[R-390] Line Level Meter

[Roy Morgan]

At 06:21 PM 8/10/2004 -0400, Bob Camp wrote:
>... More or less you have the mechanical meter movement and some wires. In 
>some cases you have a resistor or two in there.


In the case of the line level meter, there is a rectifier, too.



>The meter movement is easy to check. If it wiggles when you rock the meter 
>back and forth in your hand then the bearings and springs are ok. If it is 
>pegged hard one way or the other you may have a problem with a spring. If 
>it is sitting mid scale and not moving then it's come off of a bearing.
>
>If the movement is mechanically ok then the problem often is a broken wire 
>or a failed series resistor.  ... I suppose there are audio meters with 
>diodes in them as well. Again that should be an easy fix.

Exactly, there could be a failed rectifier.  Replacement with non-selenium 
diodes will likely cause increased deflection with the correct ac voltage 
for 0 VU.  An external resistor will cure this, unless you want to change 
any you find inside the meter.

Notes:

1) The R-390 line level meters are AC meters. They indicate 0 VU for line 
level output at the rear terminals of the radio.

2) The pictures of line level meters I have at hand do not show a zero on 
the dial markings.. only a "VU" at the place where 0 should be which is at 
the "100" of the 0-100 dial markings.

3) The meter movement is a DC mechanism. The meter case contains a 
rectifier (and presumably a resistor or two to set the correct 
calibration.)  The meter has an impedance of 3900 ohms.  (That is *not* the 
dc resistance of either the meter movement or the complete meter with 
rectifier.)

4) If your meter has luminescent markings,

DO NOT OPEN IT UP AND EAT THE INSIDES.

Roy




>The one you worry about is the meter armature winding burning up. If that 
>happens then you have a bit of a problem. Other than stuff that has been 
>really nuked (as in 10 amps does not go well through a 10 micro amp meter 
>... trust me on this one) the armature rarely is the point of failure.
>
>If you do open up the meter you may be overcome by an impulse to eat some 
>of the glow in the dark paint. Be sure to open the meter in the presence 
>of another adult incase this happens to you. Multiple reported incidences 
>of this behavior are the most likely driver in the military's long 
>standing policy of removing meters from equipment destined for 
>disposal.  Again, you have been warned ......
>
>
>         Take Care!
>
>                 Bob Camp
>                 KB8TQ
>
>
>On Aug 10, 2004, at 8:39 AM, Larry and Jody Cogan wrote:
>
>>Yesterday was an unlucky day.....found a dead line level meter on a long
>>inactive 390A.  Hoping today will be a lucky one and some lister will have a
>>meter they are willing to part with.  I do expect that it wont be cheap.  If
>>anyone can help, please reply off list.
>>
>>Thanks,
>>Larry
>>
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- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
7130 Panorama Drive, Derwood MD 20855
Home: 301-330-8828 Work: Voice: 301-975-3254,  Fax: 301-948-6213
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