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Old 12th June 2013, 07:04 PM   #13101
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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?
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Old 12th June 2013, 07:14 PM   #13102
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yup
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Old 12th June 2013, 07:19 PM   #13103
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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?
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Last edited by LucasAdamson; 12th June 2013 at 07:31 PM.
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Old 12th June 2013, 07:49 PM   #13104
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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
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Old 12th June 2013, 07:52 PM   #13105
tinitus is offline tinitus  Europe
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look out for color changes(darkening)
should be ok if it keeps its natural color
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Old 12th June 2013, 08:52 PM   #13106
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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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Old 12th June 2013, 09:05 PM   #13107
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Quote:
Originally Posted by bcmbob View Post
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.
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Last edited by LucasAdamson; 12th June 2013 at 09:07 PM.
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Old 12th June 2013, 09:08 PM   #13108
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Bob- The diodes should have heatsinks.
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Old 12th June 2013, 09:13 PM   #13109
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Quote:
Originally Posted by 6L6 View Post
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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Last edited by LucasAdamson; 12th June 2013 at 09:18 PM.
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Old 12th June 2013, 09:17 PM   #13110
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Quote:
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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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