[AMPS] resistors

[km1h@juno.com]

On Sun, 21 Feb 1999 08:22:49 -0800 Rich Measures <measures@vc.net>
writes:
>Carl said:
>>
>>Which is why 100K is the suggested max in any literature I have seen 
>for 
>bleeders. 
>
>€  References, please.  .  In a typical 8171 anode-supply, a 100k-ohm 
>bleeder would dissipate 810 watts.  

I suggest you read the original post which had nothing to do with your CB
tube. Neither was a single 100K bleeder mentioned in my reply since the
160W dissipation is too close for comfort in a 200W resistor, which could
lead to premature failure..

 

>
>>>>>If I wanted a Reliable bleeder for a 4kV C-filter supply, I would 
>>>>>series up 8 to 10  Matsushita/Panasonic 100k-ohm, 3w MOF resistors 
>on apiece of 
>>>>>perfboard and be done with it.  
>>>>
>>>>Absolute YUK !  800K to 1M bleders..no way Jose.
>>>>
>>>Ä  What is to be gained by using a 200k-ohm bleeder on a C-filter, 
>Carl?
>>
>>Quicker HV bleed down time, less chance of a recharge. 
>
>€  What mechanism recharges the capacitor?  


An incomplete discharge. Something very easy to do for an inexperienced
person..


>
>>  All my concerns are safety related and for others not well versed 
>in PS 
>issues.
>>
>>A string of 3W does not offer much of a voltage breakdown safety 
>margin.
>>Matsushita not a common distributor item and similar wattage 
>Panasonic,
>>etc are only 350V.  
>
>€  The manufacturer's (Panasonic/Matsushita)  rating at 70 deg. C 
>ambientis 500v or 3w .  For a 100k-ohm unit, the realizable 
>dissipation is 2.5w 
>at 500v.  .  

Lets see, what supply are you working with at this moment? The original
post or an 8171 ?  You drift around too much trying to make a point that
suits the instant.

BTW, the DigiKey catalog rates the Panasonic/Matsushita 3W at 350V, which
would put a string of 10 over the ratings in a 4KV supply and would be
insanity at 7500V.

Of course, someone recommending an 8171/4CX10000D on the ham bands ( at
least in the USA) is not exactly all there anyway.

Cheers   Carl   KM1H


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

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