[Moon-net] New photos of 2m-8877

[Jean-marc BORD]

LANCE COLLISTER a écrit :
> Edward Cole wrote:
>   
>> Just posted some new photos of the 8877 project.
>> http://www.kl7uw.com/2m-8877.htm
>>
>> How long a time delay needed for 8877 filament inrush current 
>> limitation?  I can get maybe ten seconds using a RC time constant 
>> timing ckt. controlling relay with 100-ohm resistor to load inrush to 
>> filament transformer.  That should lower filament to 3.0 volts at 11 
>> amps.  I'll be running 4.9 volts after startup.
>> For pretuning the 8877, what resistor value to use across 
>> cathode-grid (using MFJ-269).  Can I also pretune output ckts this 
>> way and what resistor value for anode-grid?
>>
>> *****************************************************
>> 73, Ed - KL7UW              BP40iq, 6m - 3cm
>> 144-EME: FT-847, mgf-1801, 4x-xp20, 185w
>> http://www.kl7uw.com     AK VHF-Up Group
>> NA Rep. for DUBUS: dubususa at hotmail.com
>> ***************************************************** 
>>
>>
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>>
>>     
> Hello Ed,
>
>  From what I have read, the most critical time for filament warmup is the first 
> few AC CYCLES before the filament has time to warm up at all.  I have used 4 or 5 
> seconds delay before going to full filament voltage only because I figured it 
> would be better to be safe than sorry.  After 4 or 5 seconds, you can see the 
> voltage stabilize at the lower current, meaning the filament has definitely begun 
> warming up.  GL and VY 73, Lance
>
>   
On my 8877 PA I have a resistor in serie which limits the inrush current 
(few 0.x ohms) which I left always in the heating circuit. You just need 
a tranformer which is designed to provide 6v+ac
If you need more details, please ask.

Kind regards
Jean-marc F1HDI