OBSERVATIONS FROM SCOTLAND

OBSERVATIONS GM1SXX 06 November 2010

The Yaesu FT-102 and that RL-02 relay

I bought my FT-102 transceiver about two and a half years ago. Since then, it has become my favourite radio of all time. You can read about the relay and other problems I had with it in earlier postings, but suffice to say that after changing out most of the relays for new sealed types, it has given me over two years of absolutely superb service. I operate mainly on data-modes on 20 and 17 metres and the FT-102 makes a superb data-mode radio. I've noticed however that of late, that sometimes when going back to receive, the signal strength drops a bit so I thought it was time to attack the infamous RL-02 on the RF board. This relay stirs up a lot of controversy among FT-102 aficionados because the original relay was discontinued a LONG time ago and there are no direct replacements.

The relay was originally made by Fujitsu of Japan , and was relay type FBR221A DO12

Two trains of thought seem to prevail.

1) Send the original relay to Mal N4CL for a refurbishment job

2) Do the EB5AGV mod, which consists of changing the relay for a modern one and 'rewiring' the PCB foils to match. More at.... http://w8kvk.com/nc4l/page6/page6.php

I chose neither of these routes. Instead I removed the original Fujitsu relay and fitted a socket fashioned from turned pin strips, into which I plugged a mil-spec TO5 canned RF relay.

The preferred relay for this is the Teledyne 712-l2. It has a 12 Volt coil. It is expensive.

Being me, I couldn't find that particular model of RF relay but I did find three TO5 RF canned relays for £10 on EBay, which with a little rearrangement of the wires could plug into the original relay's 'footprint', without too many strays. The relays I got were model M39016/9-105L. They appear to be a 9V version of the Teledyne 712-12 relay.

It's said a picture is worth 1K words, so here are some pictures.

One of the canned relays.. I believe made by Teledyne. The coil voltage is 9V, not 12, so I had to use a series resistor (more later).

The FT-102 on the bench, before being stripped down. Note that the paint on the FT-102 chips easily, so when I was working on the radio, I padded the bench with some cardboard to help protect the paint.

Here you can see the 221DO12 relay in the RF unit. You DON'T need to remove the RF unit for access. Instead, turn the radio over and take the screws out of the AUDIO board instead.

I did end up removing the spindle-coupler you can see in the foreground (photo above) to gain better access. It operates the plate tuning... so make a careful note of the orientation of the PA tuning capacitor plates against the position of the knob. If you don't... you will soon wish you had!

Here you can see the radio upside-down and the audio board folded back on itself after I removed the fixing screws . I also removed the small connector with the red and brown wires. Be careful.. they are very thin wires.

I took this photo so you can see that I 'wired' the PCB to a frame lug to stop it from moving while working on the set. This protects the wiring from being stressed. You can see the wire threaded through the fixing-hole on the edge of the PCB and the threaded hole on the case.

Here you can see the connector (top right) with the red and brown wires that I disconnected. To get at the RF board, you must also remove a metal screen that covers the opening you see here. Near the top of the opening you can (just) see two black pointers drawn where the fixing screws go. One of the fixings also holds down a tag-board and has a washer attached. DON'T mix up the screws. The FT-102 uses a lot of different screws that look quite similar... but are not. In the centre of the photo sitting on the metal screen, is the faulty relay I had just removed. The relay connections on the PCB are above the two trimmers with the green wires. Here you can see the holes where the relay pins went. You can also see the gunky flux residues left behind by the de-solder braid I used. PLEASE use a temperature-controlled iron when you work on the FT-102. Many soldering irons run far too hot for this sort of phenolic PCB and will cause it to crack or de-laminate. I used 'Cyeco WICK' de-soldering braid to mop up all the solder from the pins.

That's 'de-sole-der-ing'... not 'de-soddering'... and 'sole-der'... not sodder. Get it right guys! The English language doesn't have many silent L's. Examples...L is often not pronounced before L, D, F, M, K. Examples....calm, half, salmon, talk, balk, would, should...... errr solder? I'm afraid not.

The de-soldering process takes a little time and patience but it works very well. I turned over the radio and lifted the relay straight out...I had no stuck pins!

Here you can see an extreme close-up of how messy the PCB looked after the de-soldering job. Pretty messy! I cleaned up the mess using cotton buds and neat isopropanol. I managed to get the board back to an 'as-new' condition this way. Always take a lot of digital photos when you repair radios... just in case anything falls off, or you forget which wires go where!

Above is a somewhat fuzzy extreme close-up of my TO5 relay mounted on the turned pin socket. Note that some pins of the socket need to be snipped off so it fits through the PCB holes. Use small flush cutters.

Because the new relay pin-out differs from the original, you have to rearrange the wires to connect the appropriate wires to the appropriate pins.

The original relay (looking from above) has the pins arranged...

COMM COIL NC NO

The arrangement of the Teledyne 712-12 and the M39016/0-015L relay is as follows

COIL COMM NO NC

This means that the wires must be twisted with ....

COIL and COMM pairs reversed, and

NC and NO contact pairs reversed.

You can see how this is done in the photo below. Once arranged like this, the relay can be re-fitted to the radio in the correct orientation and the pins soldered into place on the PCB. Note also the 'missing' pins on the turned-pin strip. I snipped these out using miniature flush cutters. This allows the revamped relay to simply slot in to the existing PCB and be soldered in place.

Here's another shot of my relay, 'resting' on top of the PA cover. The tab on the relay is facing to the right. The wires are further apart than they appear to be in the photo. The writing on the PA cover is 'non-standard', just a reminder 'from me to me' that there are lethal voltages inside that box!

I soldered the new turned pin socket into the original relay pin holes No mods required except for one track cut. If you use a 712-12 relay instead, you wont need this resistor. Remember, my relay has a 9V coil, so I added a 68R resistor in series with the coil to drop the required 3 volts DC. I made the single track cut (left side of the resistor) using a diamond tipped dental 'drill' that I 'borrowed' from my dentist. I mounted it in a Dremel machine so I could make a neat track cut.

You can see the resistor and track cut better in this shot. Note the nice clean PCB around the relay area.

All back together and in pride of place in my messy shack. The radio to the left of the FT-102 is a TS-820S. An FT790 and FT290 sit on top.

Back on the bands. My first contact using the new relay was with F4EDZ. very easy contact. Welcome back old pal!

73 Al.

GM1SXX

Post Scriptum 07/11/2010

Does this modification work? Well, indeed it does. I've worked a good number of stations since re-assembling the radio and on receive I'm seeing no more signal drop-outs. It performs better than before. I saved the old relay, just in case I ever want to have it refurbished, but somehow I doubt if I'd bother doing that. I'm very happy with this mod.