I have a couple of older FT-101Zd rigs here.
I'm not too sure how closely related the FT-901
and FT-101zd are, but I know they were in production about
the same time. First off I'd call up Yaesu and see if you can get a
manual for that rig. They may still have it, that's a good start.
Second I can't be 100% sure on this, but it almost sounds to me like
your front end may be burned out. Usually a severe decrease
front end sensitivity will be the RF transistor or in this case an FET.
At least that may be in part your problem? I only bring this up because
they used FET's type 3SK40, 3SK51 and others are easily blown out
in an high RF environment. I'm not sure if that would cause the S9 -
that you are hearing, hopefully no one has gone into the rig and tried
turning things up which can often be the case if you have bought the
rig from a Citizens Band operator.
The S9 white noise has got me stumped for the moment, but I would
at least start with a new front end FET and try to find yourself a
I know it's not much, but maybe it's a start.
> From: "David" <firstname.lastname@example.org>
> To: <Yaesu@contesting.com>
> Date: Tue, 12 Nov 2002 19:33:41 -0500
> Subject: [Yaesu] FT901 Noise
> Hello and thanks for reading I have a FT-901DM With some sort of
> self =
> generated noise.
> To be more specific the transmit works the recieve works, So long as
> you =
> recieve a signal That
> Is over S9. constant. And of course no antenna hooked up With the
> lack =
> of a better description I would have to say a white noise of sorts.
> I =
> tried bypassing the vfo for the outboard vfo but it is still there.
> My problem I guess is were do I start on trynig to troubleshoot this
> problem. I do not have a service manual but do have th schematic for
> it. =
> Also I did remove the cards and clean the edge connectors, to no
> avail. =
> The S Meter reads S9 with the white noise and I do not hear any kind
> of =
> Hum just white noise and a signal that does not exist.
> Thanks David KR4OW