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Old 2nd February 2011, 09:57 AM   #191
JBdV is offline JBdV  Netherlands
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I guess 8 W of heat just "dissapears" on such a big metal bottom plate.
Its a sign that the (9)240's are making great thermal contact.

Measuring locally with a "temp gun" could reveal whats really happening

@Ram, why didn't you put the toroid together with the other stuff in one enclosure?

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Old 2nd February 2011, 10:52 AM   #192
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Originally Posted by JBdV View Post
Its a sign that the (9)240's are making great thermal contact.
NO !!!!
The exact opposite.
Bad thermal conductance will give what appears as a cooler running heatsink, while the devices are burning up inside.

A cool device is a good clue to good thermal conductance.
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Old 2nd February 2011, 11:16 AM   #193
JBdV is offline JBdV  Netherlands
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I don't think a (9)240 can be cold on the outside while they are burning on the inside at the same time.

Ram reported everything to be cool, so I assume his (9)240 are cool on the outside as well.

"A cool device is a good clue to good thermal conductance". I fully agree with that.


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Old 2nd February 2011, 11:37 AM   #194
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Originally Posted by JBdV View Post
I don't think a (9)240 can be cold on the outside while they are burning on the inside at the same time.
an example of a bad thermal conductor to a device with air between it and the heatsink.
remove all the bolts holding the CCS devices to the base plate. Lift them ever so slightly from touching the base plate.

Do you think the case will be cold and the devices burning hot on the inside?

It's an extreme example but it shows why a cool or cold heatsink cannot be used to determine whether a device has adequate cooling.
It's the device temperature (Tc) that matters.
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Old 2nd February 2011, 12:42 PM   #195
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Quote:
Originally Posted by AndrewT View Post
Hi Ram,
looks fantastic. Be proud and enjoy.

I am surprised at your remark "cold".
Using a 15+15Vac transformer and 200mA CCS there is some 8W of dissipation. That should not feel cold.
Maybe this aluminum chassis in more than enough for dissipate the heat (My "cold" is below 25șC), I'm using a 12+12Vac transformer.

The mosfets are as cold as the chassis (finger test)
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Old 2nd February 2011, 12:52 PM   #196
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Old 2nd February 2011, 01:01 PM   #197
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ramallo, It is a nice build that serves as a guide for many of us.
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Old 2nd February 2011, 01:45 PM   #198
AndrewT is offline AndrewT  Scotland
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I'm using a 12+12Vac transformer.
What is the voltage drop across the CCS mosFET Drain to Source?
How low will that Vdrop go if mains is at minimum tolerance?
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Old 2nd February 2011, 02:04 PM   #199
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Quote:
Originally Posted by AndrewT View Post
What is the voltage drop across the CCS mosFET Drain to Source?
How low will that Vdrop go if mains is at minimum tolerance?
I'll measure tomorrow the voltage drop on the mosfets.

The voltage drop on the resistors:

Mezmerize DCB1 Building Thread

Now is down a bit 1.49V and 7,4 Ohm of measured resistance on both sides (The two 16 Ohm resistors in parallel), the offset remains the same.

I'll try with the variac down a 10% the mains for see (My regular AC is 230V).

Last edited by ramallo; 2nd February 2011 at 02:09 PM.
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Old 2nd February 2011, 02:05 PM   #200
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ramallo, It is a nice build that serves as a guide for many of us.
Thanks Ed, have your leds inside
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