EB5AGV's FT-102 Relay Substitution TUTORIAL
A new lease of life for your FT-102
Yaesu FT-102
One of the best known troubles of the FT-102 is the long term life of its relays. All FT-102s are close to be 30 years old. Relay technology (and prices!) have changed a lot in these 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 four hours work. I have also done my second unit with excellent results.
For replacement I used OMRON relays. All the FT-102 relays have an 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 later). 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 (back in 2000; now some of the relays are obsolete types), 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.
Relay Substitution Table
| Board or Reference | Original 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 | G8SN-1C7-CUK/12 | |
| MOST OF THESE RELAYS ARE NOW OBSOLETE BUT SOME CAN STILL BE BOUGHT AT RS-COMPONENTS |
TUTORIAL
These are the compiled notes and pictures I took in my last FT-102 repair. I got this nice unit still fitted with 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 should last several 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.
IMPORTANT: USE THE SHORTEST POSSIBLE LENGHT OF WIRING AND; IF AVAILABLE; USE SMALL GAUGE COAX.
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.
NOTE: I DON'T STOCK REPLACEMENT RELAYS, SORRY!
FT-102 Yahoogroup
If you are interested in this transceiver, please, join us at the
Yaesu FT-102 Yahoogroup - Since 2001!