Maker Pro
Maker Pro

Triplet 630APL meter movement adjustment

I just picked up this meter today at a flea market. At the time of
purchase I noted that the two tiny screws that held the dial plate to
the movement had come loose and were floating around the meter dial.
The dial plate however was secure. I also noted that mechanical zero
was the same whether the meter was standind up or laying down. So I
took a chance on it and it turns out except for a bit of old battery
corrosion, it seemed to work great. When I got it home I removed the
clear plastic cover and then the dial to make sure I retrieved the
tiny screws and any washers that may have come off as well. While
securing the dial back to the meter my small screwdriver slipped at
about the 2 oclock position and.went in and hit the magnet. It didn't
seem to damage anything. After everything was re assembled I tweaked
mechanical zero with the unit in the vertical position and took a
known voltage reading with it. The reading after the accident read the
same as before. It was then that I laid the meter on its back and
noticed that now mechanical zero drifts abot.250 inch downward.
Raising it back up to vertical put the needle back to zero. I know
that I must have done this because it was fine before I slipped. I
know that the tiny counter weight springs which are located at 9, 3,
and 6 oclock have something to do with this delicate balance and I
would like to try to adjust them but I don't know what the procedure
is for making this adjustment so I don't want to make things worse or
destroy the movement completely. Can anyone familiar with adjusting
these movements please advise me on this? Thanks, Lenny
 
S

Samuel M. Goldwasser

Jan 1, 1970
0
I just picked up this meter today at a flea market. At the time of
purchase I noted that the two tiny screws that held the dial plate to
the movement had come loose and were floating around the meter dial.
The dial plate however was secure. I also noted that mechanical zero
was the same whether the meter was standind up or laying down. So I
took a chance on it and it turns out except for a bit of old battery
corrosion, it seemed to work great. When I got it home I removed the
clear plastic cover and then the dial to make sure I retrieved the
tiny screws and any washers that may have come off as well. While
securing the dial back to the meter my small screwdriver slipped at
about the 2 oclock position and.went in and hit the magnet. It didn't
seem to damage anything. After everything was re assembled I tweaked
mechanical zero with the unit in the vertical position and took a
known voltage reading with it. The reading after the accident read the
same as before. It was then that I laid the meter on its back and
noticed that now mechanical zero drifts abot.250 inch downward.
Raising it back up to vertical put the needle back to zero. I know
that I must have done this because it was fine before I slipped. I
know that the tiny counter weight springs which are located at 9, 3,
and 6 oclock have something to do with this delicate balance and I
would like to try to adjust them but I don't know what the procedure
is for making this adjustment so I don't want to make things worse or
destroy the movement completely. Can anyone familiar with adjusting
these movements please advise me on this? Thanks, Lenny

If it's horizontal, those weights have no effect.

If it's vertical, the bottom needs to balance the moment arm of the
needle.

With the needle moving downward (to the left), it means the needle is
heavy relative to the counterbalance.

But I doubt the screwdriver incident did this unless it knocked one
of the weights and bent the pin it was on.

--
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S

Samuel M. Goldwasser

Jan 1, 1970
0
Dave M said:
You are correct in saying that the balance of the movement is delicate. The
tail weights are critical to the accuracy of your meter.
There are three weights on the bottom (tail) of the meter pointer; the tail
weight (on the bottom of the shaft of the pointer) and two side weights (on
the cross-bar). I used to service these meters while working at a
commercial cal lab in the late 60s.
The procedure for balancing a movement is thus:
(1) Center the mechanical zero tang so that it is in the middle of its
range.
(2) Position the meter so that the pointer is level horizontally. Adjust
the tail weight so that the pointer rests on the zero mark on the scale

This is a bit confusing. Do you mean that the pivot is also horizontal,
or that the entire meter is on its back? If the meter is on its back,
then the zero position is determined entirely by the mechanical zero
adjusting the hair spring. The weights should have no effect.

If you mean pivot is horizontal with the needle also horizontal, tt seems
like there is a step missing:

(1a) With the meter on its back, adjust the rear mechanical zero so that the
needle rests on the zero mark.
(3) Position the meter so that the pointer is vertical. Adjust the side
weights so that the pointer rests on the zero mark on the scale.
(4) Position the meter so that it sits upright on the bench (pointer is at
45 deg). If the pointer doesn't come to exactly zero scale, more adjustment
is needed.
(5) Repeat steps 3 & 4 until the pointer is at zero in all positions.

You'll find that balance will be easier if you leave the tail weight alone
after the initial balance (Step 1) and use the side weights to do the final
trimming adjustments. You'll have to move the side weights inward or
outward in unison to maintain the vertical balance. Make the adjustments in
very small increments.

Keep in mind the principles of balancing a lever on a fulcrum; the heavier
end will move down. The pointer's pivot is the fulcrum. The most difficult
part of the procedure is to make the pointer balance when the instrument is
upright on the bench. If the pointer is below the scale zero, then the side
weights need to be moved out.

This is exactly what's being done, thus the confusion. :)

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You are correct in saying that the balance of the movement is delicate.  The
tail weights are critical to the accuracy of your meter.
There are three weights on the bottom (tail) of the meter pointer; the tail
weight (on the bottom of the shaft of the pointer) and two side weights (on
the cross-bar).  I used to service these meters while working at a
commercial cal lab in the late 60s.
The procedure for balancing a movement is thus:
(1) Center the mechanical zero tang so that it is in the middle of its
range.
(2) Position the meter so that the pointer is level horizontally.  Adjust
the tail weight so that the pointer rests on the zero mark on the scale
(3) Position the meter so that the pointer is vertical.  Adjust the side
weights so that the pointer rests on the zero mark on the scale.
(4) Position the meter so that it sits upright on the bench (pointer is at
45 deg).  If the pointer doesn't come to exactly zero scale, more adjustment
is needed.
(5) Repeat steps 3 & 4 until the pointer is at zero in all positions.

You'll find that balance will be easier if you leave the tail weight alone
after the initial balance (Step 1) and use the side weights to do the final
trimming adjustments.  You'll have to move the side weights inward or
outward in unison to maintain the vertical balance.  Make the adjustments in
very small increments.

Keep in mind the principles of balancing a lever on a fulcrum; the heavier
end will move down. The pointer's pivot is the fulcrum.  The most difficult
part of the procedure is to make the pointer balance when the instrument is
upright on the bench.  If the pointer is below the scale zero, then theside
weights need to be moved out.

Hth,

--
"In theory, there isn't any difference between theory and practice.  In
practice, there is."  - Yogi Berra

Dave M
masondg44 at comcast dot net- Hide quoted text -

- Show quoted text -

I wanted to update this message and also perhaps clarify a few things.
It now seems that mechanical zero on the left side is pretty close to
being the same both in vertical and horizontal position. I don't know
what caused this to change but it apparently did. However now when
zeroing the pointer on ohms to the right, in vertical position, as you
normally would, I set the pot to deflect the pointer to right zero.
Leaving the input shorted, I then turned the meter horizontal and
noted that the needle moved about .250 inch to the right. It would
appear that this is a more serious problem now . In the former
scenario in my first post, though a pain in the ass, mechanical zero
could be tweaked each time, depending upon the operating position of
the instrument. However in this case, accuracy is definitly seems like
it would be affected. I never considered the possibility of a "right
side" problem. In addition, these spring weights are very tight and
almost impossible to move. Perhaps my slip up didn't cause this
deflection problem in the first place. I never looked at this aspect
of operation. In any case though I don't know what to do about this.
I also have a question:
In step two, with the meter horizontal you said to adjust the tail
weight so that indication is zero. As Sam has previously mentioned, in
horizontal position, why would any weights affect the pointer's
position? Lenny.
 
I wanted to update this message and also perhaps clarify a few things.
It now seems that mechanical zero on the left side is pretty close to
being the same both in vertical and horizontal position. I don't know
what caused this to change but it apparently did. However now when
zeroing the pointer on ohms to the right, in vertical position, as you
normally would, I set the pot to deflect the pointer to right zero.
Leaving the input shorted, I then turned the meter horizontal and
noted that the needle moved about .250 inch to the right. It would
appear that this is a more serious problem now . In the former
scenario in my first post, though a pain in the ass, mechanical zero
could be tweaked each time, depending upon the operating position of
the instrument. However in this case, accuracy is definitly seems like
it would be affected. I never considered the possibility of a "right
side" problem. In addition, these spring weights are very tight and
almost impossible to move. Perhaps my slip up didn't cause this
deflection problem in the first place. I never looked at this aspect
of operation.  In any case though I don't know what to do about this.
I also have a question:
In step two, with the meter horizontal you said to adjust the tail
weight so that indication is zero. As Sam has previously mentioned, in
horizontal position, why would any weights affect the pointer's
position? Lenny.- Hide quoted text -

- Show quoted text -

Just another note here. When I say "vertical position" I mean the
instrument is standing up on the bench. In "horizontal position" the
meter is on its back. Sorry for the confusion. Lenny
 
No..  the meter is not on its back; rather, stand it on the bottom left
corner.  The instrument should be held in front of you so that you are
looking squarely at it.  The meter should be positioned so that the pointer
is level horizontally, and pointing to your left.

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Sorry for the drawing... it's the best I can do without a ruler & compass..
<g>







Sorry for the confusion.  Hope this helped to clear it up.

--
"In theory, there isn't any difference between theory and practice.  In
practice, there is."  - Yogi Berra

Dave M
masondg44 at comcast dot net- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

Dave
I don't mean to be a pain but I'm trying to understand your last post.
I think I understand what you've written but I'm not so sure about the
drawing though. From what you said, I position the meter standing up
in front of me. I then rotate the entire instrument 45 degrees to the
left. The needle is now horizontal. At this point I adjust mechanical
zero. Then I stand the meter back up (rotate instrument 45 degrees to
the right) to see if zero is still the same?
Well I did that and mechanical zero moves downscale,(left) when the
meter is stood back up. Now to fix this am I correct to assume that
the right side weight would have to be moved out slightly? And if I
were to do this could it affect anything else? Or am I misconstuing
the theory of the procedure? Lenny.
 
S

Samuel M. Goldwasser

Jan 1, 1970
0
Dave
I don't mean to be a pain but I'm trying to understand your last post.
I think I understand what you've written but I'm not so sure about the
drawing though. From what you said, I position the meter standing up
in front of me. I then rotate the entire instrument 45 degrees to the
left. The needle is now horizontal. At this point I adjust mechanical
zero. Then I stand the meter back up (rotate instrument 45 degrees to
the right) to see if zero is still the same?
Well I did that and mechanical zero moves downscale,(left) when the
meter is stood back up. Now to fix this am I correct to assume that
the right side weight would have to be moved out slightly? And if I
were to do this could it affect anything else? Or am I misconstuing
the theory of the procedure? Lenny.

Here is how I've interpreted and edited what has been written:

1. Center the front mechanical zero tang so that it is in the middle of its
range.

2. With the meter flat on its back (pivot axis vertical), adjust the rear
mechanical zero tang so that the needle rests on the zero mark.

If easy access to the rear adjustment is not possible, simply adjust the
front mechanical zero tang so the needle rests on the zero mark.

Since the pivot axis is vertical, only the mechanical (hair spring)
adjustments matter.

3. Position the meter so that the pointer is level horizontally. To clarify,
this means the pivot axis is horizontal and the entire meter is oriented at
about 45 degrees (on most meters) with the needle pointing to the left
horizontally. Adjust the tail weight so that the pointer rests on the
zero mark on the scale.

Only the mechanical zero (performed in steps 1 and 2) and balance between
the needle and tail weight matter.

4. Position the meter so that the pointer is vertical. Adjust the side
weights so that the pointer rests on the zero mark on the scale.

(Only the mechanical zero (performed in steps 1 and 2) and balance between
the two side weights matter.)

5. Position the meter so that it sits upright on the bench (pivot axis is
horizontal, pointer is at 45 degrees). If the pointer doesn't come to
exactly zero scale, more adjustment is needed.

6. Repeat steps (4) and (5) until the pointer is at zero in all positions.

As has been said, think about what you're trying to do - balance a
rotating mass.

Suggestions/improvement welcome.

--
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Here is how I've interpreted and edited what has been written:

1. Center the front mechanical zero tang so that it is in the middle of its
   range.

2. With the meter flat on its back (pivot axis vertical), adjust the rear
   mechanical zero tang so that the needle rests on the zero mark.

   If easy access to the rear adjustment is not possible, simply adjust the
   front mechanical zero tang so the needle rests on the zero mark.

   Since the pivot axis is vertical, only the mechanical (hair spring)
   adjustments matter.

3. Position the meter so that the pointer is level horizontally.  To clarify,
   this means the pivot axis is horizontal and the entire meter is oriented at
   about 45 degrees (on most meters) with the needle pointing to the left
   horizontally.  Adjust the tail weight so that the pointer rests on the
   zero mark on the scale.

   Only the mechanical zero (performed in steps 1 and 2) and balance between
   the needle and tail weight matter.

4. Position the meter so that the pointer is vertical.  Adjust the side
   weights so that the pointer rests on the zero mark on the scale.

   (Only the mechanical zero (performed in steps 1 and 2) and balancebetween
   the two side weights matter.)

5. Position the meter so that it sits upright on the bench (pivot axis is
   horizontal, pointer is at 45 degrees).  If the pointer doesn't come to
   exactly zero scale, more adjustment is needed.

6. Repeat steps (4) and (5) until the pointer is at zero in all positions..

As has been said, think about what you're trying to do - balance a
rotating mass.

Suggestions/improvement welcome.

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I think that I understand the mechanics of this now. I'll give it a
try. The springs are really tight We''ll see. Thanks, Lenny
 
B

Bob Larter

Jan 1, 1970
0
Samuel said:
If it's horizontal, those weights have no effect.

If it's vertical, the bottom needs to balance the moment arm of the
needle.

With the needle moving downward (to the left), it means the needle is
heavy relative to the counterbalance.

But I doubt the screwdriver incident did this unless it knocked one
of the weights and bent the pin it was on.

It's pretty normal for a meter to read a little differently between
horizontal & vertical. Touching the magnet shouldn't cause any problems.
 
I think that I understand the mechanics of this now. I'll give it a
try. The springs are really tight We''ll see. Thanks, Lenny

Thanks for helping with the explanation, Sam.  I had in my mind what I
wanted to say; guess it came out a little confused.  Comes with age..

Cheers!!

--
"In theory, there isn't any difference between theory and practice.  In
practice, there is."  - Yogi Berra

Dave M
masondg44 at comcast dot net- Hide quoted text -

- Show quoted text -

Well I made the adjustments as both Sam and Dave suggested. I want to
thank both of you guys for all the advice. I could never have done
this without your help. It was very difficult, but now balance in all
planes is very close. In fact its as close if not better than my bench
VOM. During the course of the procedure one side spring became so
distorted that it was useless, and the other simply launched itself
while I was holding it with the hemostat. Luckily I have a box of junk
260's and was able to scrounge two springs from an old movement. I'm
glad that I learned how to do this but I don't want to have to do it
again. You can easily destroy a movement with one careless.slip. Now
that the mechanical is resolved I have to deal with an electrical
problem. All AC ranges are inoperative. I found one resistor which was
burned beyond recognition and was open but I have no schematic so I
cannot troubleshoot this instrument. I also found out that Triplett
was sold two years ago ironically to Jewell Instruments, a company
here in New Hampshire. I called them today but they have little if
nothing to do with older equipment. No schematics either. Does anyone
know where I might be able to find a manual for a model
630APL? . .Thanks, Lenny
 
S

Samuel M. Goldwasser

Jan 1, 1970
0
Well I made the adjustments as both Sam and Dave suggested. I want to
thank both of you guys for all the advice. I could never have done
this without your help. It was very difficult, but now balance in all
planes is very close. In fact its as close if not better than my bench
VOM. During the course of the procedure one side spring became so
distorted that it was useless, and the other simply launched itself
while I was holding it with the hemostat. Luckily I have a box of junk
260's and was able to scrounge two springs from an old movement. I'm
glad that I learned how to do this but I don't want to have to do it
again. You can easily destroy a movement with one careless.slip. Now
that the mechanical is resolved I have to deal with an electrical
problem. All AC ranges are inoperative. I found one resistor which was
burned beyond recognition and was open but I have no schematic so I
cannot troubleshoot this instrument. I also found out that Triplett
was sold two years ago ironically to Jewell Instruments, a company
here in New Hampshire. I called them today but they have little if
nothing to do with older equipment. No schematics either. Does anyone
know where I might be able to find a manual for a model
630APL? . .Thanks, Lenny

Assuming that only the one resistor is bad, estimate a replacement
based on the ohms/V rating of the meter. Start high and work down
if there is any response. If nothing else is smoked, you should be
able to figure it out. Real engineers don't need !@$# schematics! :)

--
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Assuming that only the one resistor is bad, estimate a replacement
based on the ohms/V rating of the meter.  Start high and work down
if there is any response.  If nothing else is smoked, you should be
able to figure it out.  Real engineers don't need !@$# schematics! :)

--
    sam | Sci.Electronics.Repair FAQ:http://www.repairfaq.org/
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- Show quoted text -

Yeah I tried that Sam but it appears that there is more wrong than
just that resistor. Lenny.
 
S

Samuel M. Goldwasser

Jan 1, 1970
0
Yeah I tried that Sam but it appears that there is more wrong than
just that resistor. Lenny.

Oh well, it was worth a shot....

Check the rectifier. If it got through the resistor, but DC ranges work,
that would be next in line.

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Oh well, it was worth a shot....

Check the rectifier.  If it got through the resistor, but DC ranges work,
that would be next in line.

--
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Important: Anything sent to the email address in the message header aboveis
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I checked the meter diodes and they were both shorted. They were some
obscure number that wasn't listed anywhere. So I pulled two out of an
old junk 260 that was of a similar vintage. I don't know if the
originals were silicon or germanium, if it matters but AC came right
up and the accuracy as compared to my digital was not too bad at all.
So my 1.00 flea market find needed a movement balance adjustment, it
had two burned resistors, for which I did find the values, and two
rectifiers for the AC. Someone really beat the shit out of this thing
but now that its repaired its actually pretty accurate. For the 30V
battery, I used four 6.50 V small lithium military surplus batteries.
Each battery is half the size of an aa battery. I soldered them
together and fit them inside the case. This was a nice little project.
Thanks again everyone. Lenny.
 
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