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Old 18th February 2009, 01:19 AM   #2971
Variac is offline Variac  United States
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quote:
you will want to find some way to make sure that it indeed makes good contact with the heatsink rather than having a slight warp in it that would cause an airspace.

For this reason Thermal paste between the copper and Alu sink also Iwould think.

W-Fran,
I used a 6"square aluminum tube for my heatsinks on my F4. (each one is a stereo amp run balanced)
3/16" wall thickness, but 1/4" would have been better for one of the reasons we discussed here- spreading the heat! I made it the same square inches as the Pass F4's (as mentioned make sure to account for whether both sides are exposed to cool air) plus 20% and the area is plenty but some areas are only warm..I'm sure the stack configuration helps... There is a hole in the top and bottom wood plates.

The aluminum was about $120 for two of the towers. If I had it to do again I would use 1/4"instead of 3/16" walls and not make them 20% bigger than the Pass area. The current tubes are 30" tall, 24" would be fine if 1/4" thick. The cost would have been the same because the surplus place sells by the pound.

Not a particularly cheap surplus place though..

Click the image to open in full size.
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Old 18th February 2009, 02:19 AM   #2972
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Quote:
Originally posted by Variac

Click the image to open in full size.


Beautiful
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Old 18th February 2009, 02:28 AM   #2973
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I think that the content in post #2970 is incorrect regarding the voltage divider because there are other resistors than 1K and 2.6K . . .

Anyhow, the 1K is considered too big because there will be voltage drop across 1K when current flows through it.

Simplified sketch is drawn to help my poor head with a simple picture, and attached here. . .

Cheers,

>><<
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Old 18th February 2009, 02:28 AM   #2974
Variac is offline Variac  United States
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fugly!
EDIT: they are biased to 250mV across the resistor

thanks!,
Mark
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Old 18th February 2009, 08:36 AM   #2975
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Quote:
Originally posted by Variac
again steampunk
The Tower of Power.
(i'm still waiting for the petrolhead who used Hemi-D aluminum cylinder heads)

Did someone say microfins ?
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Old 18th February 2009, 12:05 PM   #2976
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I have just powered up my f5, just the PS. I am using 1.25A fuses on 230v mains. I have tried three times and the fuse blows every time.

Could this be the inrush current of the transformer? The fuse will blow when the transformer alone is connected.
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Old 18th February 2009, 12:10 PM   #2977
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Quote:
Originally posted by rhysh
I have just powered up my f5, just the PS. I am using 1.25A fuses on 230v mains. I have tried three times and the fuse blows every time.

Could this be the inrush current of the transformer? The fuse will blow when the transformer alone is connected.
Are you using a thermistor in the power supply? Are you using a slow-blow fuse? How much capacitance is in your power supply?
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Old 18th February 2009, 12:13 PM   #2978
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Quote:
Originally posted by labjr


Are you using thermistor in the power supply? Are you using a slow-blow fuse? How much capacitance is in your power supply?

No thermistor as of yet, its awaiting delivery at my supplier. Using a slow blow 1.25A fuse with 176,000uf capacitance.
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Old 18th February 2009, 12:18 PM   #2979
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Quote:
Originally posted by rhysh



No thermistor as of yet, its awaiting delivery at my supplier. Using a slow blow 1.25A fuse with 176,000uf capacitance.
Long while back, I put an on/off switch across the Live/Neutral instead of in series with the live.
Blew the fuse everytime
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Old 18th February 2009, 12:19 PM   #2980
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Thermistor is going to be a month! Does anyone have any they could sell to me?
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