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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 15th Apr 2022, 8:57 pm   #1
DaveG4FKI
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Join Date: Apr 2022
Location: Ampthill, Bedford, UK.
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Default Yaesu FT767GX tx issue

HI, I am trying to get a 767GX repaired for a disabled friend. The rx is working, The fault is no transmit, I am looking at the RF unit board, there does not seem to be any Tx rf being generated within the board, using a RF probe and analyser, looking at another post on here regarding receiver issues, I get the impression that it may well be a switching diode issue ? Any guidance would be appreciated.Thanks
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Old 17th Apr 2022, 9:02 pm   #2
greenkit
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Default Re: Yaesu FT767GX tx issue

No RF output at T09 could be due to the ring mixer D68. This is an ND487C2 and they do give trouble: individual diodes go open-circuit when aged. A modern replacement restored the output in my 767.
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Old 18th Apr 2022, 3:59 pm   #3
DaveG4FKI
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Default Re: Yaesu FT767GX tx issue

Hi Interesting another forum suggested the same issue. With a rf probe it is certainly looking like that it the issue. Any idea what replacement you used. I can see a ND487R1-3R from a uk company. Did you have to take the board out to replace it ? Dave.
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Old 18th Apr 2022, 9:02 pm   #4
greenkit
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Default Re: Yaesu FT767GX tx issue

Hi Dave,
I used an Avago HSMS-2829. It's smd but can be fitted easily. These appear to be no longer available from Farnell but there are some on eBay. It's best to take the RF board out of the radio: not easy in a 767 but better than a balancing act on the bench. Remove the existing mixer and an Ohm-meter check will reveal if it's bad. I did make a note in my service manual that my radio had an extra trap wired across the mixer input, a 2.2uH choke in series with 15 pF; this wasn't on the schematic.

Good luck with the repair.

Noel
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Old 6th May 2022, 3:14 pm   #5
DaveG4FKI
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Default Re: Yaesu FT767GX tx issue

I have replaced the D68 Twice, and checked all the diodes , however when I check with a spectrum analyser probe the only frequency that is being received either side of that mixer is the 2nd LO frequency of 36.8MHz
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