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Re: Blowing MMC bleed resistors...




Hi Terry,                                                             
                                                                      
I was a bit surprised myself. The resistors I have are just normal    
carbon film 1/2W units. Nothing special about them. I got them from a 
local surplus place before I found out Digikey had a better price. :( 
I didn't try ohming them, I'll test them tonight and see if there are 
any with the wrong value.                                             
                                                                      
I didn't have any problem with the ones on my 6" coil, and it has more
runtime on it. Those were the last thing I expected to fail on the    
coil. There are no metal objects near the MMC that could draw an arc. 
And when I watched one go it didn't arc to anything, it just blasted a
hole in the side and spit carbon arround.                             
                                                                      
Interestingly, it only happened for a while. I replaced them and now  
it seems to be OK. I ran the coil quite a bit after that and didn't   
blow any more. I suspected that I may have gotten a few bad resistors 
or incorrect values in there. I would be interested in trying some of 
yours and letting you test the ones I have. I expect it's just bad    
resistors. Would be nice to know for sure what's up.                  
                                                                      
Travis                                                                
                                                                      
                                                                      
                                                                      
> Original poster: Terry Fritz <twftesla-at-uswest-dot-net>                  
>                                                                     
> Hi Travis,                                                          
>                                                                     
> 	Wow!  This is a new one.  I have never heard of a bleed resistor   
failing                                                               
> and I have done testing on the YAGEO ones which suggest they are    
very tough                                                            
> indeed.  My first thought would be to check them with on ohmmeter to
be                                                                    
> sure they are not 1.2 Meg or something like that (check all of them 
in the                                                                
> string).  Make sure there are no metal objects near them the draw   
arcs.                                                                 
> Either they are the wrong value are there is something about the    
particular                                                            
> resistors you have that is not suited for the high voltage.  I still
have                                                                  
> some of the ones I use so I could send you some you could try.  I   
know the                                                              
> YAGEOs work fine.  Let me know if you want to try them and maybe    
send me                                                               
> some of yours to test if you really think the resistors themselves  
are the                                                               
> problem.