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[wxsig] Crashing and random characters

Mark Patton k0yg at msn.com
Mon Jun 30 14:42:30 UTC 2008

I replaced mine with a 3-terminal switching regulator made by TI.  I got 
it from Digi-Key.  I think the one I used was 78SR105HC-ND.  It 
physically is much larger but pin compatible.  I used epoxy and mounted 
it to the back of the main PB board.  I just fit (insulate it first 
though...).  It's been working perfectly for the past 2.5 years.  I'm 
sure there are others that would work just as well.


Ken Brown wrote:
> A couple of years ago someone posted a message about this subject and
> he said he replaced the voltage regulators with drop in replacement
> TI switching regulators.  I have done the same thing and my original
> T-238s are now quite stable.  They are three terminal drop in
> replacements for the 7805 regulators. They cost about $10 at the time.
> Unfortunately I don't have the part number at hand here but could look
> it up this evening.  I got them from Mouser.
> Ken
> Guy Story KC5GOI wrote:
>> William Beals wrote:
>>> Guy:
>>> Ouch, that doesn't sound good.  It also doesn't sound familiar
>>> unfortunately.
>>> You definitely want the 1.15.8 firmware, it is a lot better and more stable
>>> than 1.15.4.
>>> Any chance the voltage regulator is overheating?  It can happen reliably if
>>> your incoming supply is much over 12V and your backlight is on.  For a
>>> lightly loaded and unregulated wall wart, that voltage can easily get up to
>>> 14 or more volts.  The regulator handles it for a while, but then starts
>>> going into thermal shutdown which isn't a graceful on/off shutdown.
>>> will
>> Will, the heat sink for the voltage regulator is getting too hot to 
>> touch.  I do not require the back light.  I will check the schematic 
>> tonight for the trace the backlight is on and cut the trace.  I remember 
>> we had to do that on the original kit year ago due to a short on that 
>> trace.  The power supply is putting about 13.3, and I am running 4 
>> instruments.
>> Thanks.
>> Guy
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