Subject:
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U14 problem
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Thu, 14 Nov 1996 23:57:21 GMT
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Original-From:
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Troy N. Stephens <tstephens@&AntiSpam&wesleyan.edu>
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Viewed:
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2209 times
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I'm having a problem at stage 5.1 (memory power supply) of assembling my
(first ever) Handy Board. The main and interface/charger boards have
passed all tests up to this point.
I've just installed C4, C5, and U14 according to the instructions. When
I plug the DC adapter into the Handy Board (interface/charger board is
completely out of the picture), I read about +.02 V where the memory power
supply is supposed to come in, and U14 rapidly gets hot! I read +19.6 V
at pin 3 of U14, and 0 V at pins 1 and 2 of U14. I tried a replacement
for U14 thinking it might have been fried, but nothing changed.
Any idea what might be going on here? I'm kind of surprised to see +19.6V
coming in out of the power supply circuit, though I don't know if I should
be. I thought this was supposed to be more like +12 V. I am using the
Panasonic model KX-A11 DC adapter I received with my kit from Gleason
Research (which is marked DC 12V 500 mA). The voltage measured at the DC
adapter output itself is 19.9 V ! I have checked the board for obvious
things like solder bridges or poor connections, but there are no such
defects that I can see. I have the Handy Board schematics here as well as
the assembly instructions, by the way.
Any help in diagnosing this problem would be greatly appreciated!
Thanks!!!
-Troy
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Message has 1 Reply:
 | | Re: U14 problem
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| Firstly, 19.9v is a normal unloaded voltage from a 12v DC adapter. The reason: these common wall adapters are unregulated, and voltage output varies inversely to current. I.e., if there is no load, the voltage is higher than the rated voltage; if (...) (29 years ago, 15-Nov-96, to lugnet.robotics.handyboard)
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