[FT100] Re: [Yaesu] YAESU FT 100

[Robin Midgett]

My FT-100D was primarily used for FM repeater operation and 
occasionally HF/6m SSB, always mobile. One day the HF PA started 
drawing way too much current..the rig was so hot I couldn't keep my 
hand on it. I had done the fan mod to keep the fans running 
continuously, as recommended by other users who noticed the rig tends 
to run hot.
The problem (as I understand it) is that the PAs draw current whether 
in use or not, and there isn't enough heat dissipation to keep the 
rig cool. Being MOSFETs, the PAs can easily slide into thermal run 
away, drawing more current as they heat up until they destroy themselves.
I suppose I'm somewhat fortunate in that my case involves the HF PA, 
not the now discontinued V/U PA devices. At ~$80 each, the HF PA 
devices are expensive...but at least available.
V/U SSB does take place...but not nearly to the extent as HF. The 
January ARRL VHF/UHF contest is just a few weeks away...try it!



At 09:24 AM 12/14/2005, Darrell Drake wrote:
>True John, but I was assuming FM transmissions on VHF/UHF as in 
>simplex or repeater operations. I never thought of SSB transmissions 
>on the VHF/UHF bands.
>   In my 22 yrs. of hamming, I've heard very few SSB VHF/UHF 
> stations. It would nice if it occurred, but it seems, in this neck 
> of the woods at least, VHF/UHF means FM through repeaters. As the 
> old saying goes, "you can't teach a Heinz pickle nuttin' ".
>
>   In keeping with the original post on this topic, I still maintain 
> if one keeps the power down, again thinking key down FM, the 
> VHF/UHF finals will have some "breathing room" and probably last 
> for ever (however long that is!!)
>   At least, that's my theory.
>   Cheers for now & Happy Holidays
>   Darrell,
>   VA3DG
>
>John Geiger <ne0p at lcisp.com> wrote:
>     But average power on VHF SSB would only be 20 watts or so, and 
> average power on UHF SSB would be around 10 watts, both less than HF.
>
>73s John NE0P
>
>   ----- Original Message -----
>From: Darrell Drake
>To: Yaesu at mailman.qth.net ; ft100 at yahoogroups.com
>Sent: Wednesday, December 14, 2005 1:30 PM
>Subject: [FT100] Re: [Yaesu] YAESU FT 100
>
>
>Hi Nick....
>I think you've hit the nail on the head by not running the radio at 
>full power, at least on the VHF/UHF bands. HF (ssb) wouldn't matter 
>if it's set at full power because 100 watts would only be at peaks, 
>with the average being around 50-60 watts.
>I've had my radio going on 3 yrs. now and only run it at about 5-10 
>watts on the VHF/UHF frequencies. It runs flawlessly and cool as a cucumber.
>
>
>"nickn9hno at netzero.com" wrote:
>Hello to the group,
>I have read about the problems with the ft100 vhf/uhf transistors 
>but I have not heard what causes the falure. I have a ft100 that 
>works perfect and never had a problem with it.
>Can some one tell me what the falure is due to and what can be done 
>to avoid having this problem.I dont run my ft100 on full power ,I 
>run it at about 70% on hf and about 50% on v/uhf.
>THANKS
>NICK/N9HNO
>
>Cheers...
>Darrell,
>VA3DG/VE3DDG
>
>
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Thanks,
Robin Midgett K4IDC
VHF+ Glutton
God Bless America, in God we trust.