[R-390] Sticky Meter Movement

[Barry Hauser]

As Paul wrote, static is the first thing to check out.  If you move your
finger over the meter glass and the pointer "tries" to follow, then it's
static.  Gear that is shipped with plastic or bubble wrap often arrives with
a bad case of static-y meters -- or may become that way as a result of one's
initial cleanup efforts.   Put a few drops of dishwashing liquid or soap in
some water and wash down as Paul advised.  You don't have to drown the
thing.  Don't buff it dry or you'll recharge the thing.

Another possibility -- something binding against the movement -- 
particularly the spring, or applying torque to the frame when tightened into
the housing. Try loosening the housing screws a bit. See if there isn't some
binding occurring where the meter's adjustment tang links up to the screw in
the meter case, or the spring might be rubbing on the inside front surface
of the housing.  Also check that the bottom part of the pointer (below the
pivot point) isn't touching something in the housing.  If nothing is bent or
out of whack, and there is binding against the housing, then you may need to
shim it with something when reassembling, so as to back the meter movement
away from the front of the housing by a hair.

While I have a 606, I don't know offhand what the meter design is, but it's
probably one with conventional needle bearings -- possibly jeweled like
watch bearings.  When the needle tips wear or the frame expands a bit or
whatever, there could be too much play.  The meter will work freely in one
position, but bind in another.  The fix is to adjust the bearings -- and
many of the meters have adjustable bearings -- usually set with a blob of
glue or glyptol.  Avoid touching the pointer itself.  If you can tilt the
mechanism to force the jamming or sticking to occur, that's what's going on.
If this is the case, the bearing(s) need to be tightened up just a hair.
Over-do it however and you can cause damage. I've done this myself
successfully, but then it was obvious that the pointer and armature were
wobbly fore and aft -- after looking carefully at close range -- and the
movement was sticking in or out of the housing.

Also check the spring as you move the needle.  (Move the pointer by gentle
blowing on it or rotating the frame -- avoid touching it.)  Make sure the
spring is coiling and uncoiling smoothly and not twisting around or popping
in such a way that it would rub against the inside of the housing when
assembled.

Hopefully, it's just static.  If so, the meter will usually work as current
is applied, and the readings past full scale may be accurate, but it will
typically fail to zero.

Barry


----- Original Message ----- 
From: "Dulaff, Paul" <PDulaff at dpconline.com>
To: <dhallam at rapidsys.com>
Cc: "R-390 List" <r-390 at mailman.qth.net>
Sent: Monday, February 14, 2005 8:48 AM
Subject: RE: [R-390] Sticky Meter Movement


> Dave
>
> Sometimes, static electricity can build up on the front of the meter face
> and cause a meter to appear sticky. This behavior happens with plastic
meter
> enclosures. If the movement is free when the meter is out of the
enclosure,
> this may be the case. Try washing the front of the meter face with water
and
> detergent.
>
> Paul - WB2NMI
>
> -----Original Message-----
> From: r-390-bounces at mailman.qth.net
> [mailto:r-390-bounces at mailman.qth.net]On Behalf Of David C. Hallam
> Sent: Monday, February 14, 2005 8:30 AM
> To: R-390 List
> Subject: [R-390] Sticky Meter Movement
>
>
> In the past there have been threads about what to do with sticky meter
> movements.  I didn't file any of the information.
>
> Over the weekend I picked up a very nice HP 606B signal generator, but it
> has a sticky output meter.  If I take to meter off and open it up, the
> movement seems to be free and move without any problems.  When I
reassemble
> it and put it back on the panel, it is sticky.  The meter is not damaged
in
> any manner that I can see.
>
> Any suggestions about how to proceed?
>
> David C. Hallam
> KC2JD
>
>
> _____________________________________________________________
> R-390 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/r-390
> Help: http://mailman.qth.net/faq.htm
> Post: mailto:R-390 at mailman.qth.net
> Unsubscribe: http://mailman.qth.net/mailman/options/r-390
> _____________________________________________________________
> R-390 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/r-390
> Help: http://mailman.qth.net/faq.htm
> Post: mailto:R-390 at mailman.qth.net
> Unsubscribe: http://mailman.qth.net/mailman/options/r-390
>