power transformer help !!!

jim · 9th January 2004, 09:53 AM

Hi All,

I have two old power transformers salvaged from a Tek 545A 'scope.
I'd like to use them for a power amp project wich uses a vacuum tube rectifier (5U4). The transformer has several 6,3V windings of wich I want to use one for the 5U4. However since a 5U4 is directly heated this would impose 450V on the heater winding wich was originally elevated up to 350V. Do you think this extra 100V could cause any problems ?

Frank Berry · 9th January 2004, 10:59 AM

The transformer will probably handle the extra 100 volts HOWEVER the 5U4 tube has a 5 volt filament as does the 5Y3, 5AR4, etc.

SHiFTY · 9th January 2004, 09:59 PM

Should be fine, as long as the winding is good for 3A or so. I have sone this with 6.3V windings before, just adding a couple of ~1ohm 5W resistors to either side of the filamet to get it down to 5V.

9th January 2004, 09:53 AM	#1
jim diyAudio Member Join Date: Jan 2002 Location: Leopoldsburg - Belgium	power transformer help !!! Hi All, I have two old power transformers salvaged from a Tek 545A 'scope. I'd like to use them for a power amp project wich uses a vacuum tube rectifier (5U4). The transformer has several 6,3V windings of wich I want to use one for the 5U4. However since a 5U4 is directly heated this would impose 450V on the heater winding wich was originally elevated up to 350V. Do you think this extra 100V could cause any problems ?

9th January 2004, 10:59 AM	#2
Frank Berry diyAudio Member Join Date: Sep 2003 Location: Midland, Michigan	The transformer will probably handle the extra 100 volts HOWEVER the 5U4 tube has a 5 volt filament as does the 5Y3, 5AR4, etc. __________________ Frank

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9th January 2004, 09:59 PM	#3
SHiFTY diyAudio Member Join Date: Jul 2002 Location: New Zealand	Should be fine, as long as the winding is good for 3A or so. I have sone this with 6.3V windings before, just adding a couple of ~1ohm 5W resistors to either side of the filamet to get it down to 5V.