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OPERATING INSTRUCTIONS FOR THE "UNIVERSITY"
MODEL TVT VALVE TESTER AND THE TST/2 VALVE
AND CIRCUIT TESTER.
GENERAL
This instrument has been developed to fulfil the requirement
of a completely flexible method of testing modern radio and
television valves. It incorporates lever switches for element
selection, which enables it to test any future types of valves
regardless of their base connections.
A masking plate covers three spare socket holes in the front
panel to enable additional sockets to be fitted should new types
come into use.
The principle of testing conforms to standard RMA practice
CONTROLS
"LINE" This control is situated in the bottom left hand
corner of the front panel and its purpose is to compensate for
varying line voltages.
FILAMENT VOLTS "A" Filament volts are selected for the valve
under test by two switches, which are situated next to the "LINE"
switch on the bottom of the front panel. The filament voltages
available are from 0.6 to 117, the first switch selecting up to
12.6 volts and second switch the higher voltages.
To obtain filament voltages above 12.6 it is necessary to
turn the first filament switch to "HIGH VOLTS", then the second
switch is set to the voltage required. Until the first is in the
"HIGH VOLTS" position the second switch is inoperative.
ELEMENT SELECTOR "B-C-D" The element selector takes the form
of ten lever switches, numbered from 1 to 10. Each of the
switches from 1 to 9 represents the pins of a valve, the number
above each switch from 1 to 9, corresponding to the pin numbers of
the valve, according to standard valve numbering practice, and
switch 10 represents the "TOP CAP".
This form of switching enables the tester to switch any valve
connection to any test position, or in the case of a valve having
an internal connection or tapped heater to completely isolate a
valve pin.
The letters "B", "C" & "D" refer to the test positions to
which valve elements may be switched. These test positions are
given in the valve testing tables.
When the lever switches are in the "NORMAL" position they are
connected together to one side of the heater voltage. Normally
all elements are left in this position with the exception of the
element nearest the cathode and one heater connection.
Position "B" is the heater connection and one heater pin is
switched to this position.
Position "C" is an open circuit position and any valve pin
which has an internal connection which may tend to interfere with
testing is switched into this position.
Position "D" This is the "TEST" position. The element which
is nearest to the cathode inside the valve is switched into this
position and the tester applies a voltage to it for emission
testing. Results are indicated directly on a three coloured scale
marked good, questionable and bad.
TEST SELECTOR "E" This switch is situated fourth from the
left on the bottom of the front panel, and its purpose is to selet
the test function required.
When switched to "LINE", the meter indicates line voltage,
and the "LINE" switch should be set to a position to make the
meter pointer reach the arrow at full scale deflection.
This test should be carried out with the valve under test in
position.
In the "SHORTS" position the instrument will indicate shorts
between any elements in the valve under test. To enable selection
of shorts which may only occur when the cathode is heated, after
applying filament voltage to the appropriate pin, the heater will
warm up and each remaining lever switch in turn may be moved to
the "TEST" position. The neon lamp will then indicate any
continuous path between elements in a tube. When the levers
corresponding to the second or other filament connections are
operated, the lamp should light, indicating filament continuity.
So this will not be mistaken for a short circuit, the levers
corresponding to other filament connections are indicated at the
left hand side of the column marked "SHORTS INDICATION" in the
data sheets. Some modern tubes have one or more internal
connections linking certain base pins. In order that these may be
distinguished from actual short circuits, the number of any levers
which should produce a glow in the neon lamp are also listed in
the "shorts indication" column. Should the lamp glow when levers
other than those listed in this column are moved to the "TEST
POSITION" a short circuit exists in the valve and no attempt
should be made to apply and emission test.
The position "1","2" and "3" of switch "E" are the test
positions for emission, and in general position "1" tests diode
plates and small battery valves with limited emission and TV
picture tubes. Position "2" tests all general purpose R.F.
pentodes, tetrodes, triodes etc., and position "3" all power
valves and power rectifiers.
RANGE "F" The range potentiometer is situated in the bottom
right hand corner of the front panel and its function is to
correctly adjust the meter sensitivity. So that average new
valves cause the pointer to register near the right hand end of
the "GREEN" portion of the meter scale, valves which are better
than average may cause the needle to read full scale deflection or
move slightly beyond the green segment.
TOP CAP The top cap lead supplied with the instrument is
plugged into socket marked "TOP CAP" and is connected to those
valves fitted with caps, prior to testing.
TESTING PROCEDURE
1) See that all lever switches are in the "NORMAL" positions.
2) FILAMENT VOLTS Switch "A" to correct voltage as shown in
column "A" of valve tables.
NOTE: For voltages exceeding 12.6, the left hand "A" switch
must be turned to "HIGH VOLTS".
3) Determine from "B" column in valve tables the pin number for
one of the filament connection and move correspondingly numbered
lever switch to "B" filament position.
4) Plug valve to be tested into appropriate socket.
5) Set "E" switch to "LINE" and adjust "LINE" switch to set meter
pointer to arrow at full scale deflection.
6) Set "E" switch to "SHORTS" and test for shorts by setting each
lever switch in turn to "D" "TEST" position, returning each switch
to "NORMAL" after observing whether or not the lamp lights. It is
not necessary to move the lever already in the "B" "FILAMENT"
position
The lamp will normally glow when a lever corresponding to the
second end of the filament or a filament tap is brought to the
"TEST" position. To distinguish the normal glow indicating the
filament continuity from a short circuit, base pins corresponding
to filament connections which should produce a glow are listed on
the left hand side of shorts indication of the chart.
7) Refer to column "D" of valve tables and throw corresponding
lever to "D" "TEST" position.
8) Set control "E" to position "1", "2" or "3" as indicated in
"E" column in valve table.
9) Advance control "F" to number indicated in "F" column and
observe condition of valve on meter scale.
10) Remove valve and return controls to "NORMAL" or off.
NOTE: To avoid any chance of danger to meter it is important
that valve is removed before the lever switched to "B Filament" is
returned to "NORMAL".
In the case of centre tapped heaters the lever corresponding
to the centre tap should be used and voltage should be that
applicable to parallel operation of the heater valves.
TESTING NEW TYPE VALVES (not shown on chart)
1) Set FILAMENT VOLTS to correct position for valve as determined
from published data books.
2) Select one heater pin and switch lever switch corresponding to
this pin to "B FILL" position.
In the case of centre tapped heaters the lever corresponding
to the centre tap should be used and the voltage should be that
applicable to parallel operation of the heater halves.
3) Plug in valve and adjust "LINE" switch.
4) Set "E" switch to shorts and carry out shorts test in the
normal manner by setting each lever switch in turn to "D TEST"
position.
Base connections in a valve data book will reveal any
internal connections which should produce an indication.
5) The emission can be tested by determining from a valve data
book the lever switch with the number corresponding to the element
closest to the tubes filament or cathode.
In all ordinary types of tubes this will be the control grid.
In frequency changers it will be the oscillator grid and in diodes
and rectifiers, it will be the diode plates.
6) Switch "E" should be set to position 1 for diodes, to position
2 for all battery tubes and for ordinary A.C. operated amplifying
tubes, and to position 3 for A.C. operated power output tubes and
rectifiers.
7) Slowly advance "F RANGE" control to a position to give a
"GOOD" valve reading on the meter scale. This setting should be
obtained with a valve know to be good and recorded for future use.
8) Remove valve, then return all switches to "NORMAL".
NOTE.
Television picture tubes and EHT rectifiers may be tested in
the model TVT or TST/2 for filament continuity, internal short
circuits and electron emission from the cathode, like sny other
tube. This will show up the majority of faults which develop in
these types of tubes.
The presence of any appreciable amount of air or gas within
the envelope will be indicated by a low emission reading.
It is possible with these tubes however, that slight traces
of gas may not reduce the emission reading but yet may ionise
under the stress of the high voltage of the order of 14,000 to
18,000 volts present in a television receiver.
If an EHT rectifier or picture tube shows a defect when
tested then the tube is definitely faulty. If it gives a "good"
indication, it is wise to check in a television receiver in case
of gas content.
E.H.T. Rectifiers.
E.H.T. Rectifiers are designed to pass very low pate current
only usually about 0.5 ma so that even a good tube will only cause
the needle to move between 25% and 40% of the way across the scale
with the range control "F" set to 100. It is important to set
switches A, B and C before inserting tube in socket.
PICTURE TUBES.
The TVT Picture tube adapter is intended for use with the
Model TST/2 and the Model TVT valve tester and it is to be used in
accordance with the operating instructions for these instruments.
This adapter, when used with the TST/2 and the T.V.T. will
test all duo-decal based picture tubes for heater continuity,
emission and short circuited elements.
The TST/2 and the TVT do not illuminate the screen of a picture
tube under test.
TST/2 MULTIMETER SECTION.
The Multimeter facilities of this instrument have a wide
range of applications. It will measure voltage, current and
resistance values accurately, and the design incorporates an
efficient output meter. Following is a description of how the
various sections are used. There are further and wider
applications for this instrument which will manifest themselves as
the operator becomes more familiar with the Multimeter.
Unless the operator understands the voltage and current
readings of various circuits, it is advisable to always use the
highest range available to obtain an approximate reading, and then
choose a lower range which will be more suitable for an accurate
reading. This will prevent damage to the meter from excessive
overload.
D.C. VOLTAGES
Turn the central selector switch to the desired voltage range
and make sure that the right-hand switch is turned to that
position marked "D.C." The negative, or black, test lead is
inserted in the negative jack on the instrument, and the red test
lead is inserted in the positive jack. The two test, prods are
then touched to the necessary parts of the apparatus under test,
and the meter will read the difference in potential between the
two points touched, which is actually the voltage. It is
necessary to remember that voltage is the difference in potential
between any two points.
If it is desired to measure the voltage on the elements of a
valve, the metal chassis of a radio receiver or amplifier is
usually regarded as forming the negative side of the circuit. For
instance, if it is desired to measure the plate voltage of a
valve, the appropriate range would be selected, the positive test
lead placed on the plate contact of the valve, and the negative
test lead placed on the chassis, The meter would then read the
valve's plate voltage. This method does not apply to the
measurement of negative grid bias.
To measure the negative grid bias, the negative test prod is
placed on the grid and the positive test prod is placed on the
negative filament or cathode contact. The negative bias will then
be indicated on the meter. This method will be inaccurate if a
high value of resistance is included in the grid circuit, such as
a resistance capacity coupled stage. In this case, the negative
test prod should be placed on the end of the grid leak resistor,
which does not connect to the grid.
When making voltage measurements, it is not necessary to
remove or disconnect any wires.
A.C.VOLTAGES
To measure alternating voltage, the only rearrangement of the
controls on the instrument is to turn the right-hand switch to
that position marked "A.C." The appropriate voltage range is then
selected in the ordinary way on the range selector switch, and the
test prods, when plugged into the instrument, can then be
connected to the two points between which it is desired to measure
the voltage difference. Since alternating voltage has no fixed
negative or positive potential, the negative or positive test lead
from the instrument can be placed on either of the two points
which are under test. However, to form a safety habit, it is
always wise to place the negative lead on the low potential side
of the circuit or that side of the A.C. voltage which is connected
to earth. If this is inconvenient, the operator need not worry
any further.
When measuring alternating voltages on the 10-volt range, the
lowest meter scale, marked "10 V. A.C. only" should be used. When
using 50,250 and 1,000 V. ranges, measurements should be made on
the upper set of voltage graduations.
D.C. CURRENTS
In making current measurements, it is necessary to break the
circuit and insert the test leads so that the meter is placed in
series with the circuit. For instance, to measure the plate
current of a tube, the wire on the plate contact would be removed
and connected to the positive side of the meter. The negative
meter lead would be connected to the plate contact and the
selector switch would be turned to the desired range, and then the
set switched on. The plate current of the valve would be
registered on the meter. This procedure also applies to any other
circuit in which it is desired to measure current in milliamperes.
The circuit is simply broken and the meter inserted in the break
to complete the circuit again.
Where the current value is unknown, it is always wise to
commence on the highest range, and then turn the selector switch
down to that range which give the most convenient deflection of
the needle on the meter.
A.C. CURRENTS
The TST/2 by itself is only intended to measure alternating
(A.C.) current on the 1mA range, in which case the upper voltage
graduations are used. This range can be extended by using the
MRCT "University" current transformer which is available as an
extra. The MRCT needs no soldered connections it simply connects
by terminals to the TST/2 and a switch on the MRCT selects the
desired A.C. current range. It extends the TST/2 to read the
following A.C. current:-
2.5, 5, 10, 25, 50, 100, 250 and 500mA A.C. and 1, 2.5, 5 and 10
amperes A.C.
RESISTANCE
This instrument will measure values of resistance in four
convenient ranges:- 0-1,00 ohms, 0-10,00 ohms, 0-100,000 ohms and
0-10 megohms.
To measure values of resistance below 1,000 ohms, the selector
switch is turned to the position marked "R X 1." The test leads
are inserted in the instrument and then the test prods are
touched together so that the meter needle will swing right over to
the position marked "O" on the upper meter scale. If it does not
exactly reach the "O" mark on the ohms compensator at the left
hand side of the instrument is turned until the needle indicates
zero resistance. The meter is then ready for use.
To measure resistance one side or both of the resistance or
other part should be disconnected from the rest of the circuit and
the test prods placed on its terminals. The value of resistance
will be shown on the ohms range.
For values up to 10,000 ohms the switch is turned to the
position marked "R x 10" and the scale figures must be multiplied
by 10 to give the correct resistance. For example if you are
measuring a resistance of 4,000 ohms and the switches are turned
to the correct position then the meter needle will indicate 400.
Multiplying this by 10 gives 4,000 which is the correct reading
assuming that the resistor is in good order.
When measuring in the range of 10,000 ohms, it is necessary
that the prods are touched together again and the needle adjusted
for zero resistance by use of the ohms compensator.
For values up to 100,000 ohms the range switch is turned to
the position marked "R x 100" and the procedure is carried out as
explained previously. For measurements up to 10 megohms turn
switch to "R x 10,000" and proceed as before. When using the "R x
10,000" range the instrument must be connected to power mains.
In measuring resistance it is necessary that the right hand
switch be turned to the position marked "D.C." Always before
measuring resistance make certain that the test prods are touched
together and the ohms compensator adjusted so the meter reads zero
before operation. The purpose of this ohms compensator is to
compensate for any variation in battery-voltage which will enable
you to obtain a maximum life from the built in battery.
CAUTION - Before attempting to measure the resistance of any part
of radio or electrical apparatus, be sure to switch off the power
or to disconnect one wire from each battery in the case of
battery-operated equipment.
OUTPUT METER
In addition to measuring ordinary A.C. voltages over a wide
range the Multi-meter can also be used as an output meter the
right hand knob on the instrument is turned to the position marked
"OP" and the range selector is turned to an appropriate voltage
and "DB" range. The test leads are inserted in the instrument,
and one lead is attached to the chassis while the other lead is
touched to the plate of the output or power valve in the receiver
or amplifier under test.
Small push-on clips are provided with the instrument. These
easily and conveniently fit on the test leads, so that it will not
be necessary for the operator to hold these on to the point under
check in the chassis. They can be clipped on to any convenient
wire or terminal leaving the operator's hands free for alignment
of the set.
If the range selector is turned to 10 volts when using this
as an output meter, it will give a very sensitive reading,
However, it will be found necessary for the volume of the receiver
to be kept low, so as not to damage the meter. This 10-volt range
is recommended for aligning sets. If the output meter is required
for a purpose other than alignment, the 50-volt or 250-volt will
be found quite suitable.
Used in this manner, the instrument will facilitate the
alignment of a receiver, especially when a modulated oscillator or
signal generator is used as the source of signal.
The meter scale is also calibrated in db. When using db
ranges, the figure indicated by the Selector Switch must be added
to that indicated by the meter pointer.
BATTERY REPLACEMENT
The resistance measurement section of this instrument
utilises a standard 1.5-volt 950 dry battery cell, for the
ranges R, R X 10 and R X 100. This usually lasts up to twelve
months without replacement. It will be known when the battery is
due for replacement by the fact that the ohms compensator on the
panel will not enable the pointer of the meter to be brought right
to the zero mark. The R X 10,000 range is powered by rectified
A.C. furnished from the valve testing section.
GENERAL
The primary purpose of this instrument is to measure D.C.
voltage, currents and resistances, as well as A.C. voltages and
output voltages. The instrument is accurate and is easily
portable.
It will cover nearly all of the routine checking required in
a radio receiver, and in general radio equipment. It must be
remembered that voltage measurements is a receiver will not only
indicate that there is voltage available, but if they are measured
through any of the components in the receiver, they will indicate
whether that component is open circuit or otherwise by the
indication of voltage on the meter. Faulty and intermittent
transformers can be tested by using the ohms section of the
instrument, and continuity test al all components can be made with
this section. The instrument will also indicate short circuits
and open circuits, leaky condensers, faulty resistance, broken
connections and incorrect values. The output meter section can be
used to indicate a standard of output from apparatus under test,
and constant use of the instrument will bring many new suggestions
to mind.
The meter needle should normally coincide exactly with the
zero end of the voltage and milliamp scales when the meter is not
in use. Should it not do so, it can be adjusted to zero by means
of the large bakelite screw on the face of the meter, just below
the glass.