[R-390] Mechanical filter alignment

[Gordon]

I find that if I unplug J-208 going to the RF module, the reading from 
terminal 4 to ground goes to infinity!
Seems the slight resistance (1.6 megohm) is coming from one of the caps, 
C-226, C-284,C-273,C-319 or C-297 in the RF Module from looking at the 
schematic.

73,
Gordon
N6WK



On 5/26/2013 6:19 PM, Gordon wrote:
> Thanks Miles,
>  All of the black beauties have been replaced.
> I checked from terminal 4 to ground of TB-102 and it is 1.6 megohm.
> Does that indicate a leaky by-pass cap ?
>
> Thank you.
>
> Gordon
> N6WK
>
>
> On 5/26/2013 4:30 PM, k2cby wrote:
>> You may be barking up the wrong tree so far as AGC problems are 
>> concerned.
>>
>>
>> The most likely failure mode for the AGC bus is a leaky bypass 
>> capacitor,
>> not the AGC delay capacitor C551, which is a very solid unit.
>>
>>
>> Open the jumper between terminals 3 and 4 of TB-102.  Measure the 
>> resistance
>> from Terminal 4 to ground. It should be infinity. If it isn't your 
>> problem
>> is one of the .005 uF bypass capacitors on the AGC bus.
>>
>>
>> If the resistance from Terminal 4 to ground shows open, check C543, 
>> C547 and
>> C548, all of which are "black beauties" and should be replaced in any 
>> case.
>>
>>
>> Miles B. Anderson, K2CBY
>> 16 Round Pond Lane
>> Sag Harbor, NY 11963
>> Tel.: (631) 725-4400
>>
>> Fax.: (631) 725-2223
>> e-mail: k2cby at optonline.net
>>
>>
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