[Central-Electronics] The Case of the 100V Audio Filter

[Curt Nixon]

WOnder if you have monitored the output of the filter in situ while it 
is operating?  Might tell you something.

I like the socket possibility also.

Curt
KU8L

On 1/5/2021 3:03 PM, JAMES D COMSTOCK wrote:
>   Last time I had a similar problem with my 100v I gave up and completely rebuilt the filter with all new components. It worked for a while.
>   Eventually I ended up running a tiny steel brush through the socket connectors and cleaned, tightened and re-soldered all the connections. The problem has not returned. If it does I will replace the socket.   Jim K0jjf
>
>
>
>> On 01/05/2021 10:47 AM Robert Nickels <ranickels at gmail.com> wrote:
>>
>>   
>> I can toss out a mystery for the group to ponder:
>>
>> I've been trying to find the reason why the output power of my 100V is
>> low.  Sometimes it would start out OK at 100 watts but then dropped to
>> 60 watts or less a half hour or so later.
>>
>> I've narrowed the problem to the Audio Filter module but it's puzzling
>> because I can't find anything wrong with it.    If I bypass it by
>> jumpering  pin 2-5 so the phasing system is driven directly from the
>> output of the Audio Limiter module, I can get full 100 watt output with
>> 2.25 volts peak-to-peak out of the limiter.    The output of the filter
>> is about 1/2 that level and the waveform becomes distorted as audio
>> level is increased.   If I adjust the audio input to provide that same
>> 2.25 volts out of the limiter with the filter in place the transmitter
>> power output is only 30 watts.   Even if I increase the audio level
>> greatly the output never gets to 100 watts.
>>
>> This makes it seem that the Audio Filter is defective, but I've run the
>> module on the bench for hours, sweeping from 100 to 5000 Hz and it works
>> perfectly.    The voltages in the transmitter are correct (6.5VAC fils
>> and 315 VDC) but instead of the nice sine waves and consistent output
>> within the filter bandpass I see on the bench, the output becomes
>> distorted and triangle wave shaped as the level is increased, and will
>> not drive the transmitter to full output even then.
>>
>> The next stage in the 100V is the phase inverter which presents high
>> impedances so it can't be a loading effect, besides the limiter will
>> drive this stage just fine.
>>
>> I'd like to have the audio filter inline but am getting nowhere in
>> figuring out why it works on the bench but not in the transmitter and am
>> about ready to bypass it and call it good. Wonder if anyone has run into
>> this mystery before or has any suggestions?
>>
>> 73, Bob W9RAN
>>
>> ______________________________________________________________
>> Central-Electronics mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/central-electronics
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Central-Electronics at mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
> ______________________________________________________________
> Central-Electronics mailing list
> Home: http://mailman.qth.net/mailman/listinfo/central-electronics
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Central-Electronics at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html


-- 
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus