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[wxsig] Help with T-238 failure

John Koster w9ddd at tapr.org
Wed Jun 29 11:32:17 UTC 2005


I didn't think about the heartbeat.  That alone might narrow things down 
to the processor and the oscillator.  Of course once you get those going, 
there may be other problems. 


I was hoping that Will would chime in here, but I think he is on a trip at 
the moment.  

I have the same problem with the scope.  Not enough BW.  I do have a logic 
probe that helps in most cases.  

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
> 
> 
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> 
> 
> 
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-- 
73,
John, W9DDD





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