Hermes output power down

[gil pita]

My trusty Hermes Lite just dropped power half way. 

Checked all the obvious, antenna, connections etc. Hooked to a dummy load where it was reading 5-6 watts it's now 2.5 to 3 watts using Thetis. No changes have been done to the software since I started using it about 8 months ago. No overheating issues and I use it for CW mostly.

Anything I should look at before concentrating on output finals?

Gil 

[Dan Cusick]

Inspect the output transistors.  Did one get knocked off?  What about the jumpers and caps around them.  Has it been in the case or is it out.   I had the same problem and i had knocked a jumper & cap off the board.

73,

Dan

W9IRL

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[gil pita]

Thanks for the reply. It has been in the case since I got it used many months ago, no mods no issues, just all of the sudden notice the power down about 50%

I'll have to go in and check what you mentioned as a start.

Thank you

[Mike Lewis]

It is worth checking the PA settings in your SDR app. 

 

You did not specify what SDR app and version you were using, and possibly the output change occurred along with an app upgrade where it may have reset some settings.

 

Also check the power on every band in case the filter board has an issue on 1 of them.

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[gil pita]

I have been using Thetis V2.10.3.13 x 64 since February without any changes. All bands have low power out.

I do have other versions of Thetis downloaded and the SDR Console I can try out later today. Not too hopeful since this happened suddenly in the middle of a QSO.

Gil

[gil pita]

Took some time to check further... the power actually fluctuates from 3 up to about 5.5 watts on a dead key for a few seconds. At times it will settle at 5.5w then suddenly drop to 2.5w - 3w.

The obvious has been already checked, jumper cable going to the tuner, different antenna, dummy load, different power supplies. Temperature does not go any higher than 41C while transmitting on CW, which is the only mode I have used so far with this Hermes. 

Not sure where to go from here other than reflow solder joints in the location of the finals, for now. 

[gil pita]

After close inspection, magnified XXX, man this stuff is small! I noticed one of the finals, #1 pin (gate I believe) had a bad/cold solder joint, I carefully reflowed with new solder and done. 

A steady 5 to 6 watts depending on the band.

Now, here is the kicker, whoever put this Hermes together decided super glue was the way to go installing the heatsink to the board!! 

This was IMO interrupting the flow from the board to the heatsink therefore overheating the finals and possibly causing this problem in the first place. Took me a little while with some acetone to pull the sink off the board without damage. Cleaned both the board and the heatsink, applied thermal paste and good to go.

Running cooler and good steady output now.

I hope you guys found this topic interesting and hoping it could possibly help someone in the future. 

[Steve Haynal]

Glad you solved your problem!

73,

Steve

kf7o

[gil pita]

Steve, thank you. Though I don't think a similar topic had been posted, I have learned quite a bit from reading general postings in this group.

Best regards

Gil