[AMPS] TL-922 Filament Transformer Protection

[Rich Measures]

>
>Rich Measures wrote:
>>>Rich says:
>>>
>>>      > However, when R-sup fails on 15m, 20m, 40m or 80m, 
>>>      >there is seemingly no way that enough fundamental potential could be 
>>>      >developed across L-sup to damage R-sup.  
>>>
>>>If the
>>>resistor has to be derated because the ambient is 80 deg C, then even the
>>>lower dissipation on the lower bands may well be enough to 'cook' it.
>>
>>€  the R-sups in the 922 receive cool forced air and they are virtually 
>>HF-shorted by silver straps.  Does it seem likely that lower-band RF 
>>could damage these resistors?  
>
>This brings us back to the old problem that we never know the condition
>of the resistor (and/or tube) immediately before it failed. Was it still
>like new, or had it already deteriorated way out of specification? Just
>because the component finally failed on 80m, it doesn't mean that all
>the damage was done on that band.
>
€  An intermittent push-push vhf parasite is typically so brief that it 
causes no external damage to R-sup.  Instead, the damage is internal, 
and, as such, can only be discovered with an ohmmeter.   However, damage 
from 10m fundamental energy always causes visible damage.  

-  cheers, Ian.  


Rich...

R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures  


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