Yaesu FT990

[WT8E]

I have started a new post as the older one is over 60 days old.  My 990 just went belly up with no readout and a loud buzzing sound.  Meter light works but all buttons do not function. I attempted a reset but still have the same problem. I pulled the board with the lithum backup battery and it reads 2.92 volts out of a 3 volt battery.  Is that enough for the radio to function?
Also is the battery soldered in? It seems the top clip of the battery holder is very tight and I can't tell if it is soldered.

I called Yaesu and they do not offer and any repairs or support due to the age of the rig.  The radio was manufactured from 1991 until 1999.  Reading some of the posts many refer to the CPU and if that is the problem then its curtains for the rig.

The rig has been great and a pleasure to operate, I hope this is not a lost cause.  It worked FB earlier today and then when I turned it on later I got the results described above. It is now 4:48 PM and I just tried it since its been off for about 5 hours. The readout came up all "0's" but still have the same buzzing noise with nothing else working.  I tried it again a few minutes later and same noise but this time there was no readout.  Any help will be greatly appreciated.

[N5VTU]

Have you tried contacting any independent repair shops?  They can continue to support older rigs after the OEM quits because the smaller shops usually have donor radios to cobble parts from if needed.  It might be worth a shot for such a nice vintage rig.

Good Luck,
Stephen
N5VTU

[WB2WIK]

Is this the model with the built-in AC power supply?

If so, did you check to see if the power supply is working?  Sounds like maybe it isn't.

[WT8E]

Yes to both questions. ARS in Portland , Org. will work on the rig with my understanding that if its the CPU then they would have to find a donor rig for that part.  So, as I have continued to read and research I have reinstalled the board back in the rig. Still having the same problem but now the readout will stay on with "0's" across the readout. I found a post about using a "'Hard Start" by turning off the battery switch and then trying the radio.

I turned off the battery switch and the rig powered up on 7.000.00 and the VFO worked OK. I rolled it up to 7.125.00 and then turned the rig off.  I turned it back on and got the first reading of 7.000.00 and the VFO still works fine. It looks like the backup battery has failed so a replacement will be next.  I will call Yaesu on Monday to get one. I hope I am on the right track, it would appear so at this time.  I still don't know if the battery is soldered in or just a very tight fit. Has anyone changed the backup battery, still looking for any help on that. The noise is also gone, not sure why, the volume control had no effect on the noise. I guess the 2.92 volts is just not enough voltage, somehow the low battery must have an effect via it trying to remember the last Freq. for the rig to power up.

Thanks to all  & 73's
Walt
WT8E

[KE3WD]

If you read 2.92 VDC on the memory cell while in circuit, it is fine.  A drop of 0.8V is NOT going to stop the show. 

Your problem sounds like a power supply issue, either a dried out electrolytic or two or possibly a flaky three-terminal regulator or pass transistor, or both. 

Bad CPU is only prolific problem on internet forums.  My testbench experience with many different types of gear tells me otherwise, the CPU doesn't fail all that often actually. 


73

[WT8E]

KE3WD, thanks for your input. I have the rig back in line and here is the situation as of now.  It still powers up on Band like 7.000.00 with no noise like before. The backup battery is still switched off. The antenna tuner will not automatically tune, have to start the tuner and it only stays in for a very short time, usually not reaching a match.  The red wait light comes on if a transmit is attempted. Given enough manual starts with the tuner it will tune and get a match.

Reading the manual it states that the automatic antenna will store up to 39 matches per band if I understand it correctly so I assume the backup battery also controls the memory for the tuner. I don't want to become a pest with all the questions but I surely do appreciate all the help.  The rig is AC/DC capable and I have only used with AC power. I have a 25 Amp power supply that I could hook up if you think that would help.

Turn around repair is from 6 to 8 weeks if all goes well, of course that is still an option.
Tnx
Walt

[WT8E]

Well, maybe this will be the last post on this problem. I was gone for the weekend and of course left the rigs off. This morning I turned the battery switch back on and fired up the rig. Everything now seems back to normal with full output and the auto-tuner functioning as it should. Before I left this past weekend as I think I had stated I did a "hard reset" on the rig. This is done with the battery switch turned off. Some suggestions were to leave it off the air for awhile, which was accomplished while I was out of town.

With the battery switch back on in changing bands the auto-tuner finds a match and keeps it in memory. I have gone through all bands and it appears to be working well now. If I shut the rig off it comes back on tuned to the last freq. I was on and if I change freq enough or change bands it retunes immediately.

So taking your advice, KE3WD , I will not change the backup battery as it appears it has enough voltage to function propetoy. Not sure of the date of manufacture of the rig but the battery has never been changed since new.  I will have to check the serial number to satisfy myself now on how old it is. As for now I will leave it alone, maybe the problem will be back tomorrow, we shall see.  Thanks ot all for the help and suggestions.

73
Walt

PS; The trip out of town was to see our 9 year old Grandson wrestle in the season tournament, he finished 2nd in his class with 18 schools having teams.  It was a long day but was very nice to see him do so well, plus Sunday was Grandmas' birthday so it was a nice present for her.

[KE3WD]

From your reports it sounds like there is a switch placed between the backup battery and the memory circuit. 

I would suspect dirty or dry switch contacts on that switch, a very tiny spritz of DEOXIT or equivalent into that switch and while the good stuff is still wet, throw the switch back and forth 10 to 20 times to get a mechanical cleaning action on its contacts. 

Then keep an eye on things for any possible repeats of the failure, but odds are fairly good there won't be. 


73

[WT8E]

Well with all the help I received here the 990 continues to function properly. The last item being the date of manufacture to get an idea how old the rig is and how long the original backup battery has been in use.  The serial number is 3F230018 so if I understand the breakdown it goes like this.

3 =        1993
F =        April
23 =      The lot #
0018 =   Serial # in the lot

So it looks like the rig was 0018 of lot # 23 manufactured in  April of 1993. The original battery is still in place. It has been a great learning experiance and tnx to all.
73
Walt