Triplett 3423 meter movement help needed
 

I've been attempting to repair the meter movement in my Triplett 3423
tube tester to correct an open circuit on the coil. The coil wasn't
fried, it just had a bad solder joint from the winding to the
"terminal" on the needle (front)side of the meter.

The meter now operates(!), although not as smoothly as it should. The
spring appears to be binding slightly due to a lack of planar
concentricity (best way I know to describe the problem), causing
sticking and poor repeatability. In other words, if you lay it on a
flat surface some sections of the spring will not lay flat, but will
stick up. I have spent a great deal of time gently poking and coercing
the spring, and while it's better than it was when I started, I just
can't seem to correct for the apparent damage I incurred when I first
ripped it apart.

So, it appears I need to replace the spring. Does anyone know of a
source for clock springs for meter movements? I don't know if there
are standard sizes, but FWIW the meter is a 4.5"x4", 100uA, 250 mV
type.

I may end up replacing the meter movement entirely, but I'd prefer to
just replace the spring as I've developed a decent skill level in
working with this stuff.

Any advice or direction as to a source for clock springs would be
greatly appreciated.

Thanks,
Sam

Been there, done that.
Are you ABSOLUTELY sure there is no foreign matter in the movement
somewhere. Frequently, some iron finings or whatever will get sucked into
the magnets. The hint is where you say: "sticking and poor repeatability".
I've seen this all too many times when sticking my nose where it doesn't
belong (I do custom meter faces). IF the spring has only planar
irregularities and the turns do not hit anything else (including adjacent
turns) I see no reason why it should "stick". Look V E R Y carefully. The
magnets are very strong and Murphy was wise.
Look where the winding bobin is when the "stick" occurs. There are a lot of
places where some foreign matter can cause this. Bobbins typically have
four sides as well as an "inside" and "outside" surface to hit slivers and
some of the clearance places are difficult to see into. Tip-toe lightly &
gud luck.
--
Steve N, K,9;d, c. i My email has no u's.


"Sam Lloyd" wrote in message
om...
I've been attempting to repair the meter movement in my Triplett 3423
tube tester to correct an open circuit on the coil. The coil wasn't
fried, it just had a bad solder joint from the winding to the
"terminal" on the needle (front)side of the meter.

The meter now operates(!), although not as smoothly as it should. The
spring appears to be binding slightly due to a lack of planar
concentricity (best way I know to describe the problem), causing
sticking and poor repeatability. In other words, if you lay it on a
flat surface some sections of the spring will not lay flat, but will
stick up. I have spent a great deal of time gently poking and coercing
the spring, and while it's better than it was when I started, I just
can't seem to correct for the apparent damage I incurred when I first
ripped it apart.

So, it appears I need to replace the spring. Does anyone know of a
source for clock springs for meter movements? I don't know if there
are standard sizes, but FWIW the meter is a 4.5"x4", 100uA, 250 mV
type.

I may end up replacing the meter movement entirely, but I'd prefer to
just replace the spring as I've developed a decent skill level in
working with this stuff.

Any advice or direction as to a source for clock springs would be
greatly appreciated.

Thanks,
Sam

Been there, done that.
Are you ABSOLUTELY sure there is no foreign matter in the movement
somewhere. Frequently, some iron finings or whatever will get sucked into
the magnets. The hint is where you say: "sticking and poor repeatability".
I've seen this all too many times when sticking my nose where it doesn't
belong (I do custom meter faces). IF the spring has only planar
irregularities and the turns do not hit anything else (including adjacent
turns) I see no reason why it should "stick". Look V E R Y carefully. The
magnets are very strong and Murphy was wise.
Look where the winding bobin is when the "stick" occurs. There are a lot of
places where some foreign matter can cause this. Bobbins typically have
four sides as well as an "inside" and "outside" surface to hit slivers and
some of the clearance places are difficult to see into. Tip-toe lightly &
gud luck.
--
Steve N, K,9;d, c. i My email has no u's.


"Sam Lloyd" wrote in message
om...
I've been attempting to repair the meter movement in my Triplett 3423
tube tester to correct an open circuit on the coil. The coil wasn't
fried, it just had a bad solder joint from the winding to the
"terminal" on the needle (front)side of the meter.

The meter now operates(!), although not as smoothly as it should. The
spring appears to be binding slightly due to a lack of planar
concentricity (best way I know to describe the problem), causing
sticking and poor repeatability. In other words, if you lay it on a
flat surface some sections of the spring will not lay flat, but will
stick up. I have spent a great deal of time gently poking and coercing
the spring, and while it's better than it was when I started, I just
can't seem to correct for the apparent damage I incurred when I first
ripped it apart.

So, it appears I need to replace the spring. Does anyone know of a
source for clock springs for meter movements? I don't know if there
are standard sizes, but FWIW the meter is a 4.5"x4", 100uA, 250 mV
type.

I may end up replacing the meter movement entirely, but I'd prefer to
just replace the spring as I've developed a decent skill level in
working with this stuff.

Any advice or direction as to a source for clock springs would be
greatly appreciated.

Thanks,
Sam

Steve,

Thanks for your comments. I suppose I haven't ruled out debris
completely, but I cleaned it pretty well with IPA when I had it apart,
then used canned air after reassembly. As you mentioned, I believe the
problem is that adjacent turns of the spring are rubbing in certain
positions, and possibly crossing, hence the "stick" problem. This is
what I was trying to say when I mentioned the planar issue originally.
It's hard to see, but it looks like there's a concentricity problem,
too- before I attach the outer end of the spring the spiral looks
fairly decent, but as soon as I move it into place and attach (solder)
the outer tip, the turns are no longer evenly radiused from the
center. Also, the travel is very smooth when the spring is removed, so
again I believe this points to the spring as the culprit.

Another thing I didn't mention before is that the meter requires
greater current to cause FSD now than it did previously. And when I
set the zero adjust it tends to under-report all readings, i.e., the
line test gives a position of around 1/4 scale rather than 1/2 scale.

Any advice?

Thanks,
Sam




"Steve Nosko" wrote in message ...
Been there, done that.
Are you ABSOLUTELY sure there is no foreign matter in the movement
somewhere. Frequently, some iron finings or whatever will get sucked into
the magnets. The hint is where you say: "sticking and poor repeatability".
I've seen this all too many times when sticking my nose where it doesn't
belong (I do custom meter faces). IF the spring has only planar
irregularities and the turns do not hit anything else (including adjacent
turns) I see no reason why it should "stick". Look V E R Y carefully. The
magnets are very strong and Murphy was wise.
Look where the winding bobin is when the "stick" occurs. There are a lot of
places where some foreign matter can cause this. Bobbins typically have
four sides as well as an "inside" and "outside" surface to hit slivers and
some of the clearance places are difficult to see into. Tip-toe lightly &
gud luck.
--
Steve N, K,9;d, c. i My email has no u's.

Steve,

Thanks for your comments. I suppose I haven't ruled out debris
completely, but I cleaned it pretty well with IPA when I had it apart,
then used canned air after reassembly. As you mentioned, I believe the
problem is that adjacent turns of the spring are rubbing in certain
positions, and possibly crossing, hence the "stick" problem. This is
what I was trying to say when I mentioned the planar issue originally.
It's hard to see, but it looks like there's a concentricity problem,
too- before I attach the outer end of the spring the spiral looks
fairly decent, but as soon as I move it into place and attach (solder)
the outer tip, the turns are no longer evenly radiused from the
center. Also, the travel is very smooth when the spring is removed, so
again I believe this points to the spring as the culprit.

Another thing I didn't mention before is that the meter requires
greater current to cause FSD now than it did previously. And when I
set the zero adjust it tends to under-report all readings, i.e., the
line test gives a position of around 1/4 scale rather than 1/2 scale.

Any advice?

Thanks,
Sam




"Steve Nosko" wrote in message ...
Been there, done that.
Are you ABSOLUTELY sure there is no foreign matter in the movement
somewhere. Frequently, some iron finings or whatever will get sucked into
the magnets. The hint is where you say: "sticking and poor repeatability".
I've seen this all too many times when sticking my nose where it doesn't
belong (I do custom meter faces). IF the spring has only planar
irregularities and the turns do not hit anything else (including adjacent
turns) I see no reason why it should "stick". Look V E R Y carefully. The
magnets are very strong and Murphy was wise.
Look where the winding bobin is when the "stick" occurs. There are a lot of
places where some foreign matter can cause this. Bobbins typically have
four sides as well as an "inside" and "outside" surface to hit slivers and
some of the clearance places are difficult to see into. Tip-toe lightly &
gud luck.
--
Steve N, K,9;d, c. i My email has no u's.