[GCARC] FTDX3000 info

Mon Jan 7 18:49:22 EST 2019

Ken,

Glad to see you are on the trail of these issues.  I know that it sucks to
have problems with a brand new radio, but this is not an unusual
occurrence.  I sometimes think that the manufacturers are convinced that
the hams who buy these radios will figure out  what is wrong with them and
then they can incorporate the fixes for them.  When I was shopping for my
TS-590, I found that the "improvements" that made the 590s into the 590sg
were actually corrections of design defects discovered by faithful Kenwood
owners like me!  I still had to crack mine open because the fans were
incredulously installed backwards!  Unreal.

Does your MFJ auto-tuner require the TX Inhibit function in order to
operate normally?  If not, i would disable that line and run it for awhile
to see how it goes.  If it never faults again, you could either leave it
that way, or hook it back up to prove that is where the fault is coming
from. You may be able to disable that function through a service menu on
the radio.

I have another theory on that quiescent current.  They have to idle them
that high in order to get them linear enough to meet FCC distortion specs
while operating from a 13V supply.  These MOSFETS are capable of Class A
operation, but they really need a higher supply voltage to deliver that
kind of performance.  I like the idea of transceivers that will run on 13.8
volts, but they really should have stayed with bi-polar transistors for
this application. Save the MOSFETS for the big fixed station rigs and put
48V power supplies in them!

I have had problems with the fan controls in several Kenwood radios, and my
fix has been to find a source of switched 13V in the rig and put a resistor
in line so that the fan runs all the time at about half speed.  In my 590,
there are 2 fans and I have them wired in series.  Coincidentally, the
location of switched 13V that I have always used is the connector for an
external auto-tuner!

I just wanted to pass these experiences along to you in case you were
tempted to think that you should have bought a Kenwood instead.  I wanted
to let you know that you very well might have had some of the very same
problems.  Thanks for sharing your experiences with the club. I am going to
appoint you the FTdx-3000 Technical Support Expert, mostly because our
President is running a new 3000 as well!  73!

Tony WA2FZB

On Mon, Jan 7, 2019 at 5:11 PM Ken Bozarth <kwbozarth at gmail.com> wrote:

> Hey gang, here is some technical info on the Yaesu FTDX3000 that is not
> obvious in their manuals. The Tuner interface connector, a mini-DIN, can
> supply up to 1.5A reliably to an external tuner. The MFJ998 has a current
> requirement of 1.5A. These ratings are always worst-case peak ratings. The
> fuse inside the FTDX3000 is a resettable Polyswitch device rated at 1.5A
> continuous hold current and a trip current of 2.9A. These devices should
> trip when subjected to over current and return to normal after the over
> stress has been fixed. So I feel safe operating the tuner with only the
> rig's power. Used in this way, there are no timing issues when turning of
> the tuner then the rig.
>
>
>
> Yaesu Service has confirmed that there has never been a theory of operation
> written for this rig. Has Yaesu ever written one for there other rigs?
>
>
>
> Yaesu Service has mentioned the signal on the Tuner interface labeled
> "TXINH" and stated that some tuners can invoke this Transmit Inhibit
> condition, but they do not know when it is used. They said it could be the
> reason for the strange "NO TX" condition I have been complaining about.
>
>
>
> Yaesu Service also confirmed that there is no thermal regulation of output
> device quiescent current (some call it idle current). Compared to older
> rigs
> using bipolar devices, the idle current in the FTDX3000 is set surprisingly
> high, at 2.5A per FET. There may be two reasons for this high quiescence,
> both of which seem valid to me. (1) With higher quiescence, linearity is
> improved, coming close to class-A. (2) All MOSFETS have a quiescent current
> at which the current is stable over a wide temperature range. The FTDX 3000
> finals are operated below this current and so, quiescence will rise with
> case temperature, but not to the point of runaway. Yaesu engineering was
> smart to see this and use it to advantage.
>
>
>
> Yaesu Service personnel I spoke with do not know in depth how the fan
> controls in the service menu work, so they advise to leave the two values
> at
> the default values. If we could get to the design group we may find out,
> but
> fat chance of that happening. I have played with the values and found that
> I
> can make the fan run faster and if I work with them some more, perhaps I
> can
> make the fan come on at a different temperature or run indefinitely.
>
>
>
> The other night during the 10m net my intermittent No-TX issue came back
> after a month of operating flawlessly  in a normal mode. I started using an
> abnormal mode (External tuner selected but with it turned off). I think I
> am
> on to something here. Back to normal for another month. Stay tuned.
>
> 73,
>
> Ken
>
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