ft102mod

COLLECTED FT102 FAULTS/MODS/MISTAKES (Thanks to all) Author: G3RZP -

The relay problem you can fix easily by a few careful cuts of the tracks on the PC board, and adding a few 22k resistors and blocking caps. This mod bleeds some DC through the relay conatcts and breaks down the oxide film. Mine is still on the original (1983) relays. The real nasty in the 102 is if you are a CW DXer, especially on the low bands. The key clicks on certain production batches are beyond being fit for human consumption, but that is easily cured, and not by the recommended Yaesu mod. It may well be found that the documentation and the actual rig don't match, too, when you get down to PC Board details. The crystal filter arrangement leaves a lot to be desired - CW wide is SSB bandwidth, CW narrow cascades all the filters. Easy to add a couple of diodes to arrange CW Wide to be a wide (800Hz) CW filter and CW Narrow a narrower filter. The real killer is a receiver spurious on 80 and 40, where a strong signal on 3500kHz or 7000kHz breaks through, getting weaker as the rig is tuned up the band. This is caused by the 6MHz signal used to mix the VFO down to 500kHz to 1MHz bleeding across the dual gate MOSFET mixer, and substituting an IC mixer cures that. Although it took me 17 hours of solid work one weekend to find and cure, and me! ant borrowing more test gear from work than my house was worth at the time! Another CW problem was a lazy crystal for the CW tx carrier generation. Seen this on a couple of 102's, and dropping the FET source bias resistor gives that extra bit of gain so you don't start calling 'RQ CQ CQ' because of the crystal taking time to start. Some FT102's have a diode in series with the PA screen grid; this can lead, especially with older well worn tubes, to plate current runaway if/when you get negative screen current. By removing this diode and adding zener screen regulation and zener stabilisation of the bias and selecting 3 tubes with identical plate currents, that problem can be disposed off. I've done a number of contests over the years, a lot of ragchewing and DXing, and 2 of the PA tubes are the 1983 originals: the other one is a better match to the two: it dates from 1971, and I used it at work in a commercial transmitter development. Some 102's can be a bit unstable on 80 when operated into anything other than 50 ohm wideband load. A damping resistor and series cap in the PA grid fix this OK, and by choosing the correct point, it's only switched in on 80. Why the FT102 has such a quiet local oscillator is a bit beyond me. There's nothing special about the VCO design, but it's really good. I measured input third order intercept at +16.5dBm. That is OK: I've not yet had the situation where IMD has been a limit (I have biggish antennas - 5 ele monobander on 20m and so on) Getting extra crystal filters is not so easy. I got a narrow (1.8kHz) filter from International Radio at Dayton this year. George, W2VJN, warned me that he didn't have a mechanical drop in filter, but did have an electrical fit filter. That needed a couple of its ground pins clipping off, and two holes drilling in the PC Board to make it fit - no big deal. But fully kitting up a radio won't be cheap, although from a performance viewpoint, well worthwhile. Some of the ICs aren't readily (or at least cheaply) available, but there's enough room in the 102 that it's not difficult to rebuild a bit of circuitry around what can be got. The likely

biggest problem will be if the display goes, as those are made of unobtainium! Even then, it's not that hard to make something up, together with a new counter board. Quite a few modern rigs with custom ASICs in will give maintenance problems in a few years, when the manufacturer no longer has any stock.......expensive junk piles will be the result!

G3RZP

RECT A BOARD: Here’s an interesting one, the Technical manual says R02 39 ohms, and R01 390 ohms, this is wrong, but the board is correct, the resistor numbers are reversed …..de G4ICD

Fault Operating tx and notice bias current too high and drifting up, and plate current too high on tune up. Even with bias turned to minimum Although it would tune up to about the right power, could only get about 20 watts on a whistle on ssb. But NO!, no change with new valves. So I got technical and measured the bias voltage which was about 20 volts too little. Turned out to be the reservoir capacitor in the bias supply circuit C8011 a 33uf at 250volts on the Rect A unit board, the one diagonally closest to the bias set point pot.

Now the pot allowed me to cut the valves off completely once again.

UNLOCKED UNDER 7.300MHz. Hey guys I recently acquired a Ft 102 that works great except on 40meters the display gets erratic and the radio comes unlocked below 7.300. All the other Bands work normally and the vfo has full range. Has anybody run into this? I recently replaced the FET near the out put on the IF board because the receiver was numb. Now the receiver is .270uv with the RF amp. Ok I found the problem while doing a complete alignment. L4006 had a bad solder joint and was causing the radio to come unlocked. Re-soldered the can an all is well. FYI the component I replaced in the IF for the numb RX was Q10 this also supplies some signal to Q14 for the S meter. All is well now

MORE IDEAS FROM PETER G3RZP RE NO 7MHz Start by looking with the counter (DC isolated) at Q24 pin 12. You should see something between 5 and 5.5MHz that varies with the VFO. Now look on TP03: you should see 6 MHz. IF OK so far, go to J13, pin 1: you should have something that varies from 500kHz to 1MHz, following the VFO. The VFO gets mixed with 6 MHz to drive the counter. Switch the marker on (back panel) As you tune through each band in turn, can you hear the marker harmonics? If not, connect the counter (DC isoltaed, using a high impedance probe) to Q12, pin 5. You should get a signal, probably pretty unstable, at around 10 MHz when on 160, 12MHz on 80, 15 and abit on 40, 18.5 on 30, 22.5 on 20,27 on 17, 29.5 on 15, 33 on 12 and 37MHz. +/- on

10. This tells you if the various band VCOs are performing. Now look on TP 05. You should have a signal here of about 60mV, frequency: 160 to 30 m : 13715 to 14.215 MHz 20, 17m : 23.715 to 24.215 MHz 15, 10m: 33.715 to 34.215 MHz At Pin 4 of Q17, you should see (but you won't if the PLL is unlocked). You will probably see some sot of signal around these frequencies. 160 - 4MHz, 80 - 2MHz, 40 - 1.5MHz, 30 - 4.5MHz, 20 - 1.5MHz, 17 - 2.5 MHz, 15 - 4.5 MHz, 12 -1.0 MHz, 10 - 2.5, MHz, 3.0 MHz, 3.5 MHz, 4.0 MHz as you got through the band segments. If you have signals here, a 'scope is the best bet to look at the output of the 74LS192 on pin 13. If there is input on pin4, and no output, check pin 11 is at the same level as pin13. Is the 4.3 volts on Pin 13 steady, or are there pulses? Check too, for 5 volts on Pin 16 and 0volts on pin 8, in case of bad joints. If there's output on pin 13 of Q17, look at pins 1 and 3 of Q18. With the loop unlocked, you should see pulses on pin 11. If not, I would change Q18. If you do, get a spare while they are available. Hope this helps Peter G3RZP

YAESU FT-102 FAULTS/MODS LOW RX SENSITIVITY : Check aerial i/p fuse which is a small wire ended bulb located on the small pcb in the top PA compartment. It is not possible to use any old bulb here as most could give several dBs attenuation. The antenna fuse bulb is around 9 to 10 ohms. (Wheat bulb)

INTERMITTENT LOW RX SENSITIVITY : Suspect the relays on the RF pcb around the RF amp. Note that some of the relays are 24v types and not the more usual 12v. Don't miss the relay at the front of the board under the shaft of the bandchange switch which is not that bad to change

RF AMP NOT WORKING : Check the relays which switch the RF amp and then check the two fets in the RF amplifier (2SK125). PRESELECTOR NOT TUNING CORRECTLY : There is a shaft coupler on the bandswitch shaft - if the screws in this are loose it is possible for the front and rear sections of this switch to be out of physical alignment.

NO RF OUTPUT (PA DRAWING CURRENT AS NORMAL) : The main aerial changeover relay (on pcb in the top PA compartment) has been known to burn out. VARIOUS PA FAULT CONDITIONS : Check for physical short circuits around the band switch in the PA compartment. I have once had burnt out tags on the band change switch this was impossible to see before I removed the switch. FLUCTUATING POWER OUTPUT : check the PA valves and check the PA anode choke. Sometimes this is caused by slight band switch problems, move the switch a little and the power comes up, so re-align the shaft/coupler cures the problem. INTERMITTENT MAINS FUSE BLOWING : Suspect that one of the PA valves is flashing over. NO TX : Check the series pass transistor in the 12v. regulator circuit. I have twice seen cases where it has overheated, melting the solder on its leads, causing a physical short circuit. NO TX - NO DRIVE : R01 on RECT A UNIT. Check driver valve after replacing this. POOR NEUTRALISATION : This can sometimes be a problem if 2 or 3 different types of valves are used in the PA. PA WON'T NEUTRALISE : I had one case where the user had connected the PA screen grid supply to a higher voltage on the rectifier unit, causing this problem. FREQUENCY SHIFTS WHEN CLARIFIER ON : Dirty contact on RL4001, the clarifier relay. FM TX WAY OFF FREQUENCY : Failure of Q13 (TC5081P) on AM/FM unit. See Yaesu mod sheet to prevent further failure. LUMPY VFO DRIVE : The couple of occasions that this has been a problem I have usually improved it by cleaning and re-lubricating the mechanism. If it’s really bad the drive will probably need to be replaced. KEY CLICKS : Some of the earlier models suffered from key clicks on CW. To cure this connect a 0.68 microfarad cap between key 1 on the REC A board and earth. DRIFT ON CW : Some of the early units suffered from a drift of 50-100Hz during the first couple of minutes of CW transmission. Yaesu suggest removing C153 (3.3 microfarad) on the local unit to cure this problem. It is located between X4002 and T4014.

NO 29-30 MHZ : See CB de-modification below. CB DE-MODIFICATION : See Yaesu mod sheet. The CB modification allowed the 2930Mhz range to cover 27-28Mhz and the counter did not display CB frequencies. Careful alignment of the VCOs is essential.

Installing those new relays in your FT-102 Several comments on this: You can use other methods here like Peter Chadwick did, or you can replace them, replacing them is a 90 min job and a little care, RL02 never seems to give any problems, so don’t worry about that one. Changing the units to sealed types cures the problems full stop. For those who have bought the FT-102 relay kits. Here are some hints to do the job. Please do not consider these to be step by step instructions, however these notes may help you do the job. Basically replacing the FT-102 relays is not a difficult job to do except for one relay that sits under the band switch, RL05 on the RF Unit. My advice on doing the job is TAKE YOUR TIME, DON'T be in a rush. Do the RL01 in the PA compartment one evening. Loosen up the screws on the rear panel that hold the rear panel to the chassis. This will allow you to pull the panel out about 1/4 to 1/2 inch. This gives you some room. Needles to say remove all the covers for first, then the PA tubes and set them all aside. There is one yellow wire at the bottom of the Relay board if you want you can unsolder the yellow wire and this will allow you to pull the board up some so you can work on it, don't pull on the wires any more then you have to.

Replace RL01 T/R relay and then reverse the process. Take your time and only do that one relay part of the job then set it aside until you

get the time to come back, don't try and do it all at once. Reassemble everything and test the rig after you change RL01 on the Relay unit (antenna T/R relay) test the rig and if all is a go, then take a break or proceed to the RF Unit.

You can remove the RF board if you wish, BUT, do not remove the shaft that goes through the wafer bandswitch: The only wafer that needs lifting up is the front one to get the relay in, unsolder the front wafer using solder wick, lift it up 5mm, pull out the old relay and insert the new one (RL05).

New RL02 Installed (See optional RL02 installation suggestion in that it is very rarely a problem and I have not replaced it)

RF Unit.... You get to the bottom of this board by carefully folding the AF board back. I recommend you take a small plastic Ty-wrap and secure the board in a laid back position when installing your new relays on the RF unit, this way the board will not be flopping around while your working in the transceiver. Use one of the screw mounting holes on the audio board, slip the Ty-wrap through one of the existing holes and secure it to the bundled package of wiring in the set, this will keep the audio board out of your work space while doing your relay replacements. I work with the rig flat on the bench, when I put in a relay I chose to hold it in place with my finger, put a small piece of solder near the relay leg and tack solder one leg in first. Push up on the relay and then solder it again, then do the rest of the leads. DO NOT bend the relay legs to keep it in place. This will make it very difficult if you ever have to replace them down the line and will ruin the board if you have to take one out again sometime in the future. More so recently: Instead of using a finger to hold the relay in place during the soldering process, I tried using a piece of cellophane tape to hold the relays in place from the top of the RF unit. This worked out nicely, then I flip the rig back over one time and solder all the connections. Removing all the relays at one time letting them fall to the bench really sped up the process. I let all the relays drop to the bench, flipped the rig over. Pushed in all the new relays into the clean holes, using cellophane tape to hold all of them in place I only had to turn the rig over one more time and I soldered all the relays at once. For more info on replacing FT-102 relays visit Jose's web page for more ideas as to how do the relay replacements, Jose has some good pictures on his site as to how he did his installation.

DO NOT UNSOLDER ALL THE WAFERS IT IS NOT NEEDED New RL05 Installed directly to the circuit board . As for RL05 under the band switch. I've heard of different ways of getting this relay in and out. All agree that you have to unsolder each leg on the front two band wafers on the band switch. I personally don't mind doing a little extra work and taking my time doing so in order to do a job right. I disconnect the loading shaft and pulled it out, also disconnected the plate shaft and pulled it loose from the front. Then I removed the three screws on the front panel right side, this will allow you to pull the front of the radio forward about 1/4 to 1/2 of an inch. For the few extra minutes in doing this, it gives you a lot more room to work with from the front of the rig. LET ME RECOMMEND ONE THING IF YOU PULL THE FRONT FORWARD...TAKE SOME KIND OF A MARKER put the band switch straight up on 18 MHz and mark the band switch before you pull the panel forward. In case you have a brain fart and some how the band switch moves, you will know where it goes back together. If you do it my way and pull the front panel forward a 1/4 to 1/2 inch BE SURE YOU DO NOT LOOSE THE BLACK PLASTIC COUPLING FROM THE FRONT PART OF THE BAND SWITCH GOING TO THE MAIN SWITCH ON THE RF UNIT. Put all screws and parts in a container and don't lose them when you work. There is a 12 VDC / 24 VDC modification that puts both RL-04 and RL05 in series. You might check and see if this modification has been done to your rig. We will discuss this further after you have completed your relay installation. Remember what I said in the second sentence at the top. TAKE YOUR TIME. Most hams have more then one rig in the shack today, so don't get in a big rush to do this job.

New RL01 & RL02 Installed on to the RF Unit. I was in no rush and even with pulling the front panel loose the whole process of replacing every relay on the RF Unit took me a little over an hour, maybe an hour and a half to do the entire RF Unit relay replacement job. You can do it how you please, but I feel by pulling the loading shaft allowed me to get my fingers into the area of RL01 / RL02 on the RF unit much more easily.

New RL03 and RL04 Installed RL03 and RL04 are fairly straight forward and easily enough to replace. Make sure when removing the old relays your soldering iron is hot enough to melt the solder but not so dammed hot you destroy the circuit board traces when removing the relays. Use SOLDER WICK to suck up the excess solder. DO NOT USE A SOLDER SUCKER. When the relay is out use the solder wick again to make sure the hole is completely clean before attempting to put in the new relay in place. OPTIONAL RL02 Installation procedure (RF Unit) An interesting idea that I have seen in several FT-102s I've serviced had this neat little modification done to the RF unit by Malcolm (NC4L) is to modify a 14 pin I.C. socket and mount RLO2 on the socket. The following pictures were sent to us from WA3URR David Hartwick.

Typical 14 Pin I.C. Socket Remove unused pins from socket leaving only those required to make contact to RLO2

Take your new socket in hand, with a good pair of cutters trim the edge of the socket so that the relay will fit firmly against the socket when installed Install your new socket in place where this relay resides.

Plug in RL02 and away you go! Nice mod Mal! I did this same modification on the last couple of rigs I worked on and it was every bit as quick and easy as installing the relay to the board itself, I highly recommend you pick up a couple of 14 pin IC. sockets and do this modification if you're planning on replacing your relays at anytime in the near future.

By the time you get this far, you have completed the hard part and will have installed six out of eight relays included in the Fox Tango relay package.

FT-102 IF Unit

FT-102 Control Unit You will install one more small Omron relay on the FT-102 I.F. Unit and one on the Control unit. Since there is only one relay on each of these boards, this should be pretty much self explanatory. After replacing these relays you are finished with the relay modification for you rig, with the one exception noted below.

Finally One last thing regarding the 12v / 24v relay modification on the RF Unit. This modification will only have an effect on two of the relays on your RF unit. (Rl04 and RL05) If you would like to see what it is we are talking about here, down load and print out the following PDF for your files. Our suggestion to you regarding this modification is if you have this modification installed in the rig and it is working leave it alone, go ahead and replace your relays with all 12 VDC relays and leave the modification in the rig. Basically speaking if it works don't fix it. More so recently I have come to the conclusion that this modification may be more necessary then first thought. I recently received an FT-102 back on the bench several months after all it was returned to the customer. At the time initial repairs were done all of the relays were replaced on the RF unit using the 12 VDC relays supplied in the Fox Tango Relay Package. When the rig came back to me after several months in operation, it had a catastrophic failure in the 24 VDC power supply and a defective 15 VDC regulator on the rectifier "B" unit under the transceiver. The receive was basically inoperative due to failure of the power supply board. Now it's hard to say if the parts on the power supply board just gave out on their own or if it had something to do with the new relay installation, one will never know for sure. After repairing the 24 VDC supply and replacing the 15 volt three leg regulator things started to come back to life in the transceiver. However the receiver was still rather erratic and would come and go. A slight push on the RF unit and the receive would pop back in. I wasn't sure at the time if we had an intermittent connection or some other problem, at the same time I also noticed that RL05 was very warm, being concerned about this and not wanting to see a second failure of the rectifier "B" power supply unit I decided to check the voltage on RL05. It was nearly 21 VDC, far more then I would have cared to see at this point. So I decided to go through with the Yaesu suggested 12 / 24 VDC modification as noted in the link above. It basically very simple modification that boils down to putting RL04 and RL05 in series on the 24 VDC rail. You will isolate two points on your RF unit circuit board then run a wire between both of those points. Having done this it seems to have helped considerably and the relays were both at room temperature when completed. I would recommend you look into this modification as a last step to your rely installation. See pictures attached below for guidance in doing this modification if it is not already installed in your transceiver. An alternative way to do this would be to install two 24 VDC relays in place of RL04 and RL05. If you purchase the relay pack from Fox Tango, you will received all 12 VDC relays because this is what the FT-102 was sold with in it's original production and the modification is not all that difficult to do as noted in the pictures below.

I hope this helps you out a bit. If you have any problems please feel free to drop me a note. PROBLEMS ???? Trouble shooting problems during relay installation Many Fox Tango members have written to me telling me how much they appreciate the Fox Tango relay package for their FT-102. I'm really glad to hear this and I thank you for writing. I had only a couple of folks write back with problems, so I would like to take a moment and try to address these

issues. While not highly technical in nature, the replacement of the FT-102 relays should be pretty well straightforward, remove the old, pop in the new, RIGHT? Well yes and no. Let me caution you again #1) Never be in a rush when you're working on your rig. If your tired, put the damned thing down and come back to it tomorrow. #2)Check your work. This means not only to check your soldering and what you are doing in regards to installing the relay at that moment. You need to work slowly and it's wise to check the operation of the transceiver in sections. I highly recommend this. In other words if you change your RL01 in the PA cage, the T/R relay. Put the rig back together and test it after you install that relay. Make sure it all works as before (be it good or bad) just make sure the symptoms have not changed from that of what you started with prior to doing your relay installation job. Then move on to the next board. #3) Again Check your work. Lets assume you move on to your RF Unit and start replacing relays on this board. All the relays go in great! Works looks great and you did a fantastic soldering job. FB~ OM! But you turn on the rig and you have a whole new world of hurt and new problems. Could it be your relay job? Possibly... But let me caution you all of the wiring in the FT-102 is very thin and can be brittle at the solder joint where connected. In the photo below we see a good example of the wiring at the terminal strip that resides right next to the audio board.

When you lift the audio board to get into the bottom of the RF unit. It is very possible that you might break a tiny wire that is tied to the terminal strip right along side the audio board. Thus your symptoms have changed, you think maybe the relay installation job was at fault when indeed you only broke a wire some place. SO USE CAUTION, PROCEED SLOWLY, ALWAYS CHECK THE LAST PLACE YOU WERE WORKING IN SHOULD THE RIG GO HAY-WIRE AND THE SYMPTOMS CHANGE! I can't tell you how many wires and problems I have had to go back and troubleshoot due to my own carelessness, but it happens. Working on an FT-102 this past week I had to replace the DELAY control on the front panel. You talk about a job. The control was working, but the spring mechanism inside the switch went Wacko and the button would not stay in when pushed. I had the front pulled off slightly to the left side finally got the row of controls out and did the job. You would think all would be great! Not so. When I tested the rig last night I could not get power out in the tune position. I could tune up the rig in AM mode and with a whistle in SSB mode everything looked great, but no TUNE. Upon inspection of the mode switch, more time and more work. I found I broke one tiny glass diode on the mode switch. Replaced the diode and everything is back to normal. So the whole point in writing to you today is to remind you over and over again, take your time and check your work. Problems can pop up even for the best technician, if a tech tells you they never mucked up something you know they are not being truthful. It happens to everyone and it can and will happen to you! Be careful and always, always go back to the last place you were working in the rig if the symptoms should change. In this case working with the Yaesu FT-102 it's really very easy to break small wires when removing circuit boards or while doing even a very minor repair.

Lastly, we have all heard it before. For goodness sake! Discharge the H.V. caps in this rig before you work on it. The FT-102 will usually show about 900 Volts D.C. on the plate of the final. The H.V. caps under the rig will pack a real wallop and wake you up if you forget to discharge these things. With an AC shock you can get killed with relatively low voltage 120 VAC or whatever, because you can't let go of the current! In the case of DC, it's not the amount of DC that will kill you. It's that sudden stop when you fall off your stool and your head hits the deck!