Power Loss After 7000DLE Warms Up

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W3MMR
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Power Loss After 7000DLE Warms Up

Postby W3MMR » Tue Feb 07, 2023 12:59 am

Not sure where to post this, so Scott, please move the thread if needed.

So, ive noticed that my 7000DLE (blue face, Thetis v2.9.0 x64, FW v2.1.18) is losing output power after things get warm. I mainly operate AM and noticed my carrier power is starting to drop after 3 or 4 transmissions. With the drive slider in the same position, it output 51w in tune. After it warms up, it will output 46w with the drive slider in the same position. This translates to 25w +/- of carrier loss from my amplifier. Now, the case isnt getting overly warm and im no where near the limits of the rig.

My 200D did not do this. That thing was absolutely rock solid.

Any thoughts as to what could cause this? Bias changing with heat? Overheating in the low pass filter section?

Any help would be appreciated.

Perry
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w-u-2-o
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Re: Power Loss After 7000DLE Warms Up

Postby w-u-2-o » Tue Feb 07, 2023 1:45 am

My best bet would be bias changing with increasing temperature.
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Re: Power Loss After 7000DLE Warms Up

Postby W3MMR » Tue Feb 07, 2023 2:22 pm

w-u-2-o wrote:My best bet would be bias changing with increasing temperature.


Is this a common issue with the 7000 series? Also, is there anything that can be done to stop this? Im going to add some cooling on the top of the case to see if that will stop it or at least make it less apparent.

Thanks Scott,
Perry
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w-u-2-o
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Re: Power Loss After 7000DLE Warms Up

Postby w-u-2-o » Tue Feb 07, 2023 2:42 pm

Not having a 7000 I can't say for certain.

However, given that the thermal design of the 7000 is similar to other models, I can highly recommend blowing some air over the top of the chassis.

You might find this old article I wrote valuable: http://wu2o.dyndns.org/wu2o_fans.html
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W3MMR
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Re: Power Loss After 7000DLE Warms Up

Postby W3MMR » Tue Feb 07, 2023 7:28 pm

Good article. I ran 1 fan on my 200d the entire time I had it. But not the 7000. I'll out fans on tonight and re test.
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W3MMR
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Re: Power Loss After 7000DLE Warms Up

Postby W3MMR » Wed Feb 08, 2023 5:17 pm

So last night I decided to put a fan on the right rear (looking at it from the front) of the radio. Doing 3 minutes on, 3 minutes off, of 50w carrier, I would lose 1 watt of power. By the time I would key back up after 3 minutes, the fan would cool things down and the power would be back at 50w. I haven't tried 100w to see what the power loss would be.

If it keeps becoming an issue. Even with two fans, I may contemplate breaking the radio down, putting the final board on a heatsink, mounting in a rack cabinet, pressurize the cabinet, and exhaust the air across the heatsink. I know someone who has done this and it works well.

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