[R-390] Mechanical filter alignment

[Bob Camp]

Hi

The reading you get will depend a lot on the ohm meter you are using. Ideally it should read above 100 meg with -10V on the line. You will have significant trouble below 10 meg.

Bob

On May 26, 2013, at 11:37 PM, Gordon <gordon at n6wk.com> wrote:

> 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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>> 
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> 
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