[R-390] R390A Audio Meter FS

[Stephen M. Murphy]

In my Motorola, the meters are definitely not the same: Line is set up 
for measuring AC and Carrier for DC. The Carrier meter cannot be used in 
the line position; it'll just bounce about the left peg.  No question... 
done it before.

I suspect that the line meter would show at least some deflection if 
wired into the carrier circuit with the correct polarity.  This is an 
educated guess, haven't tried it myself.

If I recall, the specs are different for the two meters; about 3500 Ohms 
for the Line and 17.5 for the Carrier.

Dunno if they varied over the years, but that's how mine is...

73

Steve N8NM

On 09/21/2010 03:39 PM, David Wise wrote:
> TB102 serves multiple purposes.
> CR101, between terminals 3 and 5,
> is for Diversity AGC.
> Terminals 1 and 2 let you open-circuit the
> RF GAIN control.)  Terminals 6-8 are LOCAL AUDIO.
>
> The LINE AUDIO output is actually on TB103,
> terminals 10-13.  If you go to TM11-856A
> Figure 5-13, Schematic Sheet 4 of 4,
> in regions 1A to 4C, you will see that M101
> has no polarity and (with an attenuator pad)
> is across the secondary of LINE AUDIO transformer
> T602 with no diode in sight.
>
> Dave Wise
>
>    
>> -----Original Message-----
>> From: rbethman [mailto:rbethman at comcast.net]
>> Sent: Tuesday, September 21, 2010 12:21 PM
>> To: r-390 at mailman.qth.net
>> Cc: David Wise
>> Subject: Re: [R-390] R390A Audio Meter FS
>>
>>   I suggest you go look at TB-102.
>>
>> Note the CR-xxx that is mounted there.
>>
>> I wasn't aware that anyone needed to "prove" what is in the circuit or
>> the manual.
>>
>> I simply restore these for MY purposes.  One '67 EAC and a Collins '51
>> contract from St. J's.
>>
>> Members of the list have a tendency to focus in on "small" areas, NOT
>> open their minds and eyes to the WHOLE!
>>
>> Bob - N0DGN
>>
>> On 9/21/2010 3:00 PM, David Wise wrote:
>>      
>>> Not yet.  The only place it's marked with a polarity is on the
>>> Mainframe Wiring pictorial diagram, and that's nonsense,
>>> because M101 is fed with audio AC.  That puts at least a
>>> rectifier inside, so although you can determine the FS
>>> current externally, to measure the resistance you have
>>> to bust it open.  It could be a 17-ohm movement, but
>>> you haven't proven it.  I hope it is...
>>>
>>> Dave Wise
>>> SWL in Hillsboro Oregon
>>>
>>>        
>>>> -----Original Message-----
>>>> From: r-390-bounces at mailman.qth.net
>>>> [mailto:r-390-bounces at mailman.qth.net] On Behalf Of rbethman
>>>> Sent: Tuesday, September 21, 2010 11:15 AM
>>>> To: r-390 at mailman.qth.net
>>>> Subject: Re: [R-390] R390A Audio Meter FS
>>>>
>>>>    Please pull out the TM 11-856A.
>>>>
>>>> As you go through the schematics, you'll note the BOTH
>>>>          
>> meters have a +
>>      
>>>> and a - connection.
>>>>
>>>> Keep digging and reading.....
>>>>
>>>> These are the SAME interior devices with different faces.
>>>>
>>>> Bob - N0DGN
>>>>          
>>
>>      
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