Re: ALC 100 and NO TX output (AFT5M31N) LDMOS
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sorry for my google translate hihi, i'm think going to buy a scope to try to repair my x6100. Did you try to cool down the Low-Power Linear Active Thermistor with freeze. my to i believe its a firmware bug. problem can be solved with a new firmware release ! 
[Edited Message Follows]
Morning Real,
So once again I was able to observe the radio working as normal, only for it to stop.?
I have performed many measurements on the ATU. I observe each really/LPF activating correctly in respect to the band selector. There is a capacitor next to the power pin for each LPF that is easy to measure the 3.6v signal to the LPF relay.?
In my radio the LPF is selected perfectly.
I measured, inspected and confirmed as best possible that the ribbon cable is in good condition and connects to the main board.
I left the ATU and backup battery disconnected overnight.
This morning, I came to the radio and assembled it. There was NO RF power.
I worked through the bands and confirmed each LPF - all OK
I probed the RF path and noted very low uW power.
I cycled each band and noticed on 40m the RF came back!!! (see oscilloscope)
When I turned the radio over I noticed that on the 40m band I had the ATT enabled (must have been yesterday I set this and forgot)... Remember my radio came back to life when messing with the ATT some days ago?
I ran through every band, full 5W-6W power at the antenna on every band!
I turned off the ATT - I ran through every band, full 5W-6W power at the antenna on every band!
I thought maybe this is it! I fixed it!
No....
After a few cycles and TX on CW into dummy load, the RF power is gone again to zero.?
You can probe RF power on the TX relay at the point in the photo.?
I notice by now there is some warmth in the radio due to being switched on some time in RX mode and many tiny TX in CW...
Maybe a capacitor is intermittent?
Maybe the FINAL is thermally intermittent?
Maybe there is RF pre amplifier (driver) that is failing...
The ATU is ruled out in my opinion
The LPF matrix is ruled out also as it is switching perfectly and RX is noticeably good (the wrong LPF or a disconnect would kill the RX!)?
SO, I am back to Firmware corruption, or finals going on/off due to some strange instability or maybe a bad capacitor.?
I will let the radio cool all day and try again this evening and report to you.?
Thanks
Scot
I add also, that the the radio is not working, I measured the RF voltages on the GATE of the FET at ~ 213mV (0.213V) . The output from the FET was just 13mV (less than the drive to the gate) ...
When it was TX OK, the output from the FET was 6W as in the image
?
 
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