EB5AGV's FT-102 relay substitution TUTORIAL

Keep them glowing!

FT-102

One of the best known troubles of the FT-102 is the long term
life of its relays. All FT-102s are at least 15 years old. Relay technology (and
prices!) has changed a lot in those years. The standard FT-102 relays were made
by Fujitsu (except for RL01 in the Relay Unit) and were not sealed. So dust
could get into them and, finally, make them fail. You can easily find if your
FT-102 has flacky relays: when you go from transmit to receive and you get a
deaf receiver, that is!. Also, if you toggle the RF amplifier you could get
similar results. There are some relays which do other tasks in the rig, as RL01
in the IF Unit, which switches the S-meter from receiving signal level (RX mode)
to ALC (TX mode), RL01 in the Local Unit, which works on the CLAR circuit (it it
fails, frequency will jump from some Hz to full kHz). So, any sign of these
troubles is indication of a relay failure.

Cleaning the relays is just a temporary solution which does not last long, so
I recommend changing all the relays same time. I have done it myself in the
first FT-102 unit I had and it was a 3 hours work. I still need to work on my
current unit; I have the 'relay kit' ready to go and just need some time...

For replacement I used OMRON relays. All the FT-102 relays have a current
OMRON equivalent (sealed and with better electrical characteristics than
original ones) EXCEPT for one relay, which had a very curious (and exclusive)
pinout (shown in a picture below). So curious that the only way to replace it is
making an adaptor with an IC socket and some rewiring in the PCB. By the way,
Fujitsu, the original manufacturer of the FT-102 relays still manufactures some
of them but I won't buy again the non sealed relays and will get the OMRON or
Fujitsu sealed types. Price difference is really low and sealed relays will last
lots more. For your reference, a complete OMRON relay set was about $45 one year
and a half ago, here in Valencia. Slight differences in nomenclature of the
relays (as G2E-184PM/12 and G2E-184PHM/12) are not a trouble; in fact, the
references I have put in the table are the ones I was able to locate here in the
OMRON Valencia branch.

The relays which are more prone to fail are the smaller low signal relays so
I recommend changing all of them and then checking for correct operation before
changing RL01 in the Relay Unit.

FT-102 Relay Substitution Table

Board or Reference

Standard relay

OMRON replacement

Fujitsu replacement

RF Unit (PB-2342)

RL01, RL03

FBR211A DO12-M

G2E-134PHM/12 or G2E-184PM/12

FBR211-NAD-012-P

RL02

FBR221A DO12

G6A-234P ST US/12 (NEEDS REWIRING)***

RL04, RL05

FBR211A DO24-M

G2E-134PHM/24 or G2E-184PHM/24

FBR211-NAD-024-M

IF Unit (PB-2343)

RL01

FBR211A DO12-M

G2E-134PHM/12 or G2E-184PM/12

FBR211-NAD-012-P

Local Unit (PB-2345)

RL01

FBR211A DO12-M

G2E-134PHM/12 or G2E-184PM/12

FBR211-NAD-012-P

Final Board (PB-2355)

RL01

FBR211A DO12-M

G2E-134PHM/12 or G2E-184PM/12

FBR211-NAD-012-P

Relay Unit (PB-2354)

RL01

OMRON G2U-112P/10V

G4S-112PB/12 or G6B-2114P-US/12

TUTORIAL
These are the compiled notes and pictures I took in my last
FT-102 repair. I got this nice unit about a year ago and it had the original
relays. As expected, unit had the well known troubles with them, so I got a new
batch of OMRON relays and saved them for future use... Finally, I was able to
accomplish the task. All the work, done very carefully, was about four hours. It
can be done in less time but, as this repair will last at least 20 years, it
pays to do it without hurry. Anyway, this is a hobby!

Well, first step is to undress the rig (i.e. pull out covers). First the top
cover and then the bottom one. Setup a good workbench space. A desoldering
station (mine is shown in the picture) is a really nice tool for this work.

Put the rig upside down, as shown below.

RF UNIT RELAYS
We will start with the most conflictive relays, those in
the RF unit. In order to access to the solder side of this unit, we will remove
the AF unit (4 screws) and the RF unit shield (2 screws). Then put the rig over
its side, with the AF unit hanging on its wires.

We need to locate the relays in the RF unit. Here you have them (looked from
the component side of the RF unit):

Replace RL1001, 1003 and 1004, which are easy to access. Note that the last
one is 24VDC.

As you can see, RL1005 is almost hidden by a rotary switch (attached to the
BAND knob). In order to change it, we will need to unsolder this rotary switch
along a bridge which is just over it:

Then unsolder all the pins of the relay and carefully pull the rotary switch
to free it. This could take some time... patience pays!.

In order to replace RL1002, as it is a non-standard relay, it is better to
build an adapter, based on an standard 16 pil DIL socket and then just rewire
some PCB traces. Here you have the pictures to do this:

This picture shows the wiring of the socket adapter, based on a 16 pin DIL
socket and also the internal configuration of the original and replacement
relays.

Here you have the necessary changes to do in the PCB. In figure 1 you have
the original PCB traces. Cut the traces at points 'A' and 'B', as shown in the
figure 2. Then put wire bridges as shown in figure 3 (discontinued lines),
crossing 'A' and 'B' and then another one in 'C'. Enlarge hole 'D' to prevent
contact with this pin. Put the socket adapter and plug the OMRON G6A-234P relay
on it. Then, the connection which was soldered to point 'C' goes now to point
'D'. Here you have a picture of the modified zone:

You can now resolder the rotary switch and put the RF cover and AF units
back. Once done, you can check the rig. Most of the relay problems should be
gone by now!

LOCAL UNIT RELAY
The LOCAL unit is also accessible from the bottom side.
This unit has only one relay which serves to switch the CLARifier. So when it
fails, you will get nice frequency jumpings in CLAR mode... Not too fine!.

Get out the 7 screws and unplug all the connectors. BEWARE: my unit have
three soldered wires which are attached to the LOCAL unit. I managed to change
the relay without unsoldering them, but you should be careful in order to keep
them unbroken.

FINAL UNIT RELAY
This unit is also accessible from the bottom side and
has only one relay which seems to switch some PA tubes control voltages.

In order to save lots of time opening PA cage, removing tubes and so on, you
can try to get out the relay without dismantling the board. I did that way and
it was just a 20 minutes job.

IF UNIT RELAY
Put the rig in its standard position, so you can access to
the upper side.

The IF unit has only one relay. This unit is the one which holds all the
standard and optional filters. The relay is located side by side to the 455kc
filters (near the back of the rig), hidden below a bunch of wires.

If it fails, you will get jumpings in the S-meter indication on receive and
ALC on transmit, but it will affect only to the meter, not to the real signals.
Anyway, it is worth changing it. You will need to unplug all the connectors in
the IF unit (a LOT of them, really!). Be VERY careful with the coaxial
connectors. Pull them from the metal part, NOT from the cable, as it is
delicate. Write down the colors of the coaxial wires and its location (a fast
sketch is just fine). Once you have done that, get out the 6 screws and
carefully remove the IF unit. Change the relay and put it back in reverse
sequence. Now your S-meter will be fine again!.

Well, I hope these notes could lead to a full working FT-102!. Please, let me know if you have any doubt or comment
about the information shown in this page.

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