CORRECT TEMP MEASUREMENT for ZENV4?

[commstech]

How do i measure the temp of my Zen V4? I have a thermocouple to do that but question is , where do i place the probe? i had tried placing the probe in between the heatsink fins near to where the MOSTFETs are mounted and it reads 50degree celcius. However, placing the probe in direct contact on the Q1 reads a horrendous 90degree celcius. i had used silicon pads for the Mosfets -- is the high temp on the Mosfets caused by inefficient heat transfer and that's why the cool heatsink and HOT mosfets?

[Nelson Pass]

If you have a probe, put on the sink near the output devices.

If you don't have a probe, then just put your hand on the
heat sink. My standard is 5-10 seconds before you decide
to remove your hand, which is 45-50 deg C.

[Panelhead]

Originally posted by commstech
How do i measure the temp of my Zen V4? I have a thermocouple to do that but question is , where do i place the probe? i had tried placing the probe in between the heatsink fins near to where the MOSTFETs are mounted and it reads 50degree celcius. However, placing the probe in direct contact on the Q1 reads a horrendous 90degree celcius. i had used silicon pads for the Mosfets -- is the high temp on the Mosfets caused by inefficient heat transfer and that's why the cool heatsink and HOT mosfets?

The 40 degree difference between the transistor and the heatsink is high. I was not reading 90 degrees on my output transistor, current source, or the series reg. And the heatsinks were 60 - 65C.
The silicon pads do not transfer was well as mica and grease. But it is not a huge difference. I found a high conduction grease that is supposed to be 46% better than normal grease.
It is GC type 44. Seems like the 1/2 ounce jar was about 5.00 USD. This would coat a 1000 mica insulators the way I spread it.

The container says:

"Type 44 is the latest development in heat sink componds, created to meet the need for non-contaminating and more efficient thermal transfer compound. Type 44 is a non-creeping synthetic ester based compound that exhbits virtually no bleed or evaporation over a wide temperature range, even in a vacuum. Type 44 transfers 46% more efficiently than the best silicon products and 63% better than most olefin products. Type 44 is the only heat sink compound meeting Western Electric Specifications KS21343 and meets military performance MIL-C-47113."

Whether it is better than normal grease I cannot say. But in my Zen V4 the tabs on the 044's were only 10 degrees or so higher than the heatsink.

George

[Illusus]

Where'd you get the grease George?

I noticed a pretty big difference after switching to mica/grease from sil pads. I used some very thin mica sheet, much thinner than standard pads, and made my own. Also, mica pads can be split fairly easily with a razor blade or hobby knife to get them thinner, I got four out of one pad on a previous occation.

[Panelhead]

[QUOTE]Originally posted by Illusus
[B]Where'd you get the grease George?

I picked it up locally at an electronic surplus store. But do a google for "GC TYPE 44" and two online vendors come up. One has a 1 oz. tube for 8.95, Altex the other listed the 1/2 oz. jar for 6 something.
I have had mine for a while, and mounted a lot. Still looks full.

George