How old is my Triplett 310?

[BeBuLamar]

I just bought this Triplett 310 VOM today at an estate sales for $7.50. It's full functioning and reasonably accurate. It reads a bit low on both AC and DC voltages. I wonder if there is a pot for calibration? Also how old is it? I know the first one was made in 1955 and they still make them today.

[coppercone2]

well I got one of those from the 80's but I destroyed the acrylic knob. I have been meaning to polish out a groove in there so I can glue on something, or to find a replacement.

Check for leakage from the 12V battery in there for Ohmmeter mode.

And its adjusted by replacing resistors IIRC. That thing is pretty stable and small, I don't think I saw any trimmers in mine (but its for Bell)

Yours has a knob on the bottom, mine has more of a watch dial.

I think I have a 318 though. Maybe you can just get parts for that still, I never looked. I had a fun time polishing it with tooth paste lol


It has a potentiometer for ohms, but I don't think you can do anything with the voltage dividers other then replacing resistors


https://www.parts-express.com/pedocs/manuals/391-040-triplett-310-manual.pdf

[coromonadalix]

your needle mechanical zero  seems wrong for a start

and if this attached file     schematic / brochure is right you  have only 1  trimpot in it ....

and it has an 1977  stamp  on it   it give some insight ...

[Shock]

By the look of it 70s or early 80s is about right.

Edit:
If they didn't update the model at all looking inside will give you a rough date code if you can find a dated component or age them. Don't always jump straight to calibration to fix things. If it has a sticky or problematic movement, non zeroed or a drifted component, you will have just wasted your time and possibly made it harder to pinpoint.

[schmitt trigger]

Does it read low on ALL of the AC and DC ranges?

If so…I would like to think that then it is possible that the movement itself has a flaw.

Keep us posted on what you find.

[coromonadalix]

could be... you have to remove the clear windows, and see with some slight air towards it, if the needle move freely   

dont touch it with hands


the variable resistor is in the ohms section,  should be the zeroing ... ohms compensation   

and maybe some deoxit cleaner ...

[Stray Electron]

well I got one of those from the 80's but I destroyed the acrylic knob. I have been meaning to polish out a groove in there so I can glue on something, or to find a replacement.

  I THINK that this is the same meter that I was issued in May 1977 when I went to work as a Field Engineer for Burroughs Corporation.  IBM issued a very similar (or the same) meter to their engineers except that it was marked IBM on the front instead of Triplett. But I suspect that it was made for IBM by Triplett.  SOMEWHERE I still have one of the IBM marked meters.  I picked up that meter in the early 1980s and I liked the case it was in so I used the case for something else (I don't remember what) and I shoved the meter into a corner somewhere and I have no idea where it is now.

  Those meters used to plentiful around garage sales, flea markets, Ebay, surplus stores and ham fests.  Look on Ebay for a parts unit.

[BeBuLamar]

Actually it's not that bad. I checked the 3V and 12V range and to have the meter needle at 3V I need 3.082V and to have the needle at 12V I need 12.34. So it's about 3% low but that is considered in specs. For the 60V range as I don't have a power supply that can go 60V I make the needle point at 50V and I need 49.50V which is better.

[coromonadalix]

normally on the needle enclosure backplate, you're supposed to have the error %  writen on it ... normally in the 2 to 2.5%  if i recall  ...

you may never get better results than that

[Poroit]

I think you have done well for $7.50.

I checked the manual and DC Volts, Ohms, DC mA are listed at +/- 3%, AC Volts +/- 4%.

Do you reading change slightly if you lightly tap the case with your finger?

The pivots in these meters can get flattened over time due to getting bounced around in Tool boxes.

[BeBuLamar]

The meter movement appears to be quite good. I see no sticking and the readings are consistent.

[BeBuLamar]

Doing some internet search I found that mine is of type 1 which is the oldest. Triplett started making the 310 since 1955 but since my type 1 isn't the oldest of type 1 because the range selector has a screw. So I guess it's around 60 or 70? Anyone know when Triplett made the type 2?