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 12th June 2013, 07:04 PM #13101 LucasAdamson   diyAudio Member     Join Date: Feb 2009 So, my F5 is built and working beautifully! The amp is velvety silent and sounds great! One thing that concerns me - everything is a lovely cool temperature, except the heat-sinks of course, which I can touch for an indefinite time, and even the mosfets I can touch for as long as I like, BUT, the bias resistors, the 3W 0.47R Panasonics, raised off the board to aid cooling, are as hot as hell to the touch. Is this normal? __________________ Lucas
 12th June 2013, 07:14 PM #13102 Zen Mod   Official Court Jester diyAudio Member     Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain yup __________________ my Papa is smarter than your Nelson ! clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa...© by Mighty ZM
 12th June 2013, 07:19 PM #13103 LucasAdamson   diyAudio Member     Join Date: Feb 2009 Thanks ZenMod. Is 3W a bit of a mistake then? Wouldn't it be better to parallel up two 1R 3 watters to make a 6w .5R? __________________ Lucas Last edited by LucasAdamson; 12th June 2013 at 07:31 PM.
 12th June 2013, 07:49 PM #13104 Zen Mod   Official Court Jester diyAudio Member     Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain P= I^2 x R [W,A,Ohm] if dissipation is under 50% of resistor rating , I'm calling it idiot proof with Iq of 2A , P= 2^2 x 0R47= 1W88 , not exactly idiot , but still bullet proof __________________ my Papa is smarter than your Nelson ! clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa...© by Mighty ZM
 12th June 2013, 07:52 PM #13105 tinitus   diyAudio Moderator R.I.P.   Join Date: Nov 2005 look out for color changes(darkening) should be ok if it keeps its natural color
bcmbob
diyAudio Member

Join Date: Dec 2009
Location: Bay City, Michigan
Speaking of heat, I managed to get my Peter Daniels PS where I can detect the temps. The rectifiers are blazing and the resistors are way above ambient. I hadn't noticed that on earlier configurations. Anything out of order here?
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Bob M.
"Arrange Whatever Pieces Come Your Way."

diyAudio Member

Join Date: Feb 2009
Quote:
 Originally Posted by bcmbob Speaking of heat, I managed to get my Peter Daniels PS where I can detect the temps. The rectifiers are blazing and the resistors are way above ambient. I hadn't noticed that on earlier configurations. Anything out of order here?
My rectifiers are perfectly luke warm. I am using ST BYW99W200 diodes - well over rated and superb specs. Recommended, if you need to upgrade! Nelson Pass likes them too, so you'd be in good company.
__________________
Lucas

Last edited by LucasAdamson; 12th June 2013 at 09:07 PM.

 12th June 2013, 09:08 PM #13108 6L6   diyAudio Moderator     Join Date: Oct 2010 Location: Denver, Colorado Bob- The diodes should have heatsinks. __________________ Illustrated Build Guides - Pass F4 - Pass B1 - Pass F5 - Pearl 2 - O2 HPA - Hagerman Bugle 2 - Pass Aleph J - Me at BA '13 -Pass F5Turbo - BA-3 Amp - BA-3 Preamp - F6 AmpCampAmp
diyAudio Member

Join Date: Feb 2009
Quote:
 Originally Posted by 6L6 Bob- The diodes should have heatsinks.
Yes indeed, you do need sinks - direct connection to 3mm aluminium casing is sufficient, but mica washers and goop required if you do down that road. Big Chief individual sinks are also good, and have intrinsic electrical isolation (unless they touch each other). Are those MUR 820 diodes? Are they under-rated? Are those resistors 3w or greater? They aren't the recommended Panasonic metal film ones, but maybe that's not important. I find that soldering them away from the PCB helps cooling potential considerably.
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Lucas

Last edited by LucasAdamson; 12th June 2013 at 09:18 PM.

bcmbob
diyAudio Member

Join Date: Dec 2009
Location: Bay City, Michigan
Quote:
 Originally Posted by 6L6 Bob- The diodes should have heatsinks.
O.K., I'll put some on. I'm using Fairchild Stealth. Should those mentioned above be considered an upgrade?
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Bob M.
"Arrange Whatever Pieces Come Your Way."

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