Dear Jestine,

Please I have a small problem and I need some advice.
I have a faulty TV with a faulty power supply. When I checked one of the output 3 legs IC1431T ,with coponent
analyser it gave the folowing result,
NPN DARLINGTON TRANSISTOR
COLL EMIT
DIODE PROTECTION BETWEEN C-E
RESISTOR SHUNT BETWEEN B-E HFE NOT ACCURATE DUE TO  TO B-E RES
CURRENT GAIN .
HFC=1452
TEST CURRENT
IC=2.50Ma
BASE-EMITTER V
VBE=1.54V
TEST CURRENT
IB=3.78MA
LEAGAGE CURRENT
Ic=0.00mA

Because the tester indicated HFC is not accurate,I decided to buy one. I was given IC FAN431 as the same as mine. When I tested it with my component analyser it did not give any readings.
The only information that came on the screen is NPN Transistor.

When I went to the shop to complain, they told me the semi conductor tester can not test that IC and that what they have given me is the same as mine and that the results I obtained were false and nothing and not to be relied on.

Please are they telling me the truth that my component analyser Peak Atlas DCA model DCA55 CANNOT actually test this
IC AN1431T SEMICONDUCTOR.
Please is this IC FAN431(from shop) = IC1431T(mine).

Yours sincerely,
A.

Reply:

Hi A,

It is actually a TL431 IC (Adjustable Output Shunt Regulator) located at the secondary side of power supply near optoisolator IC. Since this is an IC thus you can’t test it with any meter for accurate reading. The best way to find out if it is good or bad is to direct replace and retest. Remember, it can come in many different front version such as S431, A431 and etc. If you want more info do visit this link:

http://www.jestineyong.com/how-to-test-adjustable-precision-shunt-regulator-tl431/

Jestine

About

Jestine Yong works as an Electronics Repair Lecturer in Kuala Lumpur Malaysia and his training website is http://www.NoahtechElectronicsTraining.com. You can check out his repair blog at http://www.JestineYong.com