After reading the wonderful thread about the Simpson 260, I thought that it might be reasonable to give a little "equal time" to another brand that has been around for over 100 years...Triplett.

Three popular models of Triplett VOMs that are still available are shown in Pix 1&2...The three meters shown, Left to right in Pix 1 are 630-NA, 666-HH, and a 310. All three have the early "meter movement" Triplett logo on the scale (used into the 60s), the 666 also displays the "red dot", which I believe was dropped in the 50s. The 630 and 310 models still look much like the older models pictured, but the "modern" 666 model now has a recessed range switch, much like that on the 630. Pix 2 shows a side view, revealing the high degree of miniaturization involved in the design of the tiny 310 (4 1/4 x 2 3/4 x 1 5/16" and about 8 oz.). The 310 is my personal favorite VOM, and I have collected many variations.

Pix 3 shows 50+ years of model 310s. The 1955 310 (type 1, although not labeled as such) on the left displays the "meter movement" logo and the "red dot", the type 7 on the right, purchased in 2006, has the stylized "T triangle" logo. The later model also features an enclosed range switch, similar to that which was incorporated earlier in only the "premium" model, the 310C.

Pix 4 shows three different models that I have collected (although there are others). The model on the left is a 310C (type 3), which has a polarity switch on the left side, better AC sensitivity (15K ohms/volt rather than 5K) and an enclosed range switch. The center meter is a fairly rare 310 FET model also with a polarity switch as well as 10 meg ohm input resistance, DC voltage range down to 0.3 volts full scale, a "center zero" scale, ohm reading to 5000 meg-ohms and ma readings down to 0.12 ma...much like a solid state VTVM! On the right is a standard 310 (type 2) for comparison. All three display the red "Triple T" logo, used in the 70s and 80s.

Pix 5 shows packaging and labels used on the late (2006 or so) type 7 310 and 310C. Volt Ohm Meters in a "bubble pack"! :yuck: The 310 type 7 on the left proudly displays a "made in USA" logo. :thmbsp:

In Jan. 2007 Triplett was purchased by Jewell instruments in Manchester NH, and apparently the factory in Bluffton Ohio was closed. The latest models of 310 and 310C are type 8.

jr

Versatility of the type 310 meter could be enhanced by several accessories.

Pix 1 shows the Model 100 package, which contains a 310 meter (type 1 shown here) with manual and probes as well as the accessories that add "clamp on" AC amp reading capability to the meter. The important elements that are added to the 310 are the model 10 clamp on probe, which attaches to the top of the 310 meter body, the model 101 adapter for measurement of current through a standard wall outlet (2 prong only) and an extension, for using the clamp probe remotely from the 310 (not shown). A "genuine cowhide" carrying case for the system is included. The Model 100 package sold for $78 (1971 Allied catalog), compared to $44 for the standard 310, $56 for the 310C, and $74 for the 310FET, making it a decent bargain.

With the increased versatility came some confusion... To read the current correctly, the user had to select the 3VAC scale on the meter. This special scale was somewhat non-linear, due to the characteristics of rectifier diodes. The user then had to multiply as necessary to determine the correct value for the various ranges provided by the switch on the clamp on attachment (6 to 300 amps).
When the "type 3" 310 meter was introduced, the confusion was somewhat remedied, as more numbers were added below the 3VAC scale, to aid the user in simple multiplication. The designers also clearly marked the 3VAC range switch with the designation "AMPS", which caused another confusion... everybody knows that one should not try to measure voltage with a VOM set to Amps, so does the 3VAC range still exist? :scratch2:
With the introduction of the "type 4" the confusion was remedied as well as possible (short of adding another switch position just for AC amp measurements)... the added numbers were left in place below the 3VAC scale but the switch position reverted to the earlier 3 VAC marking.
Pix 2, left to right, shows a "type 2" without the added numbers, a "type 3" with the additional numbers and the "AMPS" switch position and a "type 4" with the confusing switch nomenclature reverting to the original 3VAC designation. All three meters display the red "Triple T" logo, used in the 70s and 80s.

Pix 3 shows several types of model 10 attachment. Left to right, an early model for the 310, a model for the 310C (necessary because the "C" model had different AC sensitivity), both with a bakelite case, and a later model, with a plastic case, and a 2 wire connector, so that the probe could be used (somewhat) remotely from the 310 (or 310C, in this example) without the need for an extension cord.

Provisions for attachment/connection of the type 10 probe changed over the years, as shown in Pix 4. The early 310 (type 1, with red dot) shown on the right, did not have the attachment point for the type 10 probe. It does, however, have the ground plug... more on that later. The later "type 1" in the center of the picture, has the attachment point added. The "type 7" on the left no longer has the ground connection (only a blank hole), necessitating the use of the later 2 wire probe attachment, similar to the one shown in Pix 3.

jr

Over the 55+ years of production of the Triplett 310, the probe design changed considerably. Probes grew in length and girth, I suspect largely in response to changing safety regulations. A finger-guard was added as well as provision for attaching alligator clips to the probe tips. Pix 1, right to left, shows the progression of probe designs. I can't imagine holding the tiny probes on the right to measure 1200 VAC, the highest full scale reading available on the standard 310.:eek:

To accommodate the larger probes and added alligator clips, unfortunately the carrying case for the 310s had to grow to larger, fatter designs. Pix 2.

I mentioned in an earlier post that even though the very early 310s did not have a provision for attaching the clamp-on Amp meter probe, the ground receptacle on the top of the meter case served a useful function. The design of the early probe set allowed the negative probe tip to be unplugged from the probe body as shown in Pix 3.

The banana plug from the probe tip could then be plugged into the receptacle on the meter to provide a convenient method of probing a chassis. Pix 4.

jr

I have a Simpson 260 and a Triplett 630-NS. I prefer the 630. A nice thing about the -NS version is it is 100k/volt, so it doesn't load things down. I just like the feel of the 630 better than the 260. It was given to me about 30 years ago, and I suspect I'll use it for another 30 or 40.

This 1958 ad shows a number of Triplett VOMs... What a line-up! :thmbsp:

My 1971 Allied catalog lists the following 630 models:

630......Standard Bakelite 2% 20K ohms/VDC .............$64
630A.....Bakelite 1-1/2% 20K ohms/VDC.....................$75
630PL....Plastic meter face 2% 20K ohms/VDC.............$64
630PLK..Similar to above, with transistor "fuse"............$98
630APL..Similar to 630PL, 1-1/2% mirror scale.............$75
630NA...Similar to 630APL, but with "gearshift switch"...$98
630NS...Similar to above, but 200K ohms/VDC............$116
630M....Similar to above, but 1meg ohms/VDC............$231
631......VOM/VTVM 11 megohm DC input resistance.......$86

Also:
666R....Small Handheld 5K ohms/VDC..........................$46
310......Compact handheld 20K/5K ohms/Volt AC/DC.......$44
310C....Compact handheld 20K/15K ohms/Volt AC/DC.....$56
310FET..Compact handheld 10 megohm DC input ...........$74

Lots of fine (too many?) models to choose from.:scratch2:

jr

Geoff Bourquin: That 630NS sounds like a fine meter!:thmbsp: I have never used a Simpson 260 but enjoyed using a 269 (with 7" mirrored scale) many years ago.

In my attempt to collect the various Triplett 310 models, I have encountered a few custom models, built for other companies, and perhaps an engineering special.

Pix 1 shows a 310 type 3 that appears to totally standard except for the "Simplex" logo on the meter face.

Pix 2 shows a highly modified model 310C type 2 made for IBM. It does not have clamp-on amp probe attachment point on the top of the meter case, and the DC voltage range is modified for a much lower range (0.6 to 60V only). Note that the usual 600v AC & DC receptacles on the meter face are labeled 30VDC and 60VDC.

Pix 3 shows a curious model labeled "310-x"... it appears to be a totally standard 310 type 1 except for the labeling of the lowest amp range on the range switch... "0.6" replaces the normal ".6" as the designation for the range. While "0.6" might be more mathematically correct than ".6", it appears less aesthetically pleasing IMHO, on the range switch.*

If anybody has other "special" 310s please post 'em up here!

*up-date : I looked at the meter again, and concluded that the designation on the switch might actually mean ".06" rather than "0.6"... tested the meter and it appears that is indeed the case, the range is 60 micro-amps full scale !...Perhaps a special for a customer requiring a very low current DC range, for some reason. Xerox perhaps?

jr

Today, I received an eBay win of a model that I have not collected before, the 310 TEL. (Pix 1) The 310 TEL appears to be a current model, as it is listed on the Triplett/Jewell website*.
The 310 TEL is a 20k/5k ohms per volt DC/AC like the standard 310 model but has a polarity reverse switch, normally seen on only the 310C. In addition, the Higher voltage receptacles (normally 600 or 1200v) have been plugged, so the highest range is only 300v AC or DC. While it retains the attachment point for the Amp-Clamp probe, the extra meter scales have been eliminated. I am assuming that this is a "stripped down" model aimed at the telephone industry. The label on the back tells a sad story (Pix 2).

*link to website (not affiliated)
http://www.triplett.com/product_info.php?cPath=29&products_id=101
jr

I have a Model 10 amp probe that was an accessory for my 310 which I had back in the 1960's and no longer have. two questions..... will the model 10 amp probe fit the new 310's and 2nd question where is the best place to look for an older model 310?
thanks for your help..........clark

I have a Model 10 amp probe that was an accessory for my 310 which I had back in the 1960's and no longer have. two questions..... will the model 10 amp probe fit the new 310's and 2nd question where is the best place to look for an older model 310?
thanks for your help..........clark

Hi Clark! Welcome to the forum!

In general the older amp probes will mount ok on the newer meters, BUT the newer meters do not have the jack on the top surface to make ground connection, just a locating hole. Take a close look at post 2 in this thread... the new amp probes use a 2 wire plug to make both connections to the jacks on the face of the meter. Seems like it would be fairly easy to add a second wire to the older style amp probe, if necessary.
In my collection, most were purchased off of eBay, over the last 2-3 years.
Good Hunting!
jr

Wow amazing wright up! I have a 625-NA that looks like it fell down a flight of stairs. The Bakelite case is all broken with a few chunks missing and all 3 plugs are broken. The meter works perfect though. It looks like a Simpson. Same basic shape/black case.

I always liked the Simpson 260 even though the Triplett 630 was clearly superior.

I do have a 630-NA with a serious problem. The pointer will not sit on zero or full scale. Other locations are fine. For a long time I thought it was a static electricity issue but now I lean more toward thinking it's a bad movement. I had a 630 I gave to a friend which actually is almost dead on accurate, unlike the 630-NA. I don't know what to do about this, as the meter is basically terrific. I love the 1/2 ranges, the accuracy specs, and the available ranges.

I modified my unit because obtaining the 30 V battery was getting to be a problem. I made a little supply from a wall wart I had laying around and mounted an almost invisible power jack on the meter case. Works great and will never need another 30 V battery. Info and pics can be made available to anyone interested.

I can see that you can still get the 30v batt, but are they new?

I have a 630 that I picked up at a swap meet, corroded batt connections and fuse holder, but other than that in perfect shape.

I'm not sure how I missed this thread. jr_tech, you really gave a nice history!

I should try to find an old Simpson or Triplett. Even some solid state HiFi equipment I have from the 80's specify the use of a 20Kohm/VDC meter for adjustments. Using a modern DVM doesn't always work since the voltages the manual gave for adjustment assumed the 20Kohm/V loading.

John

Thanks for the comments!

I have obtained special batteries from these people... they appear to be new and fresh... but very expensive:

http://www.batterymart.com/c-industrial-batteries.html?utm_source=Bing&utm_medium=CPC&utm_term=eveready_504_battery

Most of the time, I "fake it" using cheap 12V smoke alarm batteries, such as the Energizer A-23 , or stacks of watch batteries. Sometimes I just "go without" as most ranges (except the highest ohm) will function fine without the expensive battery.

Not affiliated with the battery vendor,
jr

I always liked the Simpson 260 even though the Triplett 630 was clearly superior.

I do have a 630-NA with a serious problem. The pointer will not sit on zero or full scale. Other locations are fine. For a long time I thought it was a static electricity issue but now I lean more toward thinking it's a bad movement.

I just did a little experiment with my 630... for sure, I can get some erratic behavior by charging the meter face, but it is pretty easy to discharge with a slightly damp cloth... my guess is that your meter movement has a problem. I have not seen that particular problem before.:scratch2:

jr

I wonder if this is a taut band or pivot suspension. The meter is still usable as long as I stay away from the ends of the scale.

I wonder if this is a taut band or pivot suspension. The meter is still usable as long as I stay away from the ends of the scale.

My 630-NA appears to be a taut band...I can clearly see a u shaped spring that tensions a support wire that passes through hole in a white center insulator. Are the little white travel limit "bumpers" on yours possibly interfering with the needle travel?

jr

The needle travel isn't restricted. If it's on zero, I can tap the front and it will gently swing over to the stop. If it's at full scale for a moment, it will start to drift up to the top stop. If I reduce the meter current, the needle starts down and overshoots the full scale mark. It just won't stay on full scale or on zero. Well, it will stay on zero more often than not but I have to tap the meter sometimes for it to do that. When I tap it, it moves smoothly. Better than tapping is to move the entire meter so the pointer's inertia moves it.

I still have a small quantity of small pocket VOM's still NOS in the original unopened mil-spec box that the military bought back in 1989. Battery supplied with it is no good (packed separately-no damage) but still a good little meter. Whoever the original OEM was, sold them in the past under many different names. Anyone remember these?

Triplett 310 type 3....
I am trying to find a source that has the fuse for this type 3. Have tried:
Radio Shack, auto stores, various electronic outlets, Triplett etc. without
luck. I have a total of 7 310's, 2 are disabled because of this missing fuse.
the fuse is:
1/8 amp 8AG,MKB or equivalent
of course the ohms positions won't work because of this missing fuse. All
other ranges work fine.

Does anybody know where I can get these fuses. Even the location of
this fuse is different than what is shown in the 310 manual. Both of
mine that need the fuse have the fuse located UNDER the 1.5v battery
not in the "out in the open" location shown in the 310 manual.

OLJOE

OLJOE, I got 'em. 8AG @ 1/8 amp in NOS Littelfuse pkg of 5. How many do you want? Julian

julianb@charter.net

Had an inquiry about battery substitute for the 7 volt battery used in the FET 310 model. Mine came with, and seems to be working nicely with a 6 volt lithium battery, K28L. The 310 contacts were bent slightly and a foam spacer was added to assure a tight fit. The 1.5 volt cell is a fairly common typr N.

Here is the schematic and parts layout and parts list:

https://live.staticflickr.com/65535/50226541287_0692f655ae_c_d.jpg


https://live.staticflickr.com/65535/50225676908_7934db0409_c_d.jpg

https://live.staticflickr.com/65535/50225674258_0afb1ab699_c_d.jpg

Hope this helps,

jr

Thank you, jr!:tresbon:

Thanks for a great introduction to a fine VOM Jr tech. My HS Vocational Tech School had these and the EICO 232 VTVMs for the shop benches. We were also schooled on how they loaded both transistor and tube circuits.

Before DMM's of course, the Triplett 630s were 9-10 years old then, yet there seemed to be very little evidence of wear or troubles. I will look for one at a swap meet!