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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment. |
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20th Aug 2018, 11:55 am | #1 |
Triode
Join Date: Aug 2016
Location: Christchurch, Dorset, UK.
Posts: 11
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Yaesu FT480R faulty
My trusty FT480R of many years has suddenly stopped working. Although the display lights up and the digits change as you tune and there is noise out the speaker, it won't receive any signals or produce any power output.
This really smacks of the LO not functioning confirmed by lack of any ~133Mhz present when I "sniff" with my scanner. The LO is a complex 3 VCO system and as far as I can tell perhaps 2 of the 3 are functioning. Perhaps someone has seen this fault and can short circuit my fault finding for me? Regards |
20th Aug 2018, 1:27 pm | #2 |
Heptode
Join Date: Nov 2009
Location: London, Ontario, Canada
Posts: 675
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Re: Yaesu FT480R faulty
You can download the service manual from here:
https://www.manualslib.com/download/...u-Ft-480r.html It has a detailed "fault tree", a troubleshooting flow chart. I guess you need to go through that. Good luck, Peter |
20th Aug 2018, 1:33 pm | #3 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,903
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Re: Yaesu FT480R faulty
Japanese rigs of this period had problems with trimmer capacitors being rotted by the gunge they poured around to stop microphony.
A complex synthesiser is just a lot of simple circuits flying in close formation. Your approach of finding which loops are running and on frequency with a receiver is a very good starting point. You'll likely come to the point where a scope is needed. My old FT480's kicking around in the shack. I don't think it's seen power in 10 years. Must give it a try. Quite nice radios. David
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20th Aug 2018, 5:22 pm | #4 | |
Triode
Join Date: Aug 2016
Location: Christchurch, Dorset, UK.
Posts: 11
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Re: Yaesu FT480R faulty
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20th Aug 2018, 9:46 pm | #5 |
Heptode
Join Date: Sep 2004
Location: Preston, Lancashire, UK.
Posts: 632
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Re: Yaesu FT480R faulty
I’d check all the voltage rails round the circuitry are in tolerance. If it's anything like the Kenwood I've just brought back to life there is a lot of electrolytic cap decoupling and they go out of spec.
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23rd Aug 2018, 10:00 am | #6 |
Triode
Join Date: Aug 2016
Location: Christchurch, Dorset, UK.
Posts: 11
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Re: Yaesu FT480R faulty
I checked the 3 PLL voltages against the manual and they were quite far out so I have reset them all to the values stated and it all seems to be 100% again. Quite why they were all so far out though remains a mystery.
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3rd Nov 2018, 6:16 pm | #7 | |
Triode
Join Date: Aug 2016
Location: Christchurch, Dorset, UK.
Posts: 11
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Re: Yaesu FT480R faulty
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