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Old 10th February 2009, 06:43 PM   #2801
labjr is offline labjr  United States
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Peter, that is cool. Now I'm wishing a bought one more transformer for my project.
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Old 10th February 2009, 06:50 PM   #2802
rhysh is offline rhysh  United Kingdom
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Very intresting design there peter!
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Old 10th February 2009, 06:51 PM   #2803
labjr is offline labjr  United States
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Are those spacers betweeen the transistors and the heatsinks?
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Old 10th February 2009, 06:58 PM   #2804
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Those are beryllium oxide pads which are discontinued now. Mouser carries aluminum oxide pads which are similar.
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Old 10th February 2009, 07:22 PM   #2805
labjr is offline labjr  United States
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Quote:
Originally posted by Peter Daniel
Those are beryllium oxide pads which are discontinued now. Mouser carries aluminum oxide pads which are similar.
Do you use thermal grease with them ?
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Old 10th February 2009, 07:48 PM   #2806
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Yes, I do.
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“Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC
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Old 10th February 2009, 09:43 PM   #2807
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Very nice work Peter (as usual).
How do you like it compared to...........
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Old 11th February 2009, 03:15 AM   #2808
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Default F5 Heat Sink Dissipation

Ichiban - I'm dying to find out if the house burned down yet, because I'm planning on attempting the same crazy $#@* with a D-988 amp case, (see photo). The Conrad MF35-151.5 has a thermal capacity of ~ .2 degrees C / W. Using my expert photometric capabilities and scaling by fin area, the D-988 amp has about the same fin area and thermal capacity per side - so I should get the same results. According to Pass, at idle, each FET will need to dissipate ~30 watts, so your heat sink should be about 25 degrees C above ambient.

Three questions - 1) where did the temperature settle out at the FET's after a couple hours, 2) did the bias stabilize and at what current, and 3) how far apart, laterally, were your FET's, (I can't tell where the heck they are in the pictures). Also, do you think mounting them towards the bottom of the heat sink would have helped ??
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Old 11th February 2009, 03:57 AM   #2809
EUVL is offline EUVL  Europe
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Peter,

MP930 for the feedback Rs, and Riken for JFET drain ?


Patrick
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Old 11th February 2009, 04:39 AM   #2810
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I intended to use MP930 in passive filtering between caps and I though I had 0.15Rs. When I started setting bias I couldn't understand why it only went up to 1.2A and when I decided to measure power output it appeared that the amp was giving me 4W only. Then I checked the rails and they were around 5V, so I figured out the power resistors were in fact 15R not 0.15R

In feedback I have 2 x 150R Caddock MK132 per side. I use Rikens for JFET drain and in parallel with trimpot (2k7). I used those because I already had them and didn't see a reason why not give 'em a try.
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