Hi,
I've just fixed my rig with the same symptoms (Serial no begins 9J).
Just to put a fix on public record...
A key bit of info is the state of the ALC. If the ALC meter is reading
high then the ALC drive circuit is faulty - if so read on:
ALC is generated by comparing forward power, reverse power and total
current draw of the rig against thresholds controlled in the 'Hidden
Function' Menu' and OR'ing the output. You can diagnose which ALC
section is the culprit by changing the ALC menu settings in
turn, after noting original values, and seeing if the rig comes back
to life. (Safest way to do this is in CW mode, keyed by the mic - no
RF is generated but DC is running on the ALC circuit).
By changing these settings you may now have a 'working' rig and a
diagnosis and have to decide whether you want to fix it properly, or
live without the protection of whichever ALC circuit you have now
disabled in software.
In my case the fault was in the IC ALC circuit - it was overestimating
the current draw of the rig. In HF or VHF mode respectively, if I
changed Menu F11 or F12 to 256 then the ALC reading dropped and the
transmit chain came magically back to life.
I couldn't stop myself fixing it. Total rig current draw is sensed on
the PA board using half Q3009 and resistor network sensing the voltage
drop across T3004. You can probe the IC line without removing the PA
board as there is an accessible via close to J3004. In my case
IC was never dropping below 2V whereas it should have been much lower.
Turned out to be relative drift in the values of the R3041 and R3042
which are meant to be 0.1% but have no markings to prove it. Replaced
these and all came good. Less than 1 cent worth of components.
One dead end - at first I thought it was Q3009 and replaced that
first. In retrospect the easy diagnosis is to short pins 2 and 3 on
Q3009 together - if pin 1 drops to 0 then you've probably got a good
chip, so concentrate on the resistors. For interest LM358D is the
replacement I used for this chip and probably would also do for Q1060,
Q1062 and Q1065 on the main board. LM2904 is an even better match but
hard to get. Anyway, I admit it, I wasted 50 cents and a bit of time.
(If IC line is near 0 and you still have fault then you need to look
around Q1060 on the main board. That is where IC gets compared to IALC
output from processor. Luckily Q1060 is accessable on Side A.)
The PA board is not too hard to remove and DC bench test if you are
careful. You do not need to desolder any of the RF power transistors.
Remove all screws, disconnect cables and it all comes out as one unit.
You can run it up safely in isolation on DC with 13.8V to
the normal power input, and a link between pins 5 and 11 on J3004.
Need to replace heat sink goo when refitting, pay special attention -
can also take the opportunity to buff the casting where the power
transistors mount.
Scary thing is that the component drift could have been in the other
direction and silently disabled IC ALC. Wonder how much of that is
going on elsewhere in the rig...
Hope this helps, 73,
Nick VK2ZTY
Post by fraser3914Hello,,, I have FT100D which DOES receive okay on all bands but will
NOT transmit any power on any band, and I can hear the tx signal on a
local/bench receiver, the measured power output at the antenna sockets
is around 10uW... the drive level I have measured is around minus
55dBm,,if I put -10dBm up the PA modules from my signal generator I get
around 15-20Watts output so I think the PA section is working fine,