[Elecraft] Re: PA HOT

[Joe Squarzini]

Dominik, thanks. Makes a lot of sense. Looks like Eric and Wayne need to 
come up with a permanent fix so that we aren't resetting TPA. I received a 
lot of replies so many others must have seen this problem.   Thanks and 
hope all is well . . .73   Joe



At 12:56 PM 5/14/03, Dominik Bugmann wrote:
>Joe, Rich,
>
>I have/had the same issue here and I posted the findings a few weeks ago on
>this reflector
>http://mailman.qth.net/pipermail/elecraft/2003-April/053270.html.
>What I figured out so far is:
>The temperature meter is Q3 and mounted right next to Q1 and Q2. The voltage
>drop from B to E is roughly 0.6V and varies over temperature. Fortunately
>this effect is very limear (over a high temp range) and much better compared
>to a PTC or NTC. Unfortunately the change is only a few mV/C. As you can see
>on the page 61 in the manual Q3 is directly connected to U1/PIC16C72 where
>they measure the voltage of Q3. To measure a very low level (0.6V) directly
>with an A/D converter is not an easy task and I assume that the reference
>level within the MCU (U1) is also temperature dependant. When I switch on my
>KPA100 I read 8C which goes to 20C within a few minutes. Q3, U1, ..the whole
>KPA100 heats up a bit. Nevermind this is not a big issue for KPA100.
>Unfortunately there is a softwarebug which occurs as soon as the reading is
>below 0C. One would expect a negative number but it is represented as e.g.
>255C (underflow of an 8 Bit counter). The controll software for the fan and
>"Hot PA" only looks at this number (e.g. 255C) and concludes it must be hot
>out there. At least this is my understanding of the whole issue.
>My workaround so far: Check the tPA reading of the KPA100 and (re-)adjust if
>needed.
>
>73 de Dominik, HB9CZF
>
>
> >Ditto on what Joe has said. I had my fan on continuously and I check CAL
>tPa
> >and temp wall 200C. Reset it and no problem.
> >Rich
> >KQ9L
> >
> >On 5/13/03 7:04 AM, "Joe Squarzini" <k4aa@verizon.net> wrote:
> >
> >> Carter, I had the same problem. I found that the PA Temp setting had
> >> drifted inexplicably to 256 deg. I reset the parameter to room temp and
>so
> >> far it has not happened again. I suspect RFI. No proof however. My K2/100
> >> is mounted in a separate EC2 enclosure along with the KAT100.   Joe
> >>
> >> Joe Squarzini, Jr.
> >> K4AA
> >>

Joe Squarzini, Jr.
K4AA

Home      (703) 759-4943
FAX        (703) 759-0656


--- StripMime Report -- processed MIME parts ---
multipart/alternative
  text/plain (text body -- kept)
  text/html
The reason this message is shown is because the post was in HTML
or had an attachment.  Attachments are not allowed.  To learn how
to post in Plain-Text go to: http://www.expita.com/nomime.html  ---