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Hi all,
My trusty HP 400E voltmeter has developed a sticky needle. It occasionally sticks at around 2/3 deflection and needs a tap or a large voltage change to dislodge it. The needle is not contacting the front of the meter or the legend. I've done the old "washing up liquid wipedown" to remove static but that didn't work. I checked the DC output on the back of the meter to see if it was electrical rather than mechanical but that's fine.
Does anyone have any idea how to safely approach this problem without damaging the movement?
Best regards,
Chris
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Bonjour the paint and legend ink on D'Arsonval meter movements from 1970..1990 epoch can craze and a tiny flak enters the meter movement.
the close spacing between the magnet poles and armature traps a flake.
protect bench with a towel, Turn meter on its face, Tapp rear of movement lightly to dislodge the flake
if you are lucky, the errant flake will fall on the meter plastic face.
if still sticks, just Keep trying, also run the meter up and down scale
This technique has worked for me meant times
Bon courage
Jon
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Thanks for the info. I will try that later if I get a few minutes. The meter face on this isn't flaking unlike some HP stuff I've seen though which is unusual but hopefully it will dislodge anything in there anyway!
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Chris those are always tough and have been discussed here previously. Potentially what you are running into is a small flake of meter paint has dropped into the movement. These older meters do start to flake. Also a small bit of dirt or metal may have made its way in. It can even be a hair. Typically it requires the removal of the meter and then getting the movement out of the?case so?that all sides of the?meter can be looked at.? Then in a very clean area not the typical work bench see whats?up. Things like small bits of paper to work the grunge?out work. Nothing metal. If something actually has happened to the?jewel thats?a big problem. Do not mess with those?small screws as tempting as that is. Good luck Paul WB8TSL
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Thanks for the further tips. I've got an extremely clean workspace and used to work in a semi lab clean room so will take all reasonable precautions (have face shield, gloves, lint free cleaning stuff, decent plastic surface to work on available)
Will knock up a test rig with my AWG so I can slowly exercise the movement outside of the meter chassis first...
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Ok further discovery. It is peeling and that was getting in the way of the needle. Just couldn’t see it. I’ve tried the preemptive fix of applying a bit of pritt stick melted in boiling water to the edge. Used this before on gelatin legends. This sticks the flakes down with minimal risk. Fingers crossed.?
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Well the Pritt stick melted in hot water did a really good job of the peeling. Looks excellent! However it's still sticking. I will disassemble it again tomorrow and investigate further. 
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You will probably find some of the flakes stuck in the meter movement. Worst case, you will find some steel filings stuck in the meter movement.
Cheers ????
Bruce
Quoting bd139 <me@...>:
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Well the Pritt stick melted in hot water did a really good job of the peeling. Looks excellent! However it's still sticking. I will disassemble it again tomorrow and investigate further.
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I would think that other glues might be more easily used.
For instance, a famous very old glue is milk. A drop of
milk will hold very well, but is also water soluble.
Milk is the original ingredient in white glues such as
Elmer's... which is why the bottle has a cow on it.
Back when I was brewing beer, I used milk to glue the labels
onto the bottles. I just put some in a saucer, and dipped
the label in, and onto the bottle.
I have a current meter that has the dial card flaking problem,
I think I will try a little milk on a soft brush..
-Chuck Harris
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On Sat, 17 Sep 2022 15:09:51 -0700 "bd139" <me@...> wrote: Well the Pritt stick melted in hot water did a really good job of the
peeling. Looks excellent! However it's still sticking. I will
disassemble it again tomorrow and investigate further.
Attachments:
IMG_2548.JPG:
/g/HP-Agilent-Keysight-equipment/attachment/129583/
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Ok victory announced. The display remains stuck down after 24 hours which is good. The sticky was sorted by very carefully blowing the movement out with an air duster and then working around the armature and 0 and full deflection with an anti static brush. Works fine now. Thanks for the suggestions everyone :) 
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?I saved this one from the scrap heap. The face plate was pretty bad, I came out better than I thought it would. I just flaked off the parts that I new I couldn't save. One it cracked it started to curl so I just broke off what was loose, if it was going towards a number or line I used my exacto knife to cut it so as to not lose anything important. Then I just put clear Krylon over it to hopefully hold everything in place. Some of the face plate curled up so high the needle could not move past it. 
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I have a dozen of these meters (mostly power meters) rescued from scrap, about half of them have the faceplate going in flakes, one or two badly.
I've heard about a mysterious "Krylon" (that I don't have), about Milk (that I have), and about a method with the Pritt stick (that I have, too).
What else?
How exactly did you do it with the Pritt-Stick method?
What is Krylon? Is there something similar I can find in EU / Germany?
I'm tempted to try the milk thing... what is the best way to proceed - spraying it on the faceplate and let it sit in?
I've repaired such a faceplate once many years ago and do not remember anymore how. I must have scanned it, and printed it somehow. I sold it, so I cannot check.
cheers
Martin
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toggle quoted message
Show quoted text
I have a dozen of these meters (mostly power meters) rescued from scrap, about half of them have the faceplate going in flakes, one or two badly.
I've heard about a mysterious "Krylon" (that I don't have), about Milk (that I have), and about a method with the Pritt stick (that I have, too).
What else?
How exactly did you do it with the Pritt-Stick method?
What is Krylon? Is there something similar I can find in EU / Germany?
I'm tempted to try the milk thing... what is the best way to proceed - spraying it on the faceplate and let it sit in?
I've repaired such a faceplate once many years ago and do not remember anymore how. I must have scanned it, and printed it somehow. I sold it, so I cannot check.
cheers
Martin
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Krylon is a clear spray paint (pressurized can). It is a product name, perhaps a different name in Germany.
Cheers!
Bruce
Quoting David Holland <david.w.holland@...>:
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Clear acrylic spray....
On Mon, Sep 19, 2022 at 10:49 AM Martin via groups.io <musaeum=
[email protected]> wrote:
I have a dozen of these meters (mostly power meters) rescued from scrap,
about half of them have the faceplate going in flakes, one or two badly.
I've heard about a mysterious "Krylon" (that I don't have), about Milk
(that I have), and about a method with the Pritt stick (that I have, too).
What else?
How exactly did you do it with the Pritt-Stick method?
What is Krylon? Is there something similar I can find in EU / Germany?
I'm tempted to try the milk thing... what is the best way to proceed -
spraying it on the faceplate and let it sit in?
I've repaired such a faceplate once many years ago and do not remember
anymore how. I must have scanned it, and printed it somehow. I sold it, so
I cannot check.
cheers
Martin
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When I was bringing a Tektronix 130 LC meter back to life, I took a precaution which enables me to fix this problem a different way. Since I have excellent macrophotography capabilities, I was able to remove the scale and make an undistorted photograph of it. When the original scale finally bites the dust, I will be able to edit out the any developing flakes and other defects in the photo and print it (1:1) on high quality paper, which will, then, be glued to a thin hard aluminum sheet, drilled and cut to fit the meter exactly. I'll probably use 3M Super 77 adhesive.
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be careful of the
out-gassing from the adhesive- 77 has plenty of out-gassing.
搁别苍é别
On 9/19/22 10:45 AM, SCMenasian wrote:
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When I was bringing a Tektronix 130 LC meter back to life, I took
a precaution which enables me to fix this problem a different way.
Since I have excellent macrophotography capabilities, I was able
to remove the scale and make an undistorted photograph of it. When
the original scale finally bites the dust, I will be able to edit
out the any developing flakes and other defects in the photo and
print it (1:1) on high quality paper, which will, then, be glued
to a thin hard aluminum sheet, drilled and cut to fit the meter
exactly. I'll probably use 3M Super 77 adhesive.
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Krylon? is a.brand name for spray paint.? ?It comes in many colors.? ?A web search should find it.
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-------- Original message -------- From: Bruce <bruce@...> Date: 9/19/22 10:32 AM (GMT-08:00) Subject: Re: [HP-Agilent-Keysight-equipment] HP 400E sticky needle
Krylon is a clear spray paint (pressurized can).? It is a product? name, perhaps a different name in Germany. Cheers! Bruce Quoting David Holland <david.w.holland@...>: > Clear acrylic spray.... > > https://www.amazon.com/Krylon-K01303A07-Crystal-Acrylic-Coating/dp/B001K65K26 > > On Mon, Sep 19, 2022 at 10:49 AM Martin via groups.io <musaeum= > [email protected]> wrote: > >> I have a dozen of these meters (mostly power meters) rescued from scrap, >> about half of them have the faceplate going in flakes, one or two badly. >> >> I've heard about a mysterious "Krylon" (that I don't have), about Milk >> (that I have), and about a method with the Pritt stick (that I have, too). >> What else? >> >> How exactly did you do it with the Pritt-Stick method? >> What is Krylon? Is there something similar I can find in EU / Germany? >> >> I'm tempted to try the milk thing... what is the best way to proceed - >> spraying it on the faceplate and let it sit in? >> >> I've repaired such a faceplate once many years ago and do not remember >> anymore how. I must have scanned it, and printed it somehow. I sold it, so >> I cannot check. >> >> cheers >> Martin >> >> >> >> >> >> >> > > >
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On Mon, Sep 19, 2022 at 03:49 PM, Martin wrote:
How exactly did you do it with the Pritt-Stick method?
Fairly simple. I cut a chunk off a pritt stick and popped it into the bottom of a small plastic food container. Poured enough hot water on the top of it to dissolve it and turn it into a very watery paste. This was then applied to the peeling edges with a whittled down chopstick with a slit cut into the end. The capillary action sucked the diluted adhesive down onto the meter face and the lifted paint instantly rolled back down onto the surface. It was left to dry in the sun inside a plastic zip lock bag with a couple of silica gel packs in it and some cardboard to support the side of the bags so that it didn't touch the meter face. ? Worked better than I expected it to!
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I haven't tried fixing a meter with milk yet. But I would do something very much like what BD139 said. I think the idea is to put a small drop for each flake, and encourage the flake to stick to the drop by surface tension. Use a tooth pick to encourage the flakes into the proper alignment. I don't think they will need much encouragement. I think with either of these methods, less is more. Don't spray, don't flood, just a tiny drop. You want the drop to disappear when the flake is pulled down by the surface tension. Be sure you have enough light and magnification so that you can easily see what you are doing! -Chuck Harris On Mon, 19 Sep 2022 11:06:53 -0400 "David Holland" <david.w.holland@...> wrote: Clear acrylic spray....
On Mon, Sep 19, 2022 at 10:49 AM Martin via groups.io <musaeum=
[email protected]> wrote:
I have a dozen of these meters (mostly power meters) rescued from
scrap, about half of them have the faceplate going in flakes, one
or two badly.
I've heard about a mysterious "Krylon" (that I don't have), about
Milk (that I have), and about a method with the Pritt stick (that I
have, too). What else?
How exactly did you do it with the Pritt-Stick method?
What is Krylon? Is there something similar I can find in EU /
Germany?
I'm tempted to try the milk thing... what is the best way to
proceed - spraying it on the faceplate and let it sit in?
I've repaired such a faceplate once many years ago and do not
remember anymore how. I must have scanned it, and printed it
somehow. I sold it, so I cannot check.
cheers
Martin
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Thanks a lot for the details!
So the dilution seems to be something like 1:20 in volume...
Did you use tap water, or distilled water?
Sorry to be picky, its just that I fear of making it worse if the conditions are not right.
I had poor grades in chemistry... ;-)
cheers
Martin
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Froggie the Gremlin
Martin