In article <20001204023447.5467.qmail@web1608.mail.yahoo.com>, James C.
Owen, III <k4cgy_list@yahoo.com> writes
>If Pin 19 is at zero volts when it should be 5V then there are
>only two possibilities. 1) the pull-up resistor R14 is bad or the
>5V to the hot side of R14 is going away. 2)there is an internal
>failure in the chip U10 that takes that pin to ground.
>I'm betting on a bad R14 or maybe a bad solder joint.
Hi Jim
As you say, I ought check for bad soldered joints around the pull-up
resistor, and check the resistor itself, but that wouldn't explain why
the keyer will sometimes not send dashes even when pin 19 (dash pin)
*is* being grounded (measured at the pin) by the paddle connection.
>Chips can and are intermittent. This assumes that the failure is
>not a complete junction failure. There are quite a few wire
>bonding failures that crop up from time to time. Thermal cycles
>cause stress on the wire bonds and if not enough slack was left
>can cause a bond to break.
I take your point. I've not had the opportunity to look at chips under
a microscope such as yours, but can imagine how fascinating (and
informative) it must be.
>I will be glad to to inspect it under
>my Zeiss microscope and take pictures of said failure, if found.
>Oh! you're in "G" land, guess shipping it not a good idea.
If I do end up replacing the chip, I could be tempted to post it to you
(hang the expense, Hi) for closer inspection - not sure if I could
relieve it of its top though!
Thanks again Jim ..
--
72, peter g3xjs
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