Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives :: Books
Support This Site: Contributors :: Advertise


It is currently Sep Thu 18, 2014 6:45 pm


All times are UTC [ DST ]



Post New Topic Post Reply  [ 6 posts ] 
Author Message
 Post subject: Analog meter repair
PostPosted: Mar Thu 31, 2011 4:47 am 
Member

Joined: Mar Sat 27, 2010 7:06 pm
Posts: 48
Location: Montrose, Colorado
Can anyone suggest where I might get analog meter repair work done -- specifically on a s-meter for a Hallicrafters SX-28? The meter functions electrically, but there is a problem with the movement. Hair springs look ok.


Top
 Profile  
 
 Post subject:
PostPosted: Mar Thu 31, 2011 11:05 am 
Member
User avatar

Joined: Jul Wed 22, 2009 1:46 pm
Posts: 2091
Location: Stalingrad, Connecticut
I've used Byram labs

I'm sure that others will chime in with other sources

_________________
....
.....
The Trouble with doing nothing, is that you can't tell when you're finished...


Top
 Profile  
 
 Post subject:
PostPosted: Mar Thu 31, 2011 2:30 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 6361
Location: Freeport, LI, New York 11520
Can you better elaborate on the problem?....
Here's a few ideas to entertain....

Pivot friction is probably the No.1 problem with old D'Arsonval meter movements other than broken balance springs or a burned out coil. You'll notice this problem while the meter is in operation. You can gently roll the handle end of a small screwdriver against the face of the meter and if it moves because of this, pivot friction could very well be the culprit.
Why?...
The pivot points on either side of the coil have become flattened and instead of the points sitting on their respective jewels, they are resting off-center.
The jewel cups themselves have loosened a bit. They're held in place by a nut on either side (front and back) of the meter movement and also hold the balance spring tie point.
How to check for this would be diassembling the movement from it's case and visually see if the pointer is in a skewed position. Another, but not always, indication would be that the pointer itself is not parallel to the scale pan. (meter face) Then again, the pointer could be touching the scale pan for some reason and then it would be a simple procedure to bend the pointer GENTLY up from the scale pan.
Here's another idea...
It could also be that the meter is in perfect condition in all respects but the meter movement barrel (the item that the M/M coil moves around) has been contaminated with microscopic, literally, bits of ferrous material which is just high enough to cause physical interference to the rotating action of the meter coil. If the action of the meter continually stops at one point on the scale, or many points, this could be your problem.
One problem I've encountered with old Hallicrafters meters is that the brass meter case will tend to split over the years allowing contamination of the meter with dust and moisture. It would've been nice if Hallicrafters used a standard fitting case that could be replaced easily but no, if you're lucky, you have to seal up the case by soldering all the splits and hope it'll fit back in place without you having fits.

Hope this loong winded disertation helps....

_________________
"Resistance may be futile but capacitance has potential"


Top
 Profile  
 
 Post subject:
PostPosted: Mar Thu 31, 2011 10:49 pm 
Member

Joined: Mar Sat 27, 2010 7:06 pm
Posts: 48
Location: Montrose, Colorado
Thanks, gentlemen, for your replies. I actually have two of the meters that need some work, and I have sent one to Byram and the other to Ram Meters, which I tracked down this morning.

I had looked over the meters pretty carefully and pretty well knew what was wrong. However, I don't have the tools and probably not the interest in doing the work myself, so off they went.

Thanks again for your replies.


Top
 Profile  
 
 Post subject:
PostPosted: Apr Sun 03, 2011 1:23 am 
New Member

Joined: Mar Wed 16, 2011 10:44 pm
Posts: 4
Location: Peekskill, NY
The trick for removing the fine bits of magnetic material
inside the meter movement is to simply unscrew and detach
the magnet from the movement.

Then blow out the debris and re-assemble.


Top
 Profile  
 
 Post subject:
PostPosted: Apr Sun 03, 2011 3:25 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 6361
Location: Freeport, LI, New York 11520
"Then blow out the debris and re-assemble."

...while not convoluting the balance springs....

_________________
"Resistance may be futile but capacitance has potential"


Top
 Profile  
 
Post New Topic Post Reply  [ 6 posts ]  Moderator: Sandy

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 7 guests



Search for:
Jump to:  



















Privacy Policy :: Powered by phpBB