Thanks, Carol-
Interesting piece of detective work!
I have heard that some of the Hi-K (high dielectric constant)
monolithic ceramic capacitors can be microphonic. So a
little bypass or coupling cap could be the source of this odd
modulation. If so, you could eventually track it down and
replace with a type not known for microphonics. Using
some small electrical hand tool that can produce vibration
only (no rotation), touch it to suspected components
while transmitting. I bet the modulation gets louder the
closer you get to the right cap. (Watch out to not
accidentally ground any live points in your circuit)
Your tape fix will probably do just as well, and is a lot easier
than completely tracking down and isolating the culprit.
The only suggestion I might make is to go and look for
some of that closed-cell foam packing material. It usually
comes in fairly thin white or pink sheets. It has a slightly
slippery, rubbery texture. That stuff should hold up a
little better over the long run- it is surprisingly tough. It
normally gets used as a wrap for shipping fragile items.
There are a few slightly different types. The best one is
the one that is shiniest. It is very tough and puncture
resistant. It should outperform that tape.
73, David K3KY
To: yaesu@contesting.com
Date sent: Mon, 26 May 2003 19:59:43 +0100
From: Carol L Maher <w4clm.ham@juno.com>
Subject: [Yaesu] FT-3000M Fan noise in Xmit
> Hey guys,
> I thought I would pass this along just incase any of you have one of
> these
> 2 meter Jewels. The FT-3000M 2 meter transceiver expensive (70w)
> rig just a few years ago. I bought one last year from AES on close out
> and installed it in my car. Although two meters is not my band of
> choice,
> I can only assume that most of us have a couple of these around the shack
> and one in the car.
>
> After a using the mobile rig a while I decided I really liked this
> transceiver
> and the 70 watts gives it one heck of a punch, considering that it wasn't
> too
> long ago that one had to buy and external power amplifier to get this
> kind
> of power out of their 2 meter set up in the car.
> In fact I thought I would simplify my life and try and buy
> another similar rig along with the programming software and cable then
> put it in
> the ham shack. There by having only to use the Lap Top PC to update the
> frequencies between the two rigs.
>
> I bought a second hand FT-3000M (Like new) off E-bay this past week.
> Basically it appeared to be working well when I was testing it last
> night for the first time. Then a minor problem popped up.
> Minor, but worth noting. I was talking with my fried across town using
> the rig
> in the house using high power, when the two muffin fans mounted on the
> rear heat
> sink started up. It was strange because the fans were inducing noise
> into the
> transmit side of things. Nothing could be heard in the receiver and the
> fans
> could not even be heard in the shack. My friend told me it sounds like I
> had
> a siren going off in the background as the fans came up to speed.
> Listening in on a local receiver, I could also hear the fans, like he
> said!
> Sirens.
>
> Like most hams, the first thing you do is pull off the cover!
> (Hey it's out of warranty!) With the rig sitting in my lap,
> turned on and running at high power. Again the fans kicked on....
> nothing could be heard on the other end or in my local receiver. All
> I did was to remove the bottom cover. Hummmm.
> Put the cover back on the FT-3000M and the noise came back.
> Now while it appears that I've fixed the problem, I'm not 100% sure why.
> But I can guess. Looking at the bottom circuit board where all the
> components
> are mounted, I the bottom cover and slightly bent the cover outward just
> a tiny bit, not even enough so that it can be seen.
> Then looking at the circuit board and majority of the guts to
> this rig, we see four small boards that sit in a vertical position.
> The boards are just covered with (SMD) surface mount components,
> transistors, capacitors, resistors and so on. My conclusion is that one
> of the boards must hold the microphone pre-amp and what ever induction
> or vibration that was felt through the case covering must have just been
> enough to modulate the rig when the fans kicked in and started
> blowing. I decided to take three strips of electrical tape and cover the
>
> inside of the transceiver cover, just one piece each on the inside cover
> above
> each circuit board. Not too much tape, just a small amount to avoid a
> mess
> later when the tape gets old. I put the cover back on the FT-3000M and
> NO MORE PROBLEM, fixed.
>
> One other small thing I noticed. The power output on my Bird Watt meter
> appeared to be a bit low. The rig has four power settings. Without
> getting
> into all the details. I basically did a reset of the transceiver as per
> the
> owners manual and now all power setting are back up to normal.
> I have no idea what exactly was reset, but the power comes up
> to spec now.
>
> I hope this helps someone down the line, when you pick up a
> second hand rig you never really know what your going to run into.
> The FT-3000M purchased new from AES last year never does not appear
> to have any signs of the fan noise problem.
> Best Regards to the group.
> Carol L. Maher
> W4CLM
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