Re: Triplet 630APL meter movement adjustment

On Apr 19, 10:30 am, captainvideo462...@xxxxxxxxx wrote:
On Apr 18, 8:48 pm, "Dave M" <masondg4...@xxxxxxxxxxx> wrote:





<captainvideo462...@xxxxxxxxx> wrote in message

news:4e227b23-e32b-4c32-b2b1-7ae294163b3e@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

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

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 the side
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.- 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
.

Relevant Pages

  • Re: Triplet 630APL meter movement adjustment
    ... was the same whether the meter was standind up or laying down. ... mechanical zero with the unit in the vertical position and took a ... There are three weights on the bottom of the meter pointer; ...
    (sci.electronics.repair)
  • Re: Triplet 630APL meter movement adjustment
    ... the movement had come loose and were floating around the meter dial. ... I also noted that mechanical zero ... There are three weights on the bottom of the meter pointer; ...
    (sci.electronics.repair)
  • Re: Triplet 630APL meter movement adjustment
    ... the movement had come loose and were floating around the meter dial. ... I also noted that mechanical zero ... There are three weights on the bottom of the meter pointer; ...
    (sci.electronics.repair)
  • Re: Triplet 630APL meter movement adjustment
    ... the movement had come loose and were floating around the meter dial. ... I also noted that mechanical zero ... There are three weights on the bottom of the meter pointer; ...
    (sci.electronics.repair)
  • Re: Triplet 630APL meter movement adjustment
    ... was the same whether the meter was standind up or laying down. ... mechanical zero with the unit in the vertical position and took a ... There are three weights on the bottom of the meter pointer; ...
    (sci.electronics.repair)