[Swan] Sensitivity and meter on 500

[Jeff]

Thanks Steve .

I have a copy of the 4.0 compendium.  It's proven invaluable in the 350, 
400, and two 500Cs that I've rebuilt.

I'm having a look at the IF and AGC bus.  I've replaced a few of the 2 
watt and 1 watt resistors, even though they tested OK cold. I bought 
triple the requirements for the 500C, so I figured I'd give it a try 
since I've got the components.

I'm pretty sure I've got a leaky cap on the AGC as someone suggested.  
Now it's a needle in a haystack though.

Jeff



On 7/4/2017 1:30 PM, Steve Sutfin wrote:
> Jeff, I just realized that I should have said the 2nd IF was a 12BA6, 
> not 12BE6. Bit of an eyesight problem.
> 73,
> Steve k7dna
>
> On Jul 3, 2017, at 11:43 AM, Jeff wrote:
>
>> Thanks Steve!
>>
>> C202 has been replaced by discrete caps under the chassis, so that 
>> should rule out one.  I'll replace the 12BE6 as you suggest.
>>
>> I've also removed the grid, plate and load variables and sent them to 
>> the dishwasher.  I'm getting intermittent faults with them, so might 
>> be another variable.
>>
>>
>> Jeff
>>
>>
>>
>> On 7/3/2017 2:29 PM, Steve Sutfin wrote:
>>> Hi Jeff,
>>>  This is in case my response didn't get thru the 1st time.
>>> Both the 12BE6 2nd IF and the C202 CanCap have an effect on the 
>>> S-Meter AND the AGC system which could result in low receiver 
>>> sensitivity. I can see that happening with the 12BE6 after warm up. 
>>> Something to look into.
>>> 73,
>>> Steve k7dna
>>>
>>> On Jul 3, 2017, at 7:11 AM, Jeff wrote:
>>>
>>>> Hi all -
>>>>
>>>> Seeking some advice on a 500.  This seems temperature related, and 
>>>> I'm having a hard time tracking it down.  I picked up a basket 
>>>> case, and have been slowly rebuilding it.  I have it transmitting 
>>>> and receiving OK now, but only when it's cold.
>>>>
>>>> From a cold start, the s-meter and receive function works as 
>>>> expected, with good meter swings on signal peaks.  However, as the 
>>>> rig heats up, the s-meter deflects less and less until it basically 
>>>> remains stationary.  I also begin to lose receive sensitivity.  
>>>> Compressed air blown at spots underneath the chassis doesn't seem t 
>>>> have any effect, nor does air applied to the air variables.  It 
>>>> just... dies out.
>>>>
>>>> Short of just starting to shotgun everything, does anyone have any 
>>>> suggestions on where to start looking?
>>>>
>>>> Thanks...
>>>>
>>>> Jeff
>>>>
>>>> WB3JIH
>>>>
>>>>
>>>> ______________________________________________________________
>>>> Swan mailing list
>>>> Home: http://mailman.qth.net/mailman/listinfo/swan
>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>> Post: mailto:Swan at mailman.qth.net
>>>>
>>>> This list hosted by: http://www.qsl.net
>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>
>>> ______________________________________________________________
>>> Swan mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/swan
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:Swan at mailman.qth.net
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>
>> ______________________________________________________________
>> Swan mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/swan
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Swan at mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>
> ______________________________________________________________
> Swan mailing list
> Home: http://mailman.qth.net/mailman/listinfo/swan
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Swan at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html