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[russ at wxqa.com: RE: [wxsig] T238+ Characters and Heat...]

Will Beals will at beals5.com
Sat Sep 30 02:37:30 UTC 2006


Scott:

OK on Poly-Sci, I are an engineer! :)  It is surely safer for you to fiddle
with engineering than me with politics!!!

Interesting that the hot regulator problem has gone away!  That means either
something has been irreprably broken (not so good news) or that maybe you
had two issues, one transient problem causing the hot heat sink and a more
permanent one failing to drive the LCD.  I'd prefer to assume the latter and
help you along those lines.

Do all the steps below without the weather head plugged in:

With all voltages checking out, nothing getting too hot, and the LED doing
it's regular blinking it is clear that most of the kit is OK.  In particular
the CPU does appear to be pretty happy, running OK enough to give other
signs of life.  This and your voltage measurements confirms the CPU,
Oscillator, and MAX232 chip.  You are also confirming the power to the LCD
is OK.  I do want to check that by Normal LED blinking you mean three fast
blinks on power-up, a pause, then regular beats once a second.

One thing to double-check is all of the soldering and connections between
the CPU and the LCD.  I am hoping that there may be a not-so-great solder
joint or bent pin on one of those seven lines between the two devices.  If
one of them were intermittent, that would be a tangible explanation for it
working once, then not working afterwards, with the plugging in of the
weather head being a bad coincidence.  In addition to the seven digital
lines, also look at the LCD contrast voltage (V_LCD on pin 3).  It should
change when you adjust the potentiomenter and should be a little less than
0V when adjusted correctly, I think about -1V or so.  If it isn't, then you
have an issue somewhere around the potentiomenter.

In the off chance there may have been a partial corruption of the code in
the CPU, one thing to see is if you can boot up the CPU into the code
downloader.  With the unit powered up, press and hold both Up and Down while
hitting the reset button.  If you see text, the code has been corrupted.  If
you still see black squares, it is not a firmware issue.  BTW, to my
knowledge this has never happened, so it is pretty remote.

Let me know how the debug goes.  I am generally around this weekend, but
then will be offline starting Monday for a week.

will

-----Original Message-----
From: AD7MI [mailto:scotthedberg at msn.com] 
Sent: Friday, September 29, 2006 7:35 PM
To: will at beals5.com; 'TAPR Weather Station SIG Mailing List'
Subject: RE: [russ at wxqa.com: RE: [wxsig] T238+ Characters and Heat...]

Will,

Ok - I pulled the T238+ out of the box again and did some testing with the
modem detached.

(1) The regulator no longer gets hot.
(2) Still have the black squares.
(3) "Heartbeat" LED still acts as described when the power is applied.
(4) Did I plug the LCD module in one pin off?  I don't believe so, but I
guess it is possible.
(5) No other components are hot.
(6) I re-did the +5V checks listed on page 9 of 11 and +5V, >8V, and <-8V
checks on page 10 of 11.  All measurements are good.
(7) "try measuring the +5V rail with the problem" - I'm not sure how I would
do this.... sorry, poli sci major here - guess I should have picked better
electives in school.

Do I need to order another kit and give it another go?

73 Scott AD7MI


-----Original Message-----
From: Will Beals [mailto:will at beals5.com]
Sent: Wednesday, September 20, 2006 8:58 AM
To: ad7mi at arrl.net; 'TAPR Weather Station SIG Mailing List'
Subject: RE: [russ at wxqa.com: RE: [wxsig] T238+ Characters and Heat...]

Scott:

Uh-oh, this might not be good.

I gather now that you have the hot regulator and black squares no matter if
the weather head is plugged in or not.

Any chance the LCD module was plugged in one pin off when you re-assembled
things?

Are any other components getting hot?  The backlight resistor will
(normally), but nothing else other than the regulator should be getting even
warm.

Also, try measuring the +5V rail with the problem, then sequentially remove
chips (CPU, MAX-232, LCD).  I'm hoping one of them may be the issue and once
you unplug it the +5V will go back to normal.

I'm in between trips, so may be silent until Saturday morning.

will

-----Original Message-----
From: wxsig-bounces at lists.tapr.org [mailto:wxsig-bounces at lists.tapr.org] On
Behalf Of Scott Hedberg
Sent: Monday, September 18, 2006 2:13 PM
To: wxsig at lists.tapr.org
Subject: RE: [russ at wxqa.com: RE: [wxsig] T238+ Characters and Heat...]

Adjusting the potentiometer makes the black squares more black or less
black.  I had initially adjusted the potentiometer during the setup and the
text was very readable before.  I was also able to input all the parameters
into the T238+ after I attached the weather station and did confirm that the
display was showing me temp, wind speed, and wind direction.  The heat sink
was only warm to the touch.

I powered back down and then attached the radio interface (DB9 on the modem
board), powered everything backup and got the black squares and the very,
very hot heat sink.

I disconnected the radio interface, powered up, and am still getting the
black squares and very hot heat sink.  The heartbeat LED still does what it
should be doing.

I disconnected the modem board, powered up, and am still getting the black
squares and very hot heat sink.  The heartbeat LED still does what it should
be doing.

Did I accidentally short something or otherwise fry one of the components?

73 Scott AD7MI




  -----Original Message-----
From: Beals, William [mailto:William.Beals at echostar.com]
Sent: Sunday, September 17, 2006 2:58 PM
To: russ at wxqa.com
Subject: Fw: [wxsig] T238+ Characters and Heat...

   Scott:

   The regulator does get hot as Mike points out below. This should be the
case if the weather head is plugged in or not. Lower main supply voltage is
the best "cure".

   A good experiment to try is hot plugging and unplugging the weather head.

It won't hurt anything. If plugging in the head makes the LCD go from normal
to black squares, the something fishy is going on. It looks like +5V is OK
as the cpu is still working. The LCD also relies on a -9V supply from the
MAX232 to generate the bias/contrast for the LCD. Plugging in the weather
head should not affect it, but you may have a soldering error or something. 
Check the bias voltage before and after pligging in the head to see if this
is the cause or a wild goose chase.

   It may be an obvious question, but just in case: You are plugging in the
weather head into the "telephone" connector, not the serial port via the
AAG-supplied adapter, right?

   Response from me is a bit slow as I'm out of the country and have only
intermittent access to personal email and need a proxy to get info on the
reflector. Thanks Russ!

   will
   ------Original Message------
   From: Mike C.
   Sender: wxsig-bounces at lists.tapr.org
   To: TAPR Weather Station SIG Mailing List
   ReplyTo: TAPR Weather Station SIG Mailing List
   Sent: Sep 16, 2006 9:50 PM
   Subject: [wxsig] T238+ Characters and Heat...

   Scott,

   Try adjusting the contrast potentiometer on the T238+ board. As you go
   through the adjustment range the blocks should become
   characters of info. As far as the 7805 5volt  1 amp regulator getting
   HOT. If you are running it on 13.8 vdc it will run hot.
   I had the same problem. I decided to run an 8 volt regulator 7808  in
   front of the 7805 to distribute the heat, between the two devices.

   Good Luck!

   Mike C.

   KA6DAC


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