Repair the VRF Preselector into the
Yaesu FT1000 MarkV & Field models by IC8POF
(Click on any of the images in this
repair to view them full size)
Link to IC8POF Web Site
Problem: My rig is now 3 years
old in jan.2005. One day pressing the VRF ON\OFF key the
received signals sounded not more so clear and loud. The
intensity of the signals was going up and down without any QSB
... What was happening?
At once the brain run in a sort of flowchart list for a possible
cable break from the antenna down to the rig, but all the
cabling were and are OK.
What and where the received signal could be interrupted in such
a "strange" way was not clear at that moment. So I switched the
rig OFF waited some seconds and re-ON, pressed again the VRF
knob and all seemed ok. OK go to listen again on the band for a
possible QSO. Had some contacts around and all seemed ok. Then I
played again the VRF switch to ON, all was OK. Back to OFF and
the signals disappeared with an up\down intensity. Again the
received signals were going up and down, but not due to a QSB.
At this time I was realizing that something inside the rig had
gone wrong .
Remembering of the old days when a faulty contact could be cured
by tapping on the case, specially the TV and Radio sets with lot
of tubes, I gently went to tap on the rig's chassis with the
fingers, but nothing happened . All the front switches had been
turned and pushed, but nothing happened other than each own
predefined function . Then I pressed the MOX button ( the VRF
was OFF with almost all the received signal attenuated) just for
curiosity and because I guessed that the TX knobs had nothing to
do with a faulty RX_signal_chain. At once the rx-signal came out
again in its original strength.... That was strange, but so it
was. And I recalled that in a TRX rig there are many circuits in
common or switched IN&OUT from RX to TX and vice versa. Every
time I switched the VRF_Off the rx-signals disappeared and when
I pressed the MOX the signals were back again.
The rx-signal attenuation with the VRF_Off disappeared every
time the rig was turned back from TX to RX. That is why I have
never noticed that fault before.
Solution: Having discovered the
fault was not all. It had to be ensured which component
caused the problem. Studying the electric schematic was a first
step. Tracing the received signal on the paper is quite simple.
Untill the rx-signals reach the preselector there are no active
components, only relays. Therefore I supposed that it should
be a faulty relay (Rel1005) . It is the relay that switches the
rx-signal into the VRF chain . BUT :
How to ensure myself that
was a faulty relay the cause of such incorrect reception?
EASY : open the rig , access to the RF_board, switch it ON and
tap with a pen
on the board and the relays and see (better listen) what
Easy to say but harder to do.
Because the part to check is well packed inside the
FT1000mk_V_Field rig. Follow this link for a step_by_step
How_To access into the rig explanation , for you will be
easier than for me the first time. Having the rig opened and
secured that it can be switched ON without any error
, you can try to "tap" around on the relays with a pencil.
IMPORTANT : tap very gently on the relays. I discovered almost
soon that if the tap had been strong then also some other relay
could move its anker not only the one suspected to be faulty.
Repeat more times the tapping over the suspect relay to be sure
that it is the faulty one. Now you must decide only when to
replace the relay. Follow the "Access into the Rig" procedure
and change it.
|VRF Block Diagram
Tools needed :
A screwdriver, a small soldering iron (8/15 watt) or a regulated
one, a desoldering pump, a magnifier glasses and of course a
couple of those famous TX2 relays as this one in the photo
But where could be purchased
such Nais Matsushita TX2-12V relays ? Most furnished electronic
shops list this item.
I found it at a well known supplier in EU_lands: Conrad
Electronics at www.conrad.de
Its part number is : Artikel-Nr.: 504788-14 SIGNALrelays TX 2U
2A 12V at 4,76 EUR for 1 piece. (still same price on feb2006)
and for the magnifier glasses I have chosen a head magnifier
with interchangeable lenses as this one: KOPFBANDLUPE +
SCHEINWERFER, VERSTELLBAR Artikel-Nr.: 812379-14 Preis 35,95 EUR
Third : how to remove such mini relays ?
Well, once the faulty item is found it is not so much difficult
to get it out of its place on the board.
taking the relay out
testing for the new one
showing the new soldering
The 3 photos above show the
few steps needed to do the change. Sucking the tin from the
relay pads is easy. Should be used a vacuum sucker care must be
taken to the board pads. The copper pads are not as strong as
one may imagine.
The following picture shows how looks like the VRF circuitry on
the RF board.
Reclosing the rig : be
careful to route all the wires and cables away from the possible
pinching of the screws.
Enjoy using your re-vitalized rig and use as less as
possible the VRF tuning and bypass relays.
Notes on the
Yaesu FT1000 mkV & Field preselector.
I own this fine rig since 5 years. The only
complaint I have about it is the VRF feature. First because it
is not as effective as the publicity promised and my
expectations were, second because the relays used in the VRF
unit are fragile compared to its product specs and third because
to replace a defective relay is not an easy exercise. That is a
big handicap for such an equipment. Specially when this failure
happens hundred of times around the world as the FT1000MP
reflector and my email correspondence show.
Therefore my advice is :
do not use the VRF :-> ,
or use it at minimum possible ,
turn the VRF tuning knob SLOWLY ...not
like a F1 steering gear!
be prepared to repair the radio .
I still consider the MkV series a very good rig. Even if my 15
years old FT1000 listens to every signal the MkV does . The
future will show if the new FT 2000 & 9000 models will have a
REALLY better VRF in construction and functionality of the
MP MkV series . Comments and improvements will be appreciated.
73 de Phil IC8POF