[ICOM] PRO III and shut down

[Ken Sands]

Make sure ALL your (HEAVY) grounds go to a (HEAVY) common point and then to
a cold water pipe ground or other GOOD ground system..
It seems you are feeding RF back from the linear to the Pro 3.

My 2 cents,
Ken K8TFD

On Mon, Jul 2, 2012 at 5:59 PM, hamop <k5yy at cox.net> wrote:

>     Hello all ... need some assistance. Never had this situation happen
> before. Today while operating on 20m CW I noted no output, well maybe 5
> watts, and I thought maybe the PS125 had blown an internal fuse for some
> reason. I was running about 50 watts to a Titan amplifier at the time, my
> main setup for 3 years now. Well, rather than tear into the PS125, I put a
> PS85 in line and again a full 100 watts immediately. So thought the PS125
> had truly blown a fuse. Well, after another shutdown to about 5 watts I
> thought the PS85 had also blown a fuse.
>    As one last effort, after about 5 minutes, I returned on the PS125 and
> PRO III and a full 100 watts output again. I found out that if I turned on
> the rig and did NOT hook the PTT line to the Titan, all seemed to be OK
> with no “shut down”.  But, even keying the amp with an EXTERNAL foot switch
> and trying to drive the amp, bang ... again just 5 watts out, but it
> returned to 100 watts after another 5-6 minutes.  Is the PRO III or PS125
> and PS85 ( unusual for both to do it) heating up inside causing the
> shutdown by some quirk feedback from the Titan amp?  Seems like if just
> barefoot straight to the antenna, I can transmit 100 watts as normal with
> NO shutdown. Puzzling to me for sure. Appears since same thing happened to
> the PS 125 and 85 that both should not have developed the same ‘shut down’
> issue. That leaves me wondering if my PRO III finals are overheating some
> how?
>   Thanks for any suggestions.  Receive is fine the entire time. If I shut
> down the PS and PRO III for just 3-4 minutes, the output may drop quickly
> with about 20 seconds of CW and the longer units are off , the longer the
> power stays up.
> 73
> San K5YY
>
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