Hi all,
Update:
As suggested I checked out the switching diode on the LPF board to find that
it measured the same in both directions.
Not shorted or open but with a resistance of around 5500 ohms each direction
the diode was obviously faulty.
I found the specs for the GM-3B diode on the web and it is a 1000v 2.7 amp
rectifier diode.
I was a little reluctant to use a 1N4007 as Dave WA0ZZG did, as it has only
a 1 amp rating (even though they are known to have similar qualities to PIN
diodes) and elected to fit a 1N5408.
So far all tests show that the extra signals in the receiver have
disappeared and there seems to be no trigger to start them off again.
TX output is normal and the radio appears working as it should be.
Thanks to all for the comments on and off-line and especially Dave WA0ZZG
for your assistance with this problem.
73,
Chris ZL2DX.
------------------------
Hi Dave,
Thanks for the comments.
Another station replied direct with a similar comment.
Quote------------------
I had the same problem with my MkV exactly 5 years ago after my tower was
struck by lightning. I knew the thunderstorm was coming and took the proper
precautions (I thought!). I switched the rig to "dummy load" on my Bird
antenna switch, and disconnected all the rotor control cables from their
controls. This, however, was not enough. As I found out the hard way, the
FT1000 is unusually susceptible to lightning, even near misses.
What has happened, is that some diodes in the T/R circuitry have been
shorted by a nearby lightning strike. Even though mine was turned off at the
time and switched off and of the antenna(s), enough pulse came through on
the ground braid to do the damage. Never would have happened on an older
tube rig. I don't remember which diodes were damaged. I had mine repaired by
a guy in Nashville, TN who is very good with all iterations of the FT-1000,
but I guess that is not an option for you.
Nowadays, when I know a thunderstorm is predicted, I completely unhook
EVERYTHING from the radio and actually move it to a table across the room.
It's a real PITA, but only takes about one minute, and assures that it will
not be damaged.
I also found that switching the tuner in/out changed but did not eliminate
the "birdies".
End of quote---------------------
When this radio came to me it had a front end problem and appeared to have a
number of blown switching diodes in the front end of the receiver on the RF
unit.
I guessed that it had probably been in the proximity of a near miss from
lightning or similar discharge.
As I didn't then have a source of the 1SS83 didoes I used the 1N4007s but
the failures kept on and seemed to move past the previously replaced diode
to the next diode in the chain.
I probably did 4-5 replacements like this until it was obvious that the RX
gain was dropping and the problem was still evident.
Eventually I managed to get a number of 1SS83 diodes from Burghardt's before
they closed the doors and replaced all the diodes previous swapped for
1N4007s and that particular problem doesn't seem to have re-appeared unless
this is a different symptom of the same original issue.
There only seems to be a single GM-3B diode in the signal line on the LPF
board so I will put the radio on the bench again and check it out and report
back.
Thanks and 73,
Chris ZL2DX
-----Original Message-----
From: yaesu-bounces@contesting.com [mailto:yaesu-bounces@contesting.com] On
Behalf Of Dave Maley
Sent: Sunday, 2 January 2011 1:57 p.m.
To: yaesu@contesting.com
Subject: [Yaesu] . FT-1000 mystery signals? (Chris Hannagan
This is really going to sound strange, but I had a similar problem with my
'1000D. Drove me nuts. Finally found it. Mine was on the LP filter board.
Here's what I found. The transfer circuit uses a small relay to switch the
receiver on and off the antenna, and a pin diode to switch the transmitter
in and out. Check the pin diode with an ohm meter after lifting one side.
Mine was a dead short. The radio still works. Just makes a mess of the
front end. I couldn't find the exact replacement specified by Yaesu, so I
used a 1N4007 diode. It's been in there for several years. Why it comes
out like you described, I have no idea. You should see the mess it made out
of the AM broadcast band. Let us know what you find.
de Dave
WA0ZZG
----- Original Message -----
From: <yaesu-request@contesting.com>
To: <yaesu@contesting.com>
Sent: Saturday, January 01, 2011 2:00 PM
Subject: Yaesu Digest, Vol 97, Issue 1
> Message: 2
> Date: Sat, 1 Jan 2011 18:33:37 +1300
> From: "Chris Hannagan" <zl2dx@xtra.co.nz>
> Subject: [Yaesu] FT-1000 mystery signals?
> To: <yaesu@contesting.com>
> Message-ID: <016601cba975$711c50e0$5354f2a0$@xtra.co.nz>
> Content-Type: text/plain; charset="us-ascii"
>
> Hi All,
>
> My FT-1000 has an unusual problem and I would appreciate some help to
> track
> down the issue.
>
> On the bands there are extra signals being generated in the receiver.
>
> I can hear a "copy" of the original signal every 17.4-17.5 KHz away from
> the
> real signal but decreasing in signal strength each "17 KHz step" away.
>
> On my local 10 metre beacon for example, I can hear these "copies" to well
> above 29 MHz.
>
> As you can imagine it makes 20 metres sound really busy in a contest but
> often the signal I'm hearing is not the fundamental one..
>
> This "feature" switches off by momentarily putting the tuner in line. It's
> not necessary to actually have the tuner operate.
>
> The extra signals re-appear when the rig is momentarily put into TX mode.
>
> Possibly related to this is that when chatting on 75 metres, on returning
> to
> RX there are often strong whistles (carriers or images?) that sweep across
> the received frequency for about 2 seconds or so.
>
>
>
> I would appreciate any assistance with this and would like to hear from
> anyone else who might be seeing the same events.
>
>
>
> Thanks and 73
>
> Chris ZL2DX
>
>
>
> ------------------------------
>
> Message: 3
> Date: Sat, 01 Jan 2011 12:51:08 +0000
> From: "K1TTT" <K1TTT@ARRL.NET>
> Subject: Re: [Yaesu] FT-1000 mystery signals?
> To: <yaesu@contesting.com>
> Message-ID: <14E27F5656B64F57BC2CDE7184F7DABF@k1tttibm>
> Content-Type: text/plain; charset=US-ASCII
>
> Yes, that is odd. I have never heard of one that bad, especially at such
> a
> low repetition rate so this is just a guess. Normally you get images like
> that when there is a very strong signal mixing with the desired one enough
> to cause distortion in the receive chain. Since it goes away when you put
> the tuner in line that would tend to indicate that it is in the first rf
> mixer, the tuner would act as an attenuator if not tuned, or as a
> preselector if it is... does turning on the radio attenuator also get rid
> of
> the products? Do you have a signal generator so you could eliminate
> external sources, just to be sure its not something gone bad in the radio?
>
> When you say it returns after tx, does that mean that when you have the
> tuner in line, then tx, then go back to rx they are there? Does the tuner
> stay in line or drop off or automatically tune itself??
>
> If it is an external mixing source the key of course is to find it. The
> 17khz step is probably related to the device that is generating the
> interfering signal. That frequency could be a monitor, tv, switching
> power
> supply, LED lamp, just about anything new that was installed about the
> time
> the problem started, and probably pretty close to the antenna. Double
> check
> shield connections on coax IN the shack, and all ground connections also
> to
> make sure you aren't picking up noise from a monitor or something else in
> the shack. Otherwise you are on a hunt for a loud signal around that
> 17khz
> range, if you can pick it up on a hand held shortwave receiver that would
> help.
>
> The sweeping carriers on 75m could be related. Its possible your tx on
> that
> band is disrupting the device a bit and shifting its frequency. After you
> stop transmitting it goes back to its normal frequency. However, I have
> seen one like this caused by an oscillating voltage regulator in an
> amplifier. As the temperature in the amplifier changed the regulator
> oscillation frequency changed. Do you hear carriers every 17khz across
> 75m?
> if so they could be used to help track the source.
>
>
>
> David Robbins K1TTT
> e-mail: mailto:k1ttt@arrl.net
> web: http://www.k1ttt.net
> AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
>
>
>> -----Original Message-----
>> From: Chris Hannagan [mailto:zl2dx@xtra.co.nz]
>> Sent: Saturday, January 01, 2011 05:34
>> To: yaesu@contesting.com
>> Subject: [Yaesu] FT-1000 mystery signals?
>>
>> Hi All,
>>
>> My FT-1000 has an unusual problem and I would appreciate some help to
>> track
>> down the issue.
>>
>> On the bands there are extra signals being generated in the receiver.
>>
>> I can hear a "copy" of the original signal every 17.4-17.5 KHz away from
>> the
>> real signal but decreasing in signal strength each "17 KHz step" away.
>>
>> On my local 10 metre beacon for example, I can hear these "copies" to
>> well
>> above 29 MHz.
>>
>> As you can imagine it makes 20 metres sound really busy in a contest but
>> often the signal I'm hearing is not the fundamental one..
>>
>> This "feature" switches off by momentarily putting the tuner in line.
>> It's
>> not necessary to actually have the tuner operate.
>>
>> The extra signals re-appear when the rig is momentarily put into TX mode.
>>
>> Possibly related to this is that when chatting on 75 metres, on returning
>> to
>> RX there are often strong whistles (carriers or images?) that sweep
>> across
>> the received frequency for about 2 seconds or so.
>>
>>
>>
>> I would appreciate any assistance with this and would like to hear from
>> anyone else who might be seeing the same events.
>>
>>
>>
>> Thanks and 73
>>
>> Chris ZL2DX
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