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 Post subject: TRIPLETT 630-NA Type 3
PostPosted: Mar Sun 29, 2020 4:19 pm 
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Posts: 149
Location: Charlotte, NC 28205
Gents,

I ordered & replaced two charred [R-27 & 28] resistors. According to my calibrated Fluke 289, all the DC scale readings are still about 5% off. Could this be the result of [one] out-of-tolerance resistor ? Sorry, I don't have the manual; but a down version would be much appreciated !

Jack


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 Post subject: Re: TRIPLETT 630-NA Type 3
PostPosted: Mar Sun 29, 2020 4:23 pm 
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Location: Wayside, NJ Monmouth
http://bama.edebris.com/manuals/triplett/630/

Try this like, one of the files there may be able to help you.


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 Post subject: Re: TRIPLETT 630-NA Type 3
PostPosted: Mar Sun 29, 2020 5:20 pm 
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Jack Cureton wrote:
Sorry, I don't have the manual; but a down version would be much appreciated !

??? I posted the manual to my manual archive web site on March 16 and posted the link in your other thread on this VOM:
viewtopic.php?f=8&t=374178

There isn't a manual with any more detail than that one. I don't believe the factory calibration procedure is available anywhere. Here is the link for the 630-NA Type 3 manual, again:
https://www.byan-roper.org/steve/manual ... manual.pdf

So you replaced R27 and R28. Those are the shunts for the 1200 mA and 120 mA current ranges.

Are the DC current ranges off the same amount as the DC voltage ranges? Are the V•A/2 ranges off the same amount as the V•Ω•A ranges?

Have you verified the 60 µA full-scale reading for the meter - is that also 5% off? (That's the 0.12 mA range, with the range doubler in the V•A/2 position.) This is the first step in calibrating the 630-NA. The 60 µA range must be correct, otherwise all other ranges will be off.

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 Post subject: Re: TRIPLETT 630-NA Type 3
PostPosted: Mar Sun 29, 2020 7:30 pm 
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Joined: May Wed 15, 2019 10:50 am
Posts: 149
Location: Charlotte, NC 28205
60 micro-amps on the Fluke 289 reads 59 micro-amps on the Triplett

Jack


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 Post subject: Re: TRIPLETT 630-NA Type 3
PostPosted: Mar Sun 29, 2020 8:28 pm 
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Joined: May Wed 15, 2019 10:50 am
Posts: 149
Location: Charlotte, NC 28205
stevebyan wrote:
Jack Cureton wrote:
Sorry, I don't have the manual; but a down version would be much appreciated !

??? I posted the manual to my manual archive web site on March 16 and posted the link in your other thread on this VOM:
https://www.antiqueradios.com/forums/vi ... 8&t=374178

There isn't a manual with any more detail than that one. I don't believe the factory calibration procedure is available anywhere. Here is the link for the 630-NA Type 3 manual, again:
https://www.byan-roper.org/steve/manual ... manual.pdf

So you replaced R27 and R28. Those are the shunts for the 1200 mA and 120 mA current ranges.

Are the DC current ranges off the same amount as the DC voltage ranges? Are the V•A/2 ranges off the same amount as the V•Ω•A ranges?

Have you verified the 60 µA full-scale reading for the meter - is that also 5% off? (That's the 0.12 mA range, with the range doubler in the V•A/2 position.) This is the first step in calibrating the 630-NA. The 60 µA range must be correct, otherwise all other ranges will be off.

60 micro-amps on the Fluke 289 reads 59 micro-amps on the Triplett

Jack


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 Post subject: Re: TRIPLETT 630-NA Type 3
PostPosted: Mar Sun 29, 2020 9:29 pm 
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Joined: Jun Sat 09, 2007 8:14 am
Posts: 4137
Location: Florida
I don't believe the 630's have any cal pots. I have two in the 630 series, a 630 and a 630-A. Both movements are OK but the 630's multiplier resistors had all drifted high. The 630-A was still in spec at first but one day I found a couple of ranges dead. Two of the multiplier resistors had opened up while on the shelf.

I used 1%'ers to fix the 630-A, screened 5% carbon films for the 630. The 630 screening used a successive approach that essentially calibrated each range individually.

RRM


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 Post subject: Re: TRIPLETT 630-NA Type 3
PostPosted: Mar Tue 31, 2020 1:11 am 
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Posts: 797
Some 630NAs have a pot soldered on the back of the meter movement, some have a custom wire-wound resistor there. In either case, it should be adjusted so that the .6v DC voltage reads correctly. In the original 630-NAs, a custom wire wound resistor was inside the meter movement enclosure.


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 Post subject: Re: TRIPLETT 630-NA Type 3
PostPosted: Mar Tue 31, 2020 1:57 pm 
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Jack Cureton wrote:
60 micro-amps on the Fluke 289 reads 59 micro-amps on the Triplett

Good.

What about the rest of the diagnostic info?
stevebyan wrote:
Are the DC current ranges off the same amount as the DC voltage ranges? Are the V•A/2 ranges off the same amount as the V•Ω•A ranges?


Alan S also has a good point about the meter needing to have the right resistance, so the 0.6 volt range is correct.

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 Post subject: Re: TRIPLETT 630-NA Type 3
PostPosted: Mar Tue 31, 2020 5:34 pm 
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Location: Charlotte, NC 28205
Alan S wrote:
Some 630NAs have a pot soldered on the back of the meter movement, some have a custom wire-wound resistor there. In either case, it should be adjusted so that the .6v DC voltage reads correctly. In the original 630-NAs, a custom wire wound resistor was inside the meter movement enclosure.

This 630 does have the mentioned potentiometer. Adjusting it [all the way to zero ohms] made an improvement but not enough. I disconnected the wire going to the wiper and attached it to the pot's case. Now readings I get in reference to the Fluke 289 are: Fluke; 0.6 VDC vs Triplett; 0.56........Fluke; 300VDC vs Triplett; 287.
So what resistor is slightly high in value ?

Jack


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 Post subject: Re: TRIPLETT 630-NA Type 3
PostPosted: Apr Wed 01, 2020 1:35 am 
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Joined: Mar Sat 03, 2007 12:53 am
Posts: 797
See if the meter movement slightly sticks by first applying a voltage that makes the meter go from 0 to 80% full scale, removing the voltage and applying a voltage that makes the meter go from 0 to 100% full scale and then immediately applying the first voltage which should make the meter go from 100% full scale to 80% full scale. If the meter doesn't go all the way back to 80%, then there the meter is sticking slightly which would make all the voltages read low.
If the meter is not sticking slightly, then there will be a wire wound resistor inside the meter housing which could be made smaller by paralleling it with another resistor.


Last edited by Alan S on Apr Wed 01, 2020 1:43 am, edited 1 time in total.

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 Post subject: Re: TRIPLETT 630-NA Type 3
PostPosted: Apr Wed 01, 2020 1:42 am 
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Joined: Mar Sat 03, 2007 12:53 am
Posts: 797
See if the meter movement slightly sticks by first applying a voltage that makes the meter go from 0 to 80% full scale, removing the voltage and applying a voltage that makes the meter go from 0 to 100% full scale and then immediately applying the first voltage which should make the meter go from 100% full scale to 80% full scale. If the meter doesn't go all the way back to 80%, then there the meter is sticking slightly which would make all the voltages read low.
If the meter is not sticking slightly, then there will be a wire wound resistor inside the meter housing which could be made smaller by paralleling it with another resistor.


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 Post subject: Re: TRIPLETT 630-NA Type 3
PostPosted: Apr Wed 08, 2020 2:29 pm 
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Joined: Mar Sat 03, 2007 12:53 am
Posts: 797
Some time ago I restored a triplett 630-NA. These are all the things that I can remember about this restoration. First I cleaned all the corrosion around the battery holders and wires that was caused by the ohmmeter battery. Then I replaced two series ohmmeter resistors on the 1x and the 100x ranges that were burnt out and verified that all the resistors were ok. Then using a calibrator, the DC full scale voltages were low. Then I applied a voltage that made the meter go from 0 to 80% full scale, removed the voltage and applied a voltage that makes the meter go from 0 to 100% full scale and then applied the first voltage which should made the meter go from 100% full scale to 80% full scale. However, it did not go all way back because there less inertia because of the smaller arc to be traversed. Then I applied a square wave (probably about 3 hz) through a current limiting resistance that made the meter repeatedly sweep from 0 to full scale for a long time (an hour or so). Afterward the previous test the meter would go all the way back to 80% and continues to do so to this day. If this did not work, I would have removed the meter face plate and loosened the pivot screw an extremely small amount and performed the test. Interestingly enough, everything worked correctly except for the measurements on highest ohmmeter ranges. I cleaned the contacts of the rotary switch and the problem persisted. I noticed that lead from one of the factory installed resistors was not straight and over time it caused the alignment of the rotary switch contact to be slightly off. I bent it so that the alignment of the rotary switch contact was correct and everything worked.

There are a number of things that could cause the problem of the DC voltages reading low which is why a step by step investigation is required. I have had meters with week springs, weak magnets, slightly high resistance in meter inside wiring, etc.


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 Post subject: Re: TRIPLETT 630-NA Type 3
PostPosted: Apr Thu 09, 2020 12:57 am 
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I had one that read low on DC and I ended up padding a resistor to bring it down to the rated value, versus trying to locate a 1% resistor replacement on the open market. I think it was R18? A 55k resistor that was reading a bit high and in it's position it would have affected all DC ranges. I don't think the meter is "perfect" now, but it is closer and presumably within tolerance. But I like a meter that can be calibrated. I think I needed a 2 or 2.2 meg resistor across it. And I don't have a huge selection of small resistors in the 1+ to 10 meg range on hand. I wonder about other issues in those meters like does the magnet get weak over time etc. besides some of the old resistors drifting more than modern film types.

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 Post subject: Re: TRIPLETT 630-NA Type 3
PostPosted: Apr Thu 09, 2020 2:44 am 
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Joined: Mar Sat 03, 2007 12:53 am
Posts: 797
Except for the ohm-meter pot limiting resistor, the resistors in the triplett 630-NA are precision wire wound resistors most with .5 % tolerance, a couple with .25% tolerance and a couple with 1% tolerance. Unless the input to the meter is overloaded, these resistors should not drift significantly over time usually less than film types. R18 is used in the V/A over 2 circuity and should only affect 1/2 of the measurements.


Last edited by Alan S on Apr Thu 09, 2020 2:57 am, edited 1 time in total.

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 Post subject: Re: TRIPLETT 630-NA Type 3
PostPosted: Apr Thu 09, 2020 2:49 am 
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Mine is the old all bakelite case style. Without the separate clear meter bezel. The resistors are all some kind of shiny black things. I know they used stuff like Dale metal film in later Simpsons and those are pretty very long term stable. Unless fried.

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 Post subject: Re: TRIPLETT 630-NA Type 3
PostPosted: Apr Fri 10, 2020 5:34 am 
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Edited to correct the info. See note below. I originally reported measurements of my 630-NS which at 100K ohms per volt has ten times the sensitivity of the 630-NA which has 10K ohms per volt sensitivity (and is switch selectable to 20K ohms per volt.

For the 630-NA:
Set your Fluke on resistance. Connect to the 630NA on DC and check the readings. Should be 10K ohms for each volt. Should read 6K on the 0.6 scale, 30K on the 3 volt scale, etc.

This trick works with every VOM including 1K ohm per volt and 20K ohm per volt and lets you know the accuracy of its resistors.

A Triplett 630-NS (at 100K ohms per volt) and the Fluke 87 are my daily drivers.

-- Rich


Last edited by tubeR on Apr Sat 11, 2020 5:04 am, edited 1 time in total.

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 Post subject: Re: TRIPLETT 630-NA Type 3
PostPosted: Apr Fri 10, 2020 6:33 pm 
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Joined: Mar Thu 29, 2018 3:41 am
Posts: 265
Location: Portland Oregon
Hi Rich,

THis is a great idea. I have a fluke 189 that has the ability to read much higher resistances than your 87. I just acquired about 10 VOM's, a number of Triplet 630-NA, a couple of Simpsons 270's, etc.

I measured the following on one of my 630 - NA's:

Fluke (Ohms)/630-NA range

6.024KOhm/0.6VDC
30.52KOhm/3.0VDC
121.55KOhm/12.0VDC
.6094MOhm/60.VDC
3.135MOhm/300VDC
12.46MOhm/600VDC
49.1 MOhm/1200VDC

I believe that the resistance is 10,000X the voltage range, not 100,000X for 0.6VDC to 300VDC and 20000X for the 600VDC. Is that correct? The 1200VDC is a weird number - like 40000X. I'll have to look at the schematic much closer.

BTW, in the schematic, what is CRA1? None of the values are listed in there so it is really hard to trace this out.

Dave


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 Post subject: Re: TRIPLETT 630-NA Type 3
PostPosted: Apr Sat 11, 2020 3:31 am 
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Joined: May Wed 06, 2009 7:01 pm
Posts: 865
Hi Dave,

You are absolutely right and your readings are correct. My error. My Triplett daily driver is a 630-NS which indeed has a spec of 100K ohms per volt and 200K ohms in the range doubler position. The 630-NA has a lesser sensitivity at 10K ohms per volt, with 20K ohms per volt in range doubler.

I have several Triplett 630 series, my favorite VOMs. Can't pass up one with a good meter but rotted battery terminals and broken glass for a dollar (hamfest purchase last year). It's easy enough to replace the battery holder with two or three AA cells in parallel inside a plastic pill bottle with wires sticking out to wire nuts. Fits in place of the battery. Three series-wired 9 volt batteries are easy enough to locate inside to replace a thirty volt special cell. A piece of acrylic cut from a CD case replaced the glass. A buck well spent for another spare meter.

Just checked its 1200 volt DC resistance (20K ohm per volt) with the Fluke. Its 23.80 megohms, about 0.8% low, thus might read a tiny bit high on that scale, but close enough to the spec. And what do you want for a buck.

Stay safe,
-- Rich


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 Post subject: Re: TRIPLETT 630-NA Type 3
PostPosted: Apr Sat 11, 2020 3:41 pm 
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Joined: May Wed 15, 2019 10:50 am
Posts: 149
Location: Charlotte, NC 28205
tubeR wrote:
Edited to correct the info. See note below. I originally reported measurements of my 630-NS which at 100K ohms per volt has ten times the sensitivity of the 630-NA which has 10K ohms per volt sensitivity (and is switch selectable to 20K ohms per volt.

For the 630-NA:
Set your Fluke on resistance. Connect to the 630NA on DC and check the readings. Should be 10K ohms for each volt. Should read 6K on the 0.6 scale, 30K on the 3 volt scale, etc.

This trick works with every VOM including 1K ohm per volt and 20K ohm per volt and lets you know the accuracy of its resistors.

A Triplett 630-NS (at 100K ohms per volt) and the Fluke 87 are my daily drivers.

-- Rich

RIich,

Thank you for this post.

Here are the DC ranges resistance readings of my 630-NA using a fluke 289:

VDC range / Fluke ohms [to 3 significant figures]
_________ ___________

00.60 VCD / 6.14K
03.00 VDC / 30.2K
012.0 VDC / 120.K
060.0 VDC / 601.K
0300. VDC / 2.99M
1200. VDC / 11.9M

Do these results show that I have one [series] resistor that's high or more ?

Thanks,

Jack Cureton


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 Post subject: Re: TRIPLETT 630-NA Type 3
PostPosted: Apr Sat 11, 2020 8:29 pm 
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Jack Cureton wrote:
Do these results show that I have one [series] resistor that's high or more?

No, not in the voltage dividers. You say you have a 5% low error on all voltage ranges, and those resistances are not 5% high.

Telling us whether the current ranges are also 5% low would help us diagnose the problem.

Also, is the error the same on the voltage and current ranges when the range doubler is activated?

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