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I'm having the following problem with my FT-817:

1) Receives fine on all bands

2) Transmits fine on 2m and 70cm

3) Doesn't transmit at all on 160m through to 6m

4) Keying the MIC on 160m to 6m, gives me the red Tx light and I can hear the click of a relay engaging, but no power.

Questions

a) Tried all the config settings, tried a full reset, but just on the off chance I have missed something, could this be a config issue?

b) Fact that I get transmit on 2m and 70com I guess indicates no problem with the finals (?)

c) Has anyone seen this specific failure before?

d) Any hints on what it might be?

I guess if it's nothing obvious, I'll have to print out the block and circuit diagrams, plan size like Alan W2AEW, and go through the signal path.

Hoping someone can help.

Tim

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    $\begingroup$ Are you transmitting into a dummy load or an antenna? Do you know that the SWR is OK? Have you tried a different radio with the same antenna? $\endgroup$
    – rclocher3
    Commented Jan 15, 2020 at 14:47
  • $\begingroup$ Also, if the mode is SSB then keying the mike is not enough. You must also speak into the mic. $\endgroup$
    – Jean-Marie
    Commented Jan 15, 2020 at 16:57
  • $\begingroup$ For the ssb test, I set the ft817’s meter to mic output and spoke into the mic, I can see mic power level fluctuate. The swr meter gives flat swr even with a degree of mismatch. I normally operate into a small hf linear. Thinking the amp might be broken not the rig I connected another rig outputting 5w into the amp: power meter responding. $\endgroup$
    – user2555403
    Commented Jan 16, 2020 at 8:10
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    $\begingroup$ Have you looked at the Front/Rear antenna settings? HF/50 can have different setting with VHF/UHF. $\endgroup$
    – sgub
    Commented Jan 17, 2020 at 2:35
  • $\begingroup$ Hi did you ever solve this problem as I have exactly the same? $\endgroup$
    – Damian
    Commented Oct 19, 2020 at 23:52

2 Answers 2

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Tim, what you have said provides a few clues to the problem you are seeing.

Assuming that someone has not accessed the hidden menu which allows factory alignment of the radio, your problem is not a config issue. If someone has messed with the alignment settings, ignore what follows, because what to do for that is a different answer.

I'm guessing that you are deciding on whether or not the FT817 is outputting power by looking at the power meter bar graph on the FT817 screen or by looking at an external power meter. I would use an external power meter connected to a dummy load to be sure. I'm also assuming that the problem you are seeing occurs on AM, FM and SSB. If there is no TX output only on one mode, then the diagnosis given in this answer does not apply.

For a radio that doesn't have any faults, the kind of antenna you are connected to makes no difference as to whether or not the FT817 will try to output TX power. For a working radio, if the antenna is bad or missing you will still see TX power output shown on the power meter bar graph on the FT817 screen but the high SWR icon will show.

There are no menu options for the FT817 which can cause output to be present on VHF/UHF and not on HF/6m. Also, there are no options which would cause no SSB transmit audio (and seemingly no TX output power because SSB only has power when you talk) only on some bands. So if there is SSB transmit audio on VHF/UHF then the SSB audio circuitry will be working on the lower bands as well.

Additionally, the only power control for the FT817 is provided by the menu keys under the display, and this sets power for all bands from low to high but does not allow the output power to be turned down to zero or adjusted separately for individual bands.

So your problem is not being caused by incorrectly set menu options.

The FT817 has a separate output stage including final transistors for HF/6m and VHF/UHF. It seems to me that the most probable explanation for what you are seeing is that the HF/6m output stage has failed, and this is most likely (not definitely) going to be caused by a failed output FET 2Sk2975 in the HF section of the PA output module. This device can be replaced but you need a high powered soldering iron and good soldering skills as there is a large area of heat-sink around the device which makes removal difficult.

See this link http://www.ka7oei.com/FT817-finals.pdf for an explanation on how to replace FT817 finals.

If the fault isn't the HF output FET, then fault finding will become more involved and complex.

Also, the reason for a failure is another whole subject. If the FT817 does actually have a fault, I think you should try and determine why the FT817 has failed, for example transmitting using an antenna with a bad SWR, so that you can prevent a recurrence.

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  • $\begingroup$ Hi Andrew, I didn’t realise the ft817 had different finals for vhf/uhf and hf/6m. In the light of that I suspect it’s the finals. Next stage I guess is to pop the lid, and check the output from the driver stage into the finals, if I see power at that point I know it’s most likely the finals. If no power there I’ll have to work backwards. I’m not w2aew, but I’ll have a shot, guessing you’d need a matched pair of finals if indeed that’s the problem... tnx Andrew for the hints. Tim vk4qp $\endgroup$
    – user2555403
    Commented Jan 16, 2020 at 8:16
  • $\begingroup$ Tim there is only one final output FET for HF/6m so you don't have to worry about matching anything. $\endgroup$
    – Andrew
    Commented Jan 16, 2020 at 9:27
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The FT817/FT818 have a single power amplifier used from 160m-70cm, the PA is a small board with a pair of small power FETs. The board is readily available and inexpensive although that does not seem to be the problem here. As another poster mentioned it is important to ensure that you have the correct antenna port selected for that band and of course remember that SSB produces no RF output without an audio feed. Sometimes engineering menus do get corrupted values in them which can produce anomaies but I suspect this is simpler, 73 de G0FVT

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