200D SWR spikes when getting hot.

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Joined: Mon Feb 01, 2021 9:27 pm

200D SWR spikes when getting hot.

Postby Coniac » Mon Nov 14, 2022 4:31 pm

So I've been using my 200D and lately if i'm in a long qso I feel that the radio is getting hot and then my SWR starts to spike.

Goes from 1.3 to 3+ and the SWR protect comes on and everything. I have noticed that the fan in the radio is barely audible..

I just took apart the unit and tested the fan to straight 12v and it's blowing hard as it should but when it's in the radio all powered on its slow..
I believe there is some type of thermal sensor to make the fan ramp up speed and I feel that it might not be working.

So my question is will it overheating cause my SWR to spike up?
I also see on my 7300 waterfall the radio becoming very dirty. I starts to bleed out harmonics really bad across a large bandwidth area.

Here is another thing I had happen the other day. I sold it, shipped it out and when the person got it, it did not work. I got it back opened it up and the matching transformer next to the RF transistor had become de soldiered .
Could that have damaged the transistors?

So many things kind of going on at once here..

My next step was to look over for more cold solider joints then wire the fan to constantly run at full speed and see if I still have an issue.

Any input would be appreciated. Thank youj
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Re: 200D SWR spikes when getting hot.

Postby w-u-2-o » Mon Nov 14, 2022 8:38 pm

I can't speak to the behavior of the unit when overheating, however all of the units other than the 8000 use the external chassis as a heatsink for the main heat producers, which are the 100W RF amplifier FETs. Those FETs are mechanically attached directly to the chassis.

Because the mechanical design of these units precludes any significant movement of air internally, there is little you can do with the internal fan to improve the situation. The single best thing you can possibly do is blow some air over the exterior of the chassis where the FETs are attached.

See my web article here to learn a lot more about the thermal problems these units exhibit and how to fix them: http://wu2o.dyndns.org/wu2o_fans.html

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