[Elecraft] PA-KX1
Ron D'Eau Claire
[email protected]
Sat Jan 10 19:17:07 2004
Thank you VERY MUCH Gene!=20
Since you didn't put it on the reflector, I'm cc-ing the reflector on =
this
reply as well as John who asked the original question.
I looked at that message reply about six times with a "nagging" feeling =
this
morning, but I was in a hurry to get to the office and never saw it.
Apparently you are the ONLY one who caught it too! That's the value of =
the
reflector. When we trip up, someone sees it!=20
I hope I didn't lead John (or too many others) astray. And you make a =
good
point that it applies to NPN transistors. NPNs are very common because =
they
require a positive voltage with respect to the base on the collector, =
but
there are plenty of PNPs out there. The bias is reversed for them, and =
by
putting the positive ohmmeter lead on the base should show forward bias
diode action (conduction) and putting the negative ohmmeter lead on the =
base
should show no conduction to the base or collector.=20
73,
Ron AC7AC
-----Original Message-----
From: Gene Fuller [mailto:[email protected]]=20
Sent: Saturday, January 10, 2004 3:55 PM
To: Ron D'Eau Claire
Subject: Re: [Elecraft] PA-KX1
Hi Ron,
I believe you will find that an NPN transistor conducts from base to =
emitter
AND base to collector when the base is connected to the positive lead of =
the
ohmmeter. No conduction when the negative lead is connected to the base.
In normal use the collector to base junction is reverse biased, but when
testing out of circuit the base to collector junction can be forward =
biased
just as easily as the base to emitter junction.
I am sure you know this, but it did not come out correctly in your =
response
to Steve.
73,
Gene, W4SZ
*******************************************************************
Hi Steve,
Any "bipolar" transistor like Q6 is essentially two diodes, back to back
with the base the common connection, so you can test it as two diodes as
follows. If you have a diode check function on your DMM, use it. =
Otherwise
use Ohms range.
1 - Put the positive DMM lead on the base and you should find a forward
biased diode (conduction) to the emitter and a reverse-biased diode (no
conduction) to the collector.
2 - Put the negative DMM lead on the base and it's reversed - no =
conduction
(reverse biased) to the emitter and conduction (forward biased) to the
collector.