No RF Power - Help

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  • Updated 3 months ago
I have a Flex 6500 running v2.5.1 and turned it on this morning and went to transmit and with the RF Power set at 100 I only get the following:  

10M: 2.1 watts 
12M : 2.2 watts
15M: 0.6 watts
17M: 0.5 watts 
30M: 0 watts

Testing above was into a dummy load (SWR 1.1) but I also tried different antennas, different bands, different modes.  I shut down the radio, computer and did a complete reboot, still the same problem.

Any help would be greatly appreciated, thanks for reading and I hope someone has a suggestion or fix.

Sincerely,
Bart
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Bart Haynes

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Posted 4 months ago

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Paul - K6HR

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Hi Bart,
You should do a reset on the radio by holding in the power button for a few seconds. The radio will reset and your TX should return. Save any profiles ahead of time just in case.
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Bart Haynes

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Paul:

I gave it try again but it did not work.  I appreciate you taking the time to respond and hopefully someone will have the solution.  Thanks again for your suggestion.  
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John - AI4FR

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Odd that all was well yesterday and then when powered on today the TX is gone. Scary! I also power cycle here. Well to go thru some obvious things that probably don't apply: make sure under radio set up that the TX power is not limited, I assume you get no strange reaction when you try to transmit such as radio shutting down due to lack of supply voltage, you've simplified things by running just one slice and are sure that you are on the correct antenna. You're using the hand mic on FM but have tried other modes. Mic profile is correct and pointing to correct input device. What the heck, if you have an ATU, try tuning into your dummy load and test again. I fear you have done much of this and a help desk ticket may be in order.
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Pat N6PAT

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@Bart,

Have you tried downgrading to 2.4.9?
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Bart Haynes

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John:

I tried the hard reset using the "OK" button and then momentarily hitting the power button, no joy.  I checked the Radio Setup power and its at 100 watts, voltage good going to radio.  I have tried CW, FT8, SSB and I'm using the Tune button and even sending CW with no joy.  I tried running the ATU and it didn't have an effect.

Thank you for your suggestions, I really do appreciate it.

Bart
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Bart Haynes

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Pat:

I have not, didn't think about it, let me give that a try....no joy, same thing, great idea though.  Thanks Pat.

Bart
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Neal - K3NC, Elmer

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Bart I did not read if you tried removing power from the back of the radio (not turnoff the power supply but remove the anderson poles count to 10 then plug them back in. Secondly, try testing with the Tune button with the tune power at 10 watts. If, (and I hope) you do get 10 watts,  then slowly increase the tune power while the tune button is depressed and verify if you can get 100w out.

If not, go to flexradio.com and create a helpdesk ticket!
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SteveM

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Bart:


Do you have anything extra connected to the back of the radio - like a lightning suppressor? If so, take it off. In fact, make sure there is only a single good-coax from the radio to the dummy - no antenna switches/amps/tuners/supressors etc.


Did you try both antenna ports on the radio?

(Edited)
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W7NGA

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Bart, when I had a 6500 it exhibited the same symptoms. The Output transistors were blown and needed replacement. Flex did a nice job of repairing and returning the 6500 in less than two weeks. Of course, there is the chance that it is something else but I suspect it is not. -W7NGA
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John - AI4FR

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W7NGA your post was my first thought as well but did not want to go down that road. But how did this happen? Bart made no mention of storms, power supply issues, operator error, etc. The radio worked perfect the night before, he shut it down, came into the shack the following day and simply turned it on. Was your experience similar? Bart did make no mention of unplugging antenna's and plugging them back in. I've seen sparks on the coax from a static discharge which is why I always ground the leads before attaching to the radio.
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W7NGA

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Just a bad batch of transistors as I recall. Flex seemed well aware of the issue. I was actually in receive mode ... heard a slight click in the speakers and could not transmit later. 
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John - AI4FR

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Thanks!! I do wonder now about the date of manufacturer for the radios that might be affected by this. I think the Palstar LA-1K amp also suffered from a similar issue with their LDMOS transistors. I've seen several instances, including personal experience, in which one would just go out. It died. In all cases they died with-in a few days of service. Once the bad LDMOS was changed out the amp became unkillable.
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Bart Haynes

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Neal:

Thank you for your suggestion, I did try unplugging the Anderson Poles for 10 seconds, I actually waited several minutes to make sure and then brought it back up as you suggested but no change in the output.

SteveM:  

Never thought of trying the other antenna port so I took your advice, sorry to say, it did not change the output.  To confirm, nothing is hooked to the back of the radio other than coax, power, speakers and Ethernet, also I am hooked directly to the dummy load and tried a watt meter in between to confirm output.

W7NGA:

I think your on to something, I suspect its something related to the output circuitry such as you described.  I went to Flex and started a Help Desk ticket, I have a feeling its about to be shipped to Flex.

John:

This is a mystery, it could of been just the time for the transistors to go.  I will reply back once I hear from Flex and after its returned with the repairs to list what it was so others can figure out a quick resolutions should it happen to them.

Thank you to all who responded and made suggestions.  I tried each one with high hopes but it didn't pan out for me, hopefully Flex will be quick on the turnaround.  Thanks again gentlemen.

Sincerely,
Bart

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Jon - KF2E

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Did you try hitting the tune button to see what the output is as Neal suggested? If tune power is set to 10 watts or above and you have zero output when you tune, it's probably a problem with the finals.
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John - AI4FR

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Thanks for the follow up Bart. It might even be a small component that failed and not the transistors. Either way we all feel for you and hope for a speedy repair. Flex is usually pretty good at turn around times.
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Bart Haynes

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FOLLOW-UP: Great news, my 6500 is on its way home and it was the Q8 and Q9 Power Transistors that failed.  Flex received the 6500 exactly two weeks ago on Friday and this Friday they are shipping it home, great customer service.  Now, even better news, depending on how you look at it, I ended up buying a 6700 last Thursday and having it overnight shipped so I could participate in the WW-Digi contest this past weekend.  Great contest and fun last weekend by the way.  

I really wanted the 6700 for two reasons, the first is its ability to do Diversity reception and using it on 160 with my different RX antennas, testing to date has proven it works well.  Combining two RX antennas that are over 1,000 feet apart and totally different designs works great for CW and even FT8, it really makes a nice package for weak signal propagation.  The second reason was the 40dB of RF Gain for 6-meters.  I presently run an LNA600 pre-amp that is made for 6-meters but it always seemed to just drive the noise floor up.  The 6700 actually keeps the noise floor close to zero and with 40dB of gain the EME signals, and E-skip for next year, should be much more productive.

Thanks again for all the suggestions and opinions, I really appreciate your time and help.

Sincerely,
Bart  
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John - AI4FR

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Thanks for the follow up Bart. It turned out to be what a lot of us feared. On the plus side you are going to love the 6700. A really amazing radio!! Lots of configurations to run it in. Have fun!!