开云体育

Bumping the thread up:

I have the latest flrig/fldigi/hamlib sources on this system (which I'm using to post) and have successfully compiled all three programs. I've also written and tested flrig drivers for the IC-751 and R-71. Let's have a crack at more FT-980 stuff.

The only problem being that the PC and gear under test is the upstairs office/shack, and my '980s live in the main shack in the basement. So I'll have to duplicate PCs down there. LOL.

73 - Fred, N8YX

I believe they are the R16 and R18 shown in the parts list as metallic film, 1W, 1.5 ohm.? They are right next to transformer T02.? They appear to run in parallel to C27 and C29 caps.

73 Bob N9IB

L05 it is not missing. Just changed place :)

L05 feeds Q01. In the schematic takes from 13.5V line. That means Q01 has collector voltage all the time.

The ?factory? mod changes L05 to feed from TX13.5V (only in transmision) you can see it in your radio feeding with a YELLOW wire that takes from the regulator Q06 input. A post in which the yellow wire connects with the red TX13.5V. Therefore L05 in somewhere in the air close to Q01 ferrite collector coil.

I guess you have not replaced a new L05 in the position of the schematic without removing the yellow wire, otherwise you had connected together the 13.5V and TX13.5V lines.?

Maybe they changed L05 to TX13.5V to avoid Q01 oscillating in reception. In TX it is piloted by RF signal.

Can you be more specific about the resistors that smoked?

73 Frank EA1FC

Hi EA1FC,

I replaced the C20 which had blown and the C18 like you did.? I got some 10uF, 16V tantalum caps from Mauser Electronics.? They are yellow and about the same size as the originals.? I also noticed in your picture that the L05 inductor that shows on the schematic is missing. Mine is that way too.? I put mine back together and it smoked again.? This time I can see two burnt resistors by the T02 transformer. (See picture)

73 N9IB

I thought I had uploaded the 10uF capacitor. I placed a plastic screw in Q01

This capacitor is specially prone to fail. 4 that I know up to now. There are many more in the radio, bur this one besides being of higher voltage is the one that fails. With different color, maybe another maker

73 EA1FC

Has anyone in the group ever had a problem with the detector diodes in the Fwd/Ref Power circuit (CM Coupler) failing? Seems that the SWR functions on two of my '980s are inoperative, though the Fwd Set (and both meters themselves) work fine. Only things I can think of which would cause a failure is high near-field energy caused by multi-transceiver operation, or nearby lightning strike.

Regardless, I have some 1SS97s inbound.

Other causes of the malfunction?

73 - Fred, N8YX

I was just re-reading this thread and noticed your comment about the missing screw in Q01.? Mine had a plastic machine screw in the hole but no nut was on the screw. I took the screw out before taking the picture. You can also see my blown C20 capacitor.

73 N9IB
?

Hi Robert,

I finally got this radio working after re-reading the manual and adjusting several settings.? It worked for one day and blew a capacitor in the PA unit.? The capacitor is brown and the schematic lists it as 10uF and .50wv.? In the diagram it also has a T in parentheses like (T).? Is that tantalum?? I want to make sure I get the right one to replace it.? Any help or suggestions would be appreciated.

73 N9IB

Finally my FT-980 is more or less OK, the only strange thing is temporal. LSB beat is wavering, I guess the PLL is not locked, manual tells to wait 5 minutes before adjustment and in my case is around 10 minutes. And voltages are low.

I managed to adjust the 30MHZ to 4Hz error, and now all is close to perfect. Display exactly on frequency and listening to AM broadcast in SSB, voice? tone or music does not change when I change LSB and USB. As I have a 2.1kHz wide filter in 455 FI, if it is OK, it means it is almost perfect.

The only repair after a long seach, and besides adjustment, has been the tantalum capacitor in PA Q01 collector, 10uF/25V it was shorted pulling TX13.5V to 3V and activating the overload of the 13.5V PS. It had the mod to feed PA Q01 from TX13.5V instead from general 13.5V

Regarding PS heat, I feed the radio with 200V, with input wired for 234V, and voltages seem to be OK, reports are of excellent modulation, and fan never comes in in RX

I had a look at my FT-ONE with a similar PA and all seem to be OK. Tantalum in PA Q01 collector is 10uF/16V. I note that the only tantalum catastrofic in these PA that I have met have been of the 25V type, in short ALL I have seen, while none of the other 10uF/16V have been damaged, and that counts about 20 times more. So without any real reason I would recomment check the FT-980 radios and similar, and change PA Q01 collector tantalum capacitor in case it is of the 25V type. It sounds silly but maybe the 16V capacitors (all brown color) are more reliable than the 25V (blue or red in what I have seen)

I think FT-707, 107, 980 and ONE have a very similar PA.

After I commented with a friend about the tantalum problem in PA predriver, he look at a FT-107 bought in a lot (interested in the tuner FC-107) he look in the PA and found predriver tantalum blasted too.

PA in these radios are very very similar.

In the FT-107 it is 16V (blue), and in the FT-980 they changed it for 25V (red), the only 25V tantalum on the PA the remainder are 16V (brown)

Curious that Yaesu changed voltage rate in the FT-980 to 25V. Maybe had some feedback from other radios. I guess FT-707 is similar. And there are the first transistor finals radios.

73 EA1FC

Tested with 200V wired for 234. I have small changes of voltage, I tried with 195V but sometimes mains voltage lowered and I was told that the signal worsened.

So I leave for 200VAC in reception. The variac is 500VA, so a small drop of 3V is normal.

Now PS and PA have similar temperatures in normal use, and cooling fan stops some 3 minutes after a long transmission. The PS temperature stabilises in 41?C (22?C in room) and the fan never comes in reception.

Having lower AC voltage in the PS has another advantage. The conducting cycle in the rectifier is longer, needed to smaller difference in voltage between input and output to capacitors. As the power is R x I2 (squared) if the rectifier conduct double the time at half the intensity for the same Culombs to charge capacitors, the power dissipated if rectifier halves. And at full power (12A) the difference may be 5/7W less in rectifier (1,2V loss)

Adding all it may come close to 70W less in transmission. A difference. Main advantage is for the PS.

73 EA1FC

I tested with a 500VA Variac that drops about 3V when transmitting.

185V in receive, the FT-980 24V show voltage right in the middle of area, but fluctuates a bit inside range when transmitting FM full power.

190V in receive and the voltage meter does not move when transmitting FM full power. The Variac drops 3V. So I decided to leave it in 193V so it drops to 190V when transmitting FM full power (I guess this is not advisable)

Of course SSB gives full power.

I have not done detailed calculation, but I guess this halves the heat dissipated in the PS. Now I see that temperature in PS and PA are more equal.

When I consolidate tests, I will have two options, an autotrafo 230/190V that is the best solution or somerhing like a 15 Ohm 100W resistor in series with the mains, that would not resolve the overheating in receive, but help in transmission.

But the radio beast says that is a 530VA (that I doubt to produce 100W out) if so there is the real proof of the heat. 530VA IN >> 100W OUT not a very ecologic radio.

I have not tested with a local OM to see effects (if any) in the quality of transmission.

73 EA1FC

Super topic.

I think the PS is not well designed. Specially too much voltage in AC area.

So I will try other approach. To reduce the heat, because the PS is always hot, and worse cooled than the PA that runs reasonably cool

A silly calculation tells me that 200V should be enought with primary at 234 (I guess that less that 190 will be the figure). So I am going to try.

Above all because the biggest risk ist failure of PS letting full voltage to PA, that wold be destroyed inmediately.

So after 40 years... I will try.

73 EA1FC

I read the service manual, I say I look at the schematics, and found the trimmer. As I said i have no idea about PLL but inside the can there is a transistor with a thermistor in the emisor in parallel with a resistor. And my problem disappears when radio is hot.

So I decided to accelerate the process. Took a soft hair drier and pointed to the holes for TP and TC. And the "time to normality" went almost to zero.

So I guess the no voltage in TP and strange sound in LSB has to do with this transistor not oscillating, or something similar, as I said I have no idea about PLL neither this transistor that does not look as a transistor in the schematic hahahaha

The service manual says to avoid touching the trimer capacitor until 5 minutes from cold start, coming from 1h cold 15/25?C. After some minutes I get voltages, but 50% what the manual says. around 3V in USB, 1,5V LSB, Witdh according to manual.

I dont know what is going on. Supposing this "malfunction" is not normal, I guess it will be due to low voltage somewhere so the Thermistor takes a longer time to reduce resistance. I helped with the hair drier. I did not want to put too much hot air through the holes as my grand dad told me too much heat is not good for semiconductors.

I glued the 2nd FI FT 455kHz filter in the metal cover of PLL unit, and wired it to FI unit. So it is not so easy to lift the cover.

I guess this large cover just pulls up, held by some presure in the sides. I may try.

In the meantime I go on thinking next step. I think it will be? a problem of voltage, a bad resistor or capacitor.

Maybe I manage to catch a friend that says he knows about PLL.

73 EA1FC

To N9IB
Your problem it is hidden in my former title, and maybe other members will not find it, maybe you should open other thread. I have opened a new thread regarding malfunction in the first 10 minutes after switch on the radio.

I asked about reception in GEN because the band filters in RF unit for HAM or GEN are different. And the electrolytic capacitors in the HAM filters have given problems sometimes, so the first thing would be to discard the filters. As you say the lack of reception is similar in both modes, the problem it is not in the filters themselves. Once filters discarded, comes teh voltages that selects the filters.

So you have to check J10, J11 (HAM), J12 (GEN/HAM) and J13 (GEN) just pull them and push them. J13 should have 13.5 in the selected band and 0V in the others. J10, J11 0/4V, and J12 HAM/GEN 0.7/9 and 0.7/8. I am a bit lost in the logic and uP. But I think I am right. May someone know better.

Another problem is than the band filter is OK but the logic HAM/GEN is opposite in this case.

But you can check in the filters that the diode are ON, even if when testing the reception is affected by the voltage testing

So I think this is the first thing to do.

I dont know how to analyse the logic that generates those voltages, uP and so on. I am old and I manage better tube radios hahahaha

But first thing is to cleac/ check voltages in those connectors, before I told you to lift them and put them to clean them. But it is easy to check that the correct voltage arrive to the band, and.... no voltage to the other bands.

Maybe you should copy this text if you find it interested, for your new thread on your problem. Here is hidden for most.

I initially said it only received in 80 and20 meters.? It does in fact receive on other bands but only for very strong signals.? It's like the RF gain was turned down but it's not.? The S-meter never moves either during reception.

N9IB

My FT-980 is series 04. So I guess all service notes needed in early versions were done.

After fixing the PA, next day I found that LSB reception was... strange, like added AC, tremolo when listening CW in LSB mode... in short very bad. All other modes were OK as much as I remember. After some 10 minutes LSB reception was normal, and I made a one hour QSO with very good reports on my modulation, I received all OMs with no problems. But the problem is there. Only in LSB and only the first 10 minutes.

I read about and thought about TC01 in PLL unit. A well known candidate. So I checked as per service instructions. USB, Witdh CCW, and no voltage at all. Whatever I do cero voltage in TP. The radio was receiving OK in USB, but still horrible sound in LSB. I was sure I was doing something wrong, and check and check and changed meters, they show 0,00V.

Until it got warm. And LSB sound became normal. Not a believer, I rechecked voltage in TP, and I had voltage, but out of range. USB and WIDTH CCW about 3V. LSB and WIDTH CW 1.5V. Exactly half what the manual says (6V-3V/4V)I hope my meter is OK. That is why I opened a new thread, works after 10 minutes and voltage ratio USB/LSB 2:1 is almost exact. Just it does not exist in cold and when appears is half the normal value.

As I told in the PA problem thread this radio has been sleeping for more than 25 years. And as today I have not realigned anything. So I guess I should do something with my limited means.?

BTW I hope the large metal cover of PLL/VCO units lifts just pulling. I dont have good test equipment, but I have a frequency meter, good ceramic trimming screwdrivers, and a RF probe I have never used. And null experience in PLL or similar.

Neither the user manual nor the service, explains the signal path or function. In my old FT-101ZD the operation manual described with detail how the radio worked.

Well, if I wait 10 minutes before I use it in LSB it is a nice radio. But I would like to understand what is happening.

73 EA1FC

I have added some photos related to the text. Photos have a short name

73 EA1FC

radio_ozu <javier_ebay@...> added the album radio_ozu: Some photos from the text discused. Most with explanations