amprobe repair

[Littleberry]

The needle on my vintage
amprobe will not move
(I suspect it is stuck).

Of course, I use a line splitter
(as always) against a hefty
current (space heater) to make
sure, but, the needle just
won't move (using the adjustment
confirms a probable stuck needle).

I don't see anyway to open the
amprobe up. There are two tiny
plastic-looking hex-type nuts
on the back, but they are surrounded
by short plastic tubes that are too
close for any socket to get into.
It looks like you need a special
tool to open it up - does anyone
know how to get into an amprobe?
Alternatively, what type of business
would likely have the expert skill
needed to make the repair?

Littleberry

 

[Asimov]

"Littleberry" bravely wrote to "All" (08 Jan 04 07:51:16)
--- on the heady topic of "amprobe repair"

I'm guessing but it seems like the magnet pole piece got jarred loose
and has ended up resting on the needle coil jamming it solid. It would
have to be examined to be certain. Basically, this is a difficult
repair for the novice. If the meter has historical/sentimental value
try an instrumentation calibration and repair place. They deal with
this stuff on a regular basis. Many such places are owner run and you
can discuss the problem directly one on one for a better opinion than
I can give you here.


Li> From: davsf@neto.com (Littleberry)

Li> The needle on my vintage
Li> amprobe will not move
Li> (I suspect it is stuck).

Li> Of course, I use a line splitter
Li> (as always) against a hefty
Li> current (space heater) to make
Li> sure, but, the needle just
Li> won't move (using the adjustment
Li> confirms a probable stuck needle).

Li> I don't see anyway to open the
Li> amprobe up. There are two tiny
Li> plastic-looking hex-type nuts
Li> on the back, but they are surrounded
Li> by short plastic tubes that are too
Li> close for any socket to get into.
Li> It looks like you need a special
Li> tool to open it up - does anyone
Li> know how to get into an amprobe?
Li> Alternatively, what type of business
Li> would likely have the expert skill
Li> needed to make the repair?

Li> Littleberry

.... Over a hundred billion electrons were used in crafting this tagline.

 

On 8 Jan 2004 07:51:16 -0800, davsf@neto.com (Littleberry) wrote:

The needle on my vintage
amprobe will not move
(I suspect it is stuck).

Of course, I use a line splitter
(as always) against a hefty
current (space heater) to make
sure, but, the needle just
won't move (using the adjustment
confirms a probable stuck needle).

I don't see anyway to open the
amprobe up. There are two tiny
plastic-looking hex-type nuts
on the back, but they are surrounded
by short plastic tubes that are too
close for any socket to get into.
It looks like you need a special
tool to open it up - does anyone
know how to get into an amprobe?
Alternatively, what type of business
would likely have the expert skill
needed to make the repair?

Littleberry

I've unscrewed those plasic hex nuts, with fine needlenose pliers.
Even using an eraser from a pencil, might work. They're metal (brass?)
threads underneath. If you get it open, I think you'll see what's
wrong. Those RS-3 (RS-1) meters are bulletproof, from my experience.
I've only found a broken wire, which required resoldering, to fix.

Remember, the two position switch on the front, is to lock the needle.
Maybe it's jammed internally.

Dwight.

 

[Littleberry]

Thanks Dwight, the fine point needlenose
and the round pencil eraser did the
trick to get those plastic hex screws out.

I couldn't tell anything right away, but,
at least now I can get it apart. I will
study it more tomorrow and see why the
needle won't move. I didn't see any
wires loose right away and the locking
switch is sort of hidden underneath -
now that I can get it open I'll go
deeper. Thanks again. A new one
only costs about $100 (this one is
at least 30 years old), but I am
hooked now on the challange.

Littleberry

 

[Dave Cole]

in article bd00fe19.0401080751.10ecbc5c@posting.google.com, Littleberry at
davsf@neto.com wrote on 1/8/04 09:51:

The needle on my vintage
amprobe will not move
(I suspect it is stuck).

LB
If I recall correctly, some of the old amprobes had a "switch" on the front
(or side?) that mechanically locked the needle. It allowed rough handling
and drops to be survived w/o suspension damage. Look carefully for one
before trying to open the case!
HTH
Dave Cole
--
When we start deceiving ourselves into thinking
not that we want something or need something,
not that it is a pragmatic necessity for us to have it,
but that it is a moral imperative that we have it,
then is when we join the fashionable madmen,
and then is when the thin whine of hysteria
is heard in the land, and then is when
we are in bad trouble.
Joan Didion