[TCML] FW: [tcbouklist] FW: selecting scr/triac/mosfet for staccato on vttc

[earl rhodes <earl_1975@xxxxxxxxxxxxx>]

hi everyone
im sorry if this is again too basic for the experts to handle but i cannot find the answers im looking for by searching the net...maybe i need to  learn how to search properly but i dont usually have a problem 
but could somebody clarify the criteria for my staccato switching device
the uk list has very little or NO experience with vttc's and im getting no responses form anyone below are the posts i sent in  please could somebody clear this up for me
thanks in advance
earl/teslaspigeon

To: tcbouklist@xxxxxxxxxxxxxxx
From: earl_1975@xxxxxxxxxxxxx
Date: Sat, 29 Sep 2012 21:03:31 +0100
Subject: [tcbouklist] FW: selecting scr/triac/mosfet for staccato on vttc
















 



  


    
      
      
      

hi guys

me again !!><!!

can anybody think of a reason that a mosfet would die in staccato operation ?

ive had a good look at all the schematics and stuff and they are triacs in use not mosfets

but having said that the ratings are looking good 

a dual 833c vttc is being pulsed using a 400v 6amp triac the filament xfmr is a 20 amp job so im not seeing any reason not to try my irfp460 in my coil ...unless of course one of the experts on mosfet operation can tell me why it wouldnt work...maybe the internal diode cold cause problems 

im not sure thats why im asking 

please help...

earl



From: earl_1975@xxxxxxxxxxxxx

To: tcbouklist@xxxxxxxxxxxxxxx

Subject: selecting scr/triac/mosfet for staccato on vttc

Date: Sat, 29 Sep 2012 09:22:28 +0100



hi guys

does anybody know the criteria for my switching device for my vttc

ive managed to scrape together a staccato controller  using parts from dead boards( an audio mixer and an old telly)

the controller is fine and dandy but im unsure about my mosfet/scr/triac

does anybody have an idea about how much voltage/current were talking about

i have an irfp460 spare but thats all till i get some dosh will it do the job 

filament voltage is 12.6 volt and current is rated 20-25 amp

the irfp460 is a 500 volt 18.5 amp continuous and 73 amp pulsed mosfet which im sure most of you are familiar with

i realize its continuous rating is below  the rating of the filament but the pulsed rating is way over

also i did say i wasnt going to do it in staccato mode but i think its actually compulsary for tube lifespan extension and the single sparks are much less intimidating and more alluring than the bushy mess of 50pps

cheers guys 

earl



		 	   		   		 	   		  



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