Mosfets for Tubelab SE? - Page 5

sureshm · 11th November 2011, 12:36 PM

Are the 500V Cornell Dubilier 380LX any good for the Simple SE? They are 85C so wondering if they are reliable?

tubelab.com · 11th November 2011, 12:50 PM

Are the 500V Cornell Dubilier 380LX any good for the Simple SE?I bought some and stuffed them in an SSE board. They seem to work OK but I haven't used the amp enough to judge reliability. I would guess that they will be OK if you mount the caps on the back of the board to avoid radiant heat from the output tubes.

Newark (Farnell) now has some 105C rated Nichicons. I just got 10 of them but haven't tested them yet.

rknize · 11th November 2011, 02:50 PM

Also, the area around the rectifier runs a little hotter on the TSE than the SSE, due to some additional power resistors (particularly R6).

jrenkin · 3rd January 2012, 06:30 PM

Quote:

Originally Posted by boywonder

A related question for mostly educational reasons.......In a Tubelab SE (or similar source follower application) if the rectified off load voltage of the transformer is greater than 500V, is that a problem for 500V rated parts such as the 2SK3563?

Any thoughts on this?

boywonder · 3rd January 2012, 06:43 PM

If I had to re-phrase the question today....

If the mosfet drain-source voltage rating is 500V, what prevents that spec from being exceeded (especially at startup) in the circuit? It seems that with 300B's the source voltage is as negative as -300 volts or more, not considering the + voltage on the drain.

Still wondering myself.........

rknize · 3rd January 2012, 07:10 PM

The MOSFET will never see that. The gate is derived from B-. So as B- comes up, gate voltage is applied, current flows through R14 causing a drop there that is proportional.

cddeluca · 14th January 2012, 02:07 PM

Found this device:
FQH8N100C Fairchild Semiconductor MOSFET

It's a 1000V, N-channel with a Crss of essentially zero above a Vds of 10V. Seems ideal?

11th November 2011, 12:50 PM	#42
tubelab.com diyAudio Member Join Date: Jul 2005 Location: South Florida	Are the 500V Cornell Dubilier 380LX any good for the Simple SE?I bought some and stuffed them in an SSE board. They seem to work OK but I haven't used the amp enough to judge reliability. I would guess that they will be OK if you mount the caps on the back of the board to avoid radiant heat from the output tubes. Newark (Farnell) now has some 105C rated Nichicons. I just got 10 of them but haven't tested them yet. __________________ Too much power is almost enough! Turn it up till it explodes - then back up just a little.

11th November 2011, 02:50 PM	#43
rknize diyAudio Member Join Date: Feb 2009 Location: Chicagoland	Also, the area around the rectifier runs a little hotter on the TSE than the SSE, due to some additional power resistors (particularly R6). __________________ Russ http://www.knizefamily.net/russ/cate...ics/tubeaudio/

3rd January 2012, 06:43 PM	#45
boywonder diyAudio Member Join Date: Jan 2008 Location: So.Cal.	What he said........ If I had to re-phrase the question today.... If the mosfet drain-source voltage rating is 500V, what prevents that spec from being exceeded (especially at startup) in the circuit? It seems that with 300B's the source voltage is as negative as -300 volts or more, not considering the + voltage on the drain. Still wondering myself.........

3rd January 2012, 07:10 PM	#46
rknize diyAudio Member Join Date: Feb 2009 Location: Chicagoland	The MOSFET will never see that. The gate is derived from B-. So as B- comes up, gate voltage is applied, current flows through R14 causing a drop there that is proportional. __________________ Russ http://www.knizefamily.net/russ/cate...ics/tubeaudio/

14th January 2012, 02:07 PM	#47
cddeluca diyAudio Member Join Date: May 2009	Possible substitute? Found this device: FQH8N100C Fairchild Semiconductor MOSFET It's a 1000V, N-channel with a Crss of essentially zero above a Vds of 10V. Seems ideal?

11th November 2011, 12:36 PM	#41
sureshm diyAudio Member Join Date: Sep 2007	Are the 500V Cornell Dubilier 380LX any good for the Simple SE? They are 85C so wondering if they are reliable?

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