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Old 14th Nov 2021, 11:23 pm   #1
murphyv310
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Default Yaesu FT-480R repairs

Hi.
I recently purchased a Yaesu FT-480R cheaply online. The radio was rightly advertised as no transmit. So on Saturday I opened up the radio and had a look and do some tests. When keying the mike it could be heard on my Boefeng. So I paid attention to the PA. This uses a M57713 module, RF was present on pin 1 but no output. Tests showed that pin 2 was devoid of voltage, this was traced back to Q03 a 2SA715C with an open circuit B-E junction, a replacement restored normal output.
There is still a couple of issues which I think is the PLL set up. On tonight's SSB NET, 144.295Mhz it would jump way off on that frequency but be nearly correct on 144.29499, also on 145.475 FM It's 4khz out, other frequencies it's spot on, there is also a slight whistle on receive that varies in tone when you use the fine tune.
Has anyone else had this issue and do you think it's a PLL issue or something else?
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Old 15th Nov 2021, 12:44 am   #2
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Default Re: Yaesu FT-480R repairs

Japanese manufacturers in the eighties and nineties were rather keen on slarting a brownish setting elastomer into the VCO areas of their synthesisers. The stuff is now known to degrade and the products corrode the components underneath, particularly the trimmer capacitors.

Synthesisers can be debugged without too much difficulty once you realise it's the tuning line voltage which gives the most and best clues.

David
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Old 15th Nov 2021, 6:53 am   #3
Terry_VK5TM
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Default Re: Yaesu FT-480R repairs

Frequency jumping - check trim caps, crystals and electrolytic caps (especially low value ones)

Receive PLL whine - welcome to the 70's/80's Yaesu curse, it's a design problem common to a lot of the rigs of that era.

There is a mod for it, search for 'yaesu FT480 mods' and it should show up - I thought I had the notes on this PC but will need to check on another one tomorrow.
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Old 15th Nov 2021, 7:44 am   #4
nemo1956
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Default Re: Yaesu FT-480R repairs

They used rivets to go thought the PCB on many old radios of that age.
I would be worth having a look to see if they used them in the FT480.
I can't remember now.
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Old 15th Nov 2021, 2:35 pm   #5
mastercare
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Default Re: Yaesu FT-480R repairs

Hi as said....i would go through the caps if they are org they can cause a multitude of problems...check all around vco coils for dry joints...
i had to do this on the one i bought......
good luck
paul
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Old 15th Nov 2021, 5:52 pm   #6
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Default Re: Yaesu FT-480R repairs

Hi.
Success!! This morning after warming the radio up I carried out a set up of the PLL, boy was it out. I went through it very carefully on each of the PLL set up's. Later I set the power levels and did some frequency checks that proved to be spot on. Why the PLL had drifted so much is any one's guess.
Now no more whistle and spot on frequencies. Well Chuffed.
Had a QSO between Kilmarnock via the "CS" Central Scotland repeater which is very good with 10 watts into a home made Slim Jim.

PS fortunately the "Glue" is not present on any of the trimmers and it looks as if a couple have been replaced in the past.
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Old 17th Nov 2021, 3:25 pm   #7
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Default Re: Yaesu FT-480R repairs

hi does this rig have ctss fitted cos i thought most repeaters needed it?
cheers
paul

glad your pleased with it....i think it was one of the best rigs in its day...
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Old 17th Nov 2021, 4:28 pm   #8
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Default Re: Yaesu FT-480R repairs

No, No CTCSS

Also the receiver filters on FM are for 25kHz channel spacing. The discriminator is set for deviation appropriate to 25kHz channels, so the reduced deviation now common on the band will sound quiet. The TX deviation will be high, though it can be reduced. Unchanged a lot of repeaters will shut it off.

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Old 17th Nov 2021, 11:31 pm   #9
murphyv310
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Default Re: Yaesu FT-480R repairs

Hi.
I've not had any issues using the tone burst to open the Central Scotland, Dalry and Sanquhar repeaters with the 480.....so far and had a few QSOs too.
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Old 21st Nov 2021, 10:24 pm   #10
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Default Re: Yaesu FT-480R repairs

Hi.
So far the 480R has been performing faultlessly. It runs on my solar system that has a 12v feed into the house via suitable heavy cables. An FT-818ND I had for a few weeks did in no way like the solar system even though its fed from 3x110Ah batteries in parallel. The other issue with the FT-818ND was I had difficulty seeing the display due to its size.
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