 NS that I purchased on Ebay.
I placed a jumper wire across the meter terminals and the needle still swings very bad. I guess that I got ripped
off just like many others that shop on Ebay. It a shame, the case and plastic meter face in in pretty good shape
and 99 percent of the parts are there. If anyone needs spare parts let me know.

Again, thanks for your help.

I have a Triplett 630 NA parts unit that has a bad meter. The case and meter face look nice and there are lots of good spare parts inside.
If anyone is interested send me a PM with you personal email address and I will send you a set of detailed pictures of it.

Yes, the 'bay is certainly a crapshoot with test equipment. I also recently got ripped on a TTT630-NS Type 2 from Ebay where the seller was a gift/curio shop in the Midwest; the tester looked like new, not a single scratch anywhere, but they added a photo where someone had fiddled with a battery holder and snipped off one wire, so I knew I was taking a chance. Their caveat said something like as-is/unable to test, but should be able to fix. I paid a total of $34 and found the mvt armature was blown, so later I may transplant a good NS (5ua) mvt from another one (having cracked case & bad rotary switches) into it to make a working tester. Of course, though, for $34 I didn't complain, I knew it was a gamble.

BTW, do you realize you started your thread on a Triplett 630-NA (50ua/20K Ohms per volt DC), and ended it with your model NS? They are completely different testers. The NS' mvt is 10 times as sensitive as the NA. Did you confirm that the movement armature is blown, as some of the earlier VOM's have the mv calibration resistor tucked inside the meter housing which can blow out & easily be replaced. Easiest way to open the housing is to remove clear acrylic window, then remove number scale. Also, some of the pivot/jewel, and some early tautband/suspension movements will still oscillate rapidly like a pendulum even when the movement is good; so if its back-to-back meter protection diodes are damaged/shorted, they won't allow any current to the movement & the needle will just swing uncontrolled; so if your tester has these installed, remove them and re-test. A large overcurrent can zap these protection diodes; they can fail either open or shorted/crowbar'd.

I am sorry I made a typo. It is definitely a NA and not a NS. I shorted out the meter with a jumper wire and it still just swings back and forth. In the meantime I contacted the seller and he agreed to give me a refund minus the cost of return shipping which is nice. Thanks for your help.

I have a Weston a.c. ammeter, with two ranges, that I calibrated using a Fluke 5700A. I had the % errors noted on a label for correction.

It was never used after cal. I went to use it the other day and it was completely dead. Comes apart strangely and I didn't have time to delve deeper.

I hate it when they die on the shelf like that.

Charlie

Recently I took up a new job at a meter shop. I know we have a bunch of spare meters in our bone yard for the 630 series. Will check Monday.

-John

[quote]I have a Triplett 630 NA parts unit that has a bad meter. The case and meter face look nice and there are lots of good spare parts inside.
If anyone is interested send me a PM with you personal email address and I will send you a set of detailed pictures of it.

[/quote]

I [i]think [/i]I sent a PM but not having done that before, I'm not sure if I did it correctly. I have a 630 NA that is cosmetically not that good and am interested in your parts unit if you still have it.

Thanks!
Barry - N4BUQ