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formed. Finally, a selected potential is applied to the tetrode connection to produce a potential
difference between tetrode connection and base. Proper tetrode action is indicated
if
the applied
potential decreases the gain reading.
Transistors Are Temperature - Sensitive
MOST lebo LIMITS LISTED ON THE DATA SHEETS SUPPLIED WITH YOUR T-65 ARE
BASED ON AN AMBIENT TEMPERATURE OF 77
0
F. (25
0
c.).
ICbo CAN DOUBLE FOR EACH
18
0
F. INCREASE IN TEMPERATURE OR MAY READ APPROXIMATELY HALF ITS VALUE
FOR EACH 18
0
F. REDUCTION IN TEMPERATURE. IF THE FIRST lebo READING IS QUITE
LOW, THE OPERATOR NEED NOT BE PARTICULARLY CONCERNED ABOUT ROOM TEM
PERATURE. HOWEVER, WHEN READINGS CLOSE TO THE REJECT POINT ARE OBTAINED,
THE OPERATOR SHOULD CHECK ROOM TEMPERATURE BEFORE MAKING A FINAL JUDGE
Ml;NT OF lebo. DO NOT HOLD THE TRANSISTOR IN THE FINGER TIPS WHILE TESTING
lebo, SINCE HEAT FROM THE FINGERS MAY AFFECT THE lebo READING.
. Transistors are classified as PNP or NPN. The only difference between these two classes,
so far as testing the transistor is concerned, is the polarity of the applied test voltage and
metering circuit.
In
other words, all tests performed on a PNP transistor are the same as on
an NPN transistor, except the Function Selector switch of Model T-65 applies test voltages of
the correct polarity to the transistor.
A negative potential is applied to the collector of a PNP transistor, whereas a positive
potential is applied to the collector of an NPN transistor.
OPERATING INSTRUCTIONS
Transistors
AGAIN, ONE OF THE MORE IMPORTANT FACTORS TO REMEMBER WHEN TESTING
TRANSISTORS IS THEIR SENSITNITY TO TEMPERATURE CHANGES. TRANSISTORS SHQULD
NOT BEHELD IN THE HAND DURING TESTS,SINCE THIS CONTACT IS ENOUGH TOCHANGE
THE TRANSISTOR OPERA TION.
Check the zero setting of the meter needle before turning on the instrument.
If
necessary,
zero the needle by means of the adjustment screw on the front of the meter.
1. Set Switches "A", "B", and
"c"
to the settings indicated in the Test Data sheets.
2. Determine whether the transistor is "NPN" or "PNP" from the data sheets and set the
lower right hand (Function Selector) switch to the corresponding "SHORT" position. Move power
switch to "ON" and set "ADJUST LINE" control so meter pointer lines up with "ADJUST LINE"
calibration mark.
3. Identify the transistor leads by referring to the illustrations of different transistor
types and insert the leads into the panel socket. Make sure the proper numbered lead terminals
insert into the correspondingly numbered parts of the socket, and the uninsulated transistor
leads are not shorting to each other.
NOTE:
If
the transistor cannot be accomodated by either of the two sockets, use the alli
gator leads to connect to the transistor, carefully observing the numbering identi
fication on both the transistor and alligator leads. See illustrations accompanying
data.
If
the transistor is a power type with the collector terminating in the metal
transistor case, use the black alligator lead to clip to the transistor shell.
4. Press the "READ METER" button and read the 0-100 meter scale. Compare this
reading with the reading on the data sheet.
If
the reading is higher on the scale than on the data
sheet, reject the transistor as shorted. No further test should be performed if the transistor
does not pass this test, since a shorted transistor can cause excessive meter current to flow
in subsequent tests.
Page 32
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