R100 heat sink temperatures

mheusser · Post by **mheusser** » Sun Apr 30, 2006 10:41 am

I have an R100 that will be used as an Amateur Radio Repeater. I have been testing this unit for the past few days and have noticed that the Heat sink gets very warm in just a few minutes (about 10 min). I am guessing that the duty cycle has been about 50%. My question is, does this sound normal for an R100 unit with the transmitt power set to 25 watts?

Thanks,

Mike

Rayjk110 · Post by **Rayjk110** » Sun Apr 30, 2006 11:26 am

I personally would run a fan on it, that activates via heat sensor, as does the GR300. My highschool's R100 has ran without a fan on it ever since they got it (Circa 1996) and it's been fine. But if it's going to be on amateur with more use, I would recommend a fan.

Now, in the 10 minutes you described, was the unit active in TX?

Or was it idiling in standby? (Not TX'ing)

mheusser · Post by **mheusser** » Sun Apr 30, 2006 12:26 pm

I was transmitting into a dummy load for about 5 out of the ten minutes.

It seems really warm compared to other repeaters we have in service. Also, when I bought this unit, there was a trace burned off of the power supply board next to the xmit PA. It supplies the xmit 13 volt B+. I am wondering if I should dig deeper and and confirm the xmit current is ok.

Mike

Rayjk110 · Post by **Rayjk110** » Sun Apr 30, 2006 12:57 pm

Well, transmitting on most of anything for 5 minutes straight will make it pretty warm. I'd say it's probably going to be OK, but again, I would recommend running a fan on it if it's going to be a primary repeater,

Post by **harrisjt2000** » Sun Apr 30, 2006 1:14 pm

I'd deffantly would put a fan on it

My highschool's R100 has ran without a fan on it

lol, one of the high schools in the district I work for (also the high school I went to) but, the repeater set up there is two maxon mobiles with an off brand rick. The whole setup is in an almost water tight box with no vents or any fans on the radios or power supply and the box is mounted on the top of the tower. they paid around 7 grand for this set up and it hasn’t failed yet(luck I guess) I didn’t know this high school had a repeater till i had to climb the tower to fix the microwave link back to the county office

mheusser · Post by **mheusser** » Sun Apr 30, 2006 1:20 pm

Thanks Ray,

This will be used cross band (VHF and UHF) and I would expect that it will have a very high duty cycle some days of the week. It sounds like these run really warm and I don't need to worry about. It will be in a fairly controlled environment with temps around 70 degrees F.

Mike

Will · Post by **Will** » Sun Apr 30, 2006 9:55 pm

One important point, the R100 is designed to mount on a wall with the heatsink to the right and vertical.

Most of the heat comes from the two regulator pass transistors. 50 to 70 watts of heat in just the two pass transistors. On one we mounted them on a seperate heatsink on the other side.

You should look at the heatsink thermal compound, white junk, used between the two regulator pass transistors and the heatsink. The 'grease' dries out and becomes a poor heat conductor. Most will clean off the white junk and use the clear silicone grease, it is more suited to the mica insulators.

Also check the 'grease' on the PA to heatsink, clean off the old and replace with new Wakefield/3M (white) heatsink compound.

mheusser · Post by **mheusser** » Mon May 01, 2006 7:28 pm

Thanks Will. I am going to do as you suggest.

Mike