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[wxsig] Help with T-238 failure

John Koster w9ddd at tapr.org
Fri Jul 1 03:41:06 UTC 2005


Will managed to find a 'hot spot' in London to reply to me on another 
subject.  Below are his comments related to the 7805 failure.

------------

On the gentlemen with the bad 5V bus, all I can offer is that the micros
are pretty tough. I've abused a few in my life and even though the part
was tortured way out of spec there is a decent chance it survived. The
oscillator is clearly a concern. A quick and dirty check for the clock is
a voltmeter in DC mode. If you see 0V or 5V you are pretty certain things
are blown. Somewhere around 1.5V to 2.5V, at least you stand a chance of
the clock being OK.  Only suspect the LCD after getting the CPU heartbeat
working and the LCD still doesn't work.

will 
------------------------------
Message sent using thumbs on a PDA.
Sent wirelessly, so recycled elecrons
are also 100% local content.


On Thu, 30 Jun 2005, N5ZTW Bill wrote:

> I also have spare MPU's. If it's the MPU I can try and get a failure report 
> on it. My system keeps locking up and it may be the MPU also. I'll look at 
> it this weekend. I work for Freescale Semiconductor (Former Motorola) and 
> know the guys in the group that supports the chip. (some are hams). We 
> reside in the same campus so it may be worth have them autopsied.
> Bill N5ZTW
> ----- Original Message ----- 
> From: "John Koster" <w9ddd at tapr.org>
> To: "TAPR Weather Station SIG Mailing List" <wxsig at lists.tapr.org>
> Sent: Thursday, June 30, 2005 9:19 AM
> Subject: Re: [wxsig] Help with T-238 failure
> 
> 
> >I have spare MPU and RS232 chips here.  I don't for the 32MHz oscillator
> > module, since it's a different version for T238+
> >
> > On Wed, 29 Jun 2005 Sct599 at aol.com wrote:
> >
> >>
> >> Hi John:
> >>
> >> Thank you for the response.
> >>
> >> LCD: When I initially found the unit after the failure, the display had
> >> random unintelligible blocks of pixels. These pixels would change in 
> >> response to
> >> pushing the "Select" button. After subsequent power ups, the display is 
> >> blank
> >> of  any pixels. The back light remains functional. With it showing the 
> >> random
> >> pixels  initially indicate that it may have survived the event?
> >>
> >> Crystals: I will check these as soon as I can and report back. Believe it 
> >> or
> >> not, my scope is only a 5Mhz!
> >>
> >> PC port: I had thought about doing this but did not since there was no
> >> "heartbeat" LED activity. Heartbeat LED checked out OK. Should I give it 
> >> a try
> >> anyway?
> >>
> >> Thanks again,
> >> Scott
> >>
> >>
> >>
> >>
> >>
> >> In a message dated 6/29/2005 10:43:26 A.M. Mountain Daylight Time,
> >> w9ddd at tapr.org writes:
> >>
> >> Any  indication that the LCD module survived?  For some reason that and 
> >> the
> >> crystal modules would be the first suspects on my list.  You should  be
> >> able to talk to the unit without the LCD though via the PC port.
> >>
> >> I'd start by verifying the oscillator works with either a scope or  logic
> >> probe that's good to 32MHz.  Nothing happens with the 32MHz  clock 
> >> working.
> >>
> >> On Wed, 29 Jun 2005 Sct599 at aol.com wrote:
> >>
> >> >  Hello Group:
> >> >
> >> > I am looking for any input you all may be  able to provide concerning a
> >> > failure with my T-238 (original  model).
> >> >
> >> > Found that the U5 voltage regulator had failed  putting approx 11 volts 
> >> > on
> >> > the 5 volt buss. Replaced U5 and no  indication of unit coming back to
> >> life.
> >> > Performed the "Power up  and initial testing" procedure and all appears 
> >> > to
> >> be OK.
> >> > Is it  safe to assume that the U3 microprocessor and possibly all
> >> components
> >> > powered by the 5 volt buss have been destroyed?  If so, is there  any 
> >> > hope
> >> in
> >> > repairing this unit?
> >> >
> >> >  73,
> >> > Scott - NØLNE
> >> >  _______________________________________________
> >> > wxsig mailing  list
> >> > wxsig at lists.tapr.org
> >> >  https://lists.tapr.org/cgi-bin/mailman/listinfo/wxsig
> >> >
> >>
> >> --
> >> 73,
> >> John,  W9DDD
> >>
> >>
> >> _______________________________________________
> >> wxsig  mailing  list
> >> wxsig at lists.tapr.org
> >> https://lists.tapr.org/cgi-bin/mailman/listinfo/wxsig
> >>
> >>
> >>
> >>
> >> _______________________________________________
> >> wxsig mailing list
> >> wxsig at lists.tapr.org
> >> https://lists.tapr.org/cgi-bin/mailman/listinfo/wxsig
> >>
> >
> > -- 
> > 73,
> > John, W9DDD
> >
> >
> > _______________________________________________
> > wxsig mailing list
> > wxsig at lists.tapr.org
> > https://lists.tapr.org/cgi-bin/mailman/listinfo/wxsig
> > 
> 
> 
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-- 
73,
John, W9DDD





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