RECORDER,
SOUND RANGING, No.1,
MARK II
CONTENTS
CHAPTER 1
Description-
PAGE
General .. .. ..
.. .. .. .. .. .. 3
Galvanometer .. .. ..
.. .. .. .. .. 4
Time motor .. ..
.. .. .. .. .. .. 4
Lantern .. .. ..
.. .. .. .. .. .. 4
Relay .. ..
.. .. .. .. .. .. .. 4
Driving motor .. .. ..
.. .. .. .. .. 5
Gearbox .. .. ..
.. .. .. .. .. .. 5
Switches .. .. ..
.. .. .. .. .. .. 5
Stand .. ..
.. .. .. .. .. .. .. 5
Tuning fork .. ..
.. .. .. .. .. .. 5
Test panel .. .. .. ..
.. .. .. .. .. 5
Camera and automatic developer .. ..
.. .. 6
Solutions-developing and fixing .. .. ..
.. 8
Transformer unit .. .. .. ..
.. .. .. .. 3
Camera drive and knife operating mechanism .. .. 9
CHAPTER II
To instal the recorder .. .. .. .. .. . .. .. 10
Test for galvanometer string sensitivity .. .. 11
Adjustment of optical system .. .. .. .. .. .. 12
LIST OF PLATES
Recorder, S.R., No. 1, Mark II-
PLATE
Side view of base assembly ..
.. .. .. .. .. .. I
Front view of base assembly
.. .. .. .. II
Showing pqsition of tuning fork and amplifier ..
III
View of complete recorder
.. .. .. .. .. .. IV
Tuning fork and amplifier .. .. .. .
.. .. .. V
Front view of test panel
.. .. .. ..
.. VI
Rear view of test panel
.. .. .. .. .. VII
Camera and automatic developer
.. .. .. VIII
Transformer unit
.. .. .. .. .. IX
Galvanometer and components
.. ..
.. X
Galvanometer assembly
.. .. .. ..
.. XI
Harp assembly ..
.. .. .. .. .. XII
Time motor and lantern
.. .. .. .
.. XIII
Camera driving mechanism
.. ..
.. .. XIV
Instrument base on travelling base
.. .. .. XV
Automatic developer on travelling base
.. .. XVI
Transformer unit in travelling case
.. .. XVII
Box containing spare parts
.. .. ..
XVIII
Wiring diagrams-
Recorder, S.R., No. I, Mark II
.. .. .. XIX
Three-valve amplifier, tuning fork and time motor .. XX
Testpanel
.. .. .. .. .. ..XXI
Transformer
.. .. .. .. ... XXII
CHAPTER I
SOUND RANGING RECORDER
DESCRIPTION
Note -Should it be desired to refer to the theory of sound-
recorders or to the Recorder, SR., No. 1, Mark I,
such information can be obtained from Section 34 of this
handbook.
The Mark II recorder has the general Capacity of the Mark I,
but has been assembled in a more compact form.
The galvanometer, time motor and lantern, three-point
relay, driving motor and gear-box, together with the necessary
Switches and brackets for securing the automatic developer in
position, have been mounted on an aluminium alloy base and
constitute one complete unit. This is mounted on a tubular
steel stand and locked in position by four screwed pins, thus
making the base effectively a part of the stand.
The stand is a tubular steel frame with a shelf on which the
transformer unit and batteries are housed. A cabinet mounted
in the frame carries the tuning fork, amplifier, H.T. battery
and a panel on which are mounted the galvanometer string
testing gear and shunts. Levelling of the recorder is provided
for by means of levelling screws attached to three of the four
feet of the stand.
The camera is mounted as part of the automatic developer
unit and the paper speeds of both are the same, i.e. the record
is developed at the speed with which it is delivered from the
camera.
This arrangement has necessitated the provision of an
automatic cutter for the record, the mechanism being actuated
by the driving motor, immediately the advanced post releases
its sending key, in order that developing may continue unchecked.
The whole of the camera and developer case is secured to
the side of the instrument base by special brackets and clamps,
which ensure correct registration with the gear-box coupling.
The large prism reflects the images of the galvanometer
strings and time wheel vanes, throggh a right angle, into the
camera lens. Electrical connections between the units are
made through multi-core shielded cables, plugs and sockets.
The recorder occupies a floor space of 32 in. x 22 in., the
height being 4 ft. 2 in., whilst the weight is approximately
2 1/2 cwt.
A brief description of the principle components, or a com-
parison with the Mark I recorder now follows.
Galvanometer (Plate I)
The galvanometer (1) is a six string
"Einthoven type.,
The field is produced by a permanent magnet of "Alnico"
and has a flux density in a gap of P5 mm., of 16,000 lines
per sq. cm. The harp is a gunmetal casting and harp strings of
20µ copper wire are provided soldered to flat springs, so that
no soldering of strings is required in service use. These,
springs are secured by screws between spring-loaded clamps and
a sensitive adjustment of the string can be effected with a small screwdriver.
The interval between the harp strings has been reduced
to 0·67 mm. so that it has been possible to increase the optical magnification of the
system compared with the Mark I, by
about 50 per cent. without increasing the general dimensions.
The field is inclined at ten degrees to the plane of the
strings, which is normal to the optical axis, thus ensuring that
the strings do not touch one another when deflected beyond The
0.67 mm. interval.
Connection to the strings is made through a seven-point knife switch.
Time motor (Plate I)
The time motor (7) has the essential parts of that used with
the Mark I recorder, but the counter mechanism and prism
holders have been modified.
Two prisms, mounted above two separate counter
mechanisms, are provided so that change over from one speed
to another only involves lifting the motor from its case, turning
it through 180 degrees, and replacing it in the case.
The construction of the prism holders has been simplified.
Each holder is secured in position by a strong flat spring,
against three adjusting screws in the floor of the top motor
casting. Access to the prism adjustment is obtained by
removing the two dust plates on the top cover df the motor
casting.
Connections to the grid and anode windings of the motor
are made through twin plugs numbered 1 and 2, 3 and 4, so
that no confusion is possible as to where they connect.
Lantern (Plate 1)
The lantern (6) is in every respect similar to that of the
Mark I recorder and no further description is required.
Relay (Plate 1)
The relay (4) comprises two electro-magnets one of which
closes the lamp and camera clutch circuits and the other the
motor circuit. These are wired into the main circuit in such
a manner that the advanced post has complete control of the
lamp and camera clutch, but can only close the motor circuit.
The motor will continue to run until the operator breaks
the circuit, by means of a switch mounted in front of the inst-
rument base. This switch can also be used for local control of
the recorder.
Driving motor (Plate I)
The driving motor (3) is a 12-volt D.C. shunt wound motor
and is coupled directly to the gear-box through a Renold's
coupling.
Gear-box (Plate I)
The gear-box (2) is essentially the type used with the
Mark-I recorder except that the gear ratios have been modified
to give a lower speed at High speed and a higher speed at Low
speed, than the Mark I type, i.e. 16 cm. per second and 4 cm.
per second, as against 20 cm. per second and 4 cm. per second
of the Mark I. The coupling to the automatic developer is
effected through an Oldham's coupling.
Switches
Two switches mounted on the front of the instrument base
(5) (Plate I) allow for test operation of the relay and
lamp.
The power battery is connected through a plug and socket
mounted on the base.
Two brackets are mounted at the side of the base to provide
a fixing, to which the camera and automatic developer unit is
secured in position by means of screw clamps.
Stand (Plate III)
The stand is a tubular steel frame (5) with a low shell (3),
on which the transformer unit (4) and batteries for driving the recorder are placed.
Immediately above this, is a cabinet
which houses the tuning fork and amplifier (2), H.T. battery (1)
and test panel (6). Levelling of the recorder is provided for
by means of levelling screws attached to three of the four feet
of the stand.
Tuning fork (Plate V)
The tuning fork (202.56 cycle/seconds) and method of
mounting are clearly shown in this plate. The driving valve
and output amplifier are mounted alongside The fork on a
Plymax base, so that all parts and connections can be examined
and tested. This unit slides into position between two metal
guides fitted on the base of the cabinet and these hold the fork
and amplifier securely in place. The H.T. battery is housed
on a shelf in the cabinet immediately above the fork.
Test panel (Plates VI and VII)
The test panel carries the galvanometer string test equip-
ment, Test currents provided for are 0.2, 0.5 and 1 m/a.
Six galvanometer shunts are also mounted on this panel.
They are designed to cut down the E.M.F. applied to the
strings in steps of 1/8 and to maintain the impedance of the
transformer secondary circuits, and the string circuits, constant throughout the changes.
By this means, damping and uniformity
of response are also maintained constant.
The six-point relay which connects the transformer
secondaries to the galvanometer is mounted on this panel
and connection between the relay, and the transformer unit,
and between the panel and the galvanometer, are made
through multi-core shielded cable and ten-point plugs and
sockets.
The L.T. supply for the tuning-fork drive and amplifier is
plugged into the panel, and the time motor control is connected
through a five-core shielded cable and five-point plugs and
sockets.
Camera and automatic developer (Plate VIII)
The camera is mounted as part of the automatic developer.
The bromide paper strip roll is mounted on a metal drum with
flanges to keep the paper in position (15). Paper from the roll
passes over a guide roller through a light-tight slit, over another
guide roller, and through a frame closed by a hinged gate which
retains the paper at its true focal distance from the camera lens.
Below the frame, the paper passes between two rollers, both
of which are accurately ground to the same diameter and are
driven Through similar gears from a common drive. The shaft
carrying the gear for the forward roller drive is extended
through the outer case and is coupled to the gear-box through
an Oldham's coupling.
From The paper drive the paper passes between two balanced
guide plates (see Plate XIV) which guide the paper
into the
automatic developer through the knife.
The knife is in the form of a slotted plate and slides between guides fitted
on the underside of the casting carrying the paper mechanism. It is connected through a
lever to a bar which is
supported above the main drive by a spring control. This bar
carries a pawl and the soft iron armature of an electric magnet.
When This knife magnet is energized, the armature is pulled down;
the pawl engages with a ratchet wheel fitted to the main drive
and the bar is forced forward, thus drawing the knife
across the paper slit.
The knife can be operated also by hand through a lever (3).
This mechanism is explained in detail later.
Developing takes place on one band only and this band (2)
runs entirely inside the developer tray (12).
The developer tray (12) is clamped by two screws (7) and
(13) to The back of the case, in guides (6), so that the effective developing length of
the band can be varied continuously.
from high to low speed requirements, while maintaining band
tension and developer level constant. Tension on the developer
band is adjusted by a knurled screw (14). and the tension
should be such that when the paper knife operates, the pressure
between paper and roller (1) is just insufficient to allow paper
to drag on the knife blade.
Developing solution is squeezed from the record by a
pressure roller (4) and three light ebonite rollers, fixed in a
frame (9), guide the record on to the fixing band which carries
it into the fixing solution.
The fixing bath (10) slides into place between guides fitted
on the inside of the developer case, and is locked in position by
a lip and catch fitted on the outside of the case.
The fixing and developer bands are of the endless type and
made of rubber insertion.
Tension is applied to the fixing band by a knurled screw (8),
which locks or releases a cam controlling the pressure on a
roller carrier. This carrier provides two positions for the
fixing band roller, the upper position for high speed and the
lower position for low speed work.
The entire camera and developer case is held firmly in
position on the side of the instrument base by the special
brackets and clamps already mentioned.
This arrangement has been made possible by the provision
of a large prism (5) which reflects the image of the galvahometer strings and time scale
through a right angle into the camera
lens.
The side of the case can be removed in sections for inspection
and cleaning and the band rollers and guides can also be removed.
On Plate VIII the developer is shown fitted for high-speed
developing. In order to change to low speed, the knurled
head (11) is unscrewed and this allows the roller immediately
above it to be rotated through 180 degrees and locked into its
new position, the belt being placed beneath the roller. The
knurled head (8) is now unscrewed, and the fixing roller is
fitted into the lower position on the carrier. The necessary
tension is applied to the belt, and the cater is locked in place.
The developer tray is now moved into the slow-speed
position by unscrewing knurled heads (7) and (13), and sliding
the tray along the guides until. the output end of the tray is
within 5 in. of the pressure roller (1). The tray is then locked in position and the
developer is ready for work.
The amount of developing solution required for filling the
tray is about one pint, and this should be sufficient for a good
day's work.
The fixing bath requires approximately six pints of fixing
solution. It is not necessary to refill the fixing bath daily.
This solution will last for three or four days work.
Developing Solutions
Slow Speed
20 grammes Sodium Sulphite
20 ,, Metol
)
)- Water, 1 pint.
30 ,, Caustic Potash )
High Speed
30 grammes Sodium Sulphite
30 ,, Metol
)
)- Water, 1 pint.
80 ,, Caustic Potash )
Fixing Solution
250 grammes Hypo )To
every 1,000 c.cm. of
10 ,, Metabisulphite ) water.
If the records are being read in a very bright light or if
they are to be kept for some time, the following solution is recommended.
250 grammes Hypo
)
60 ,, Ammonium Chloride
) To every 1,000 c.cm.
25 ,, Bisulphite of Soda
) of water.
10 ,, Potassium Metabisulphite )
Transformer unit, Mark II (Plate IX)
The transformers are similar to those used in the Mark I
equipment, but the galvanometer and line testing gear have
not been included.
The A.P. relay is a relatively new polarized telephone type
mounted. immediately behind the front panel, and can be
inspected through a small inspection door. The panel of this
unit carries six milliammeters indicating the current in the microphones, and another
indicating the current in the A.P.
relay; also six line-balancing resistances and the main micro-
phone battery switch. The line-balancing resistances allow for variation in line
resistance up to 1,600 ohms, in three steps of
400 ohms and ten steps of 40 ohms. Six four-pin plugs and
six pin sockets, mounted three on either side of the line-
balancing resistance panel, allow for change over from Line to
Radio Link working. A socket mounted on top of the
panel allows for a telephone to be plugged in for direct com-
munication with the A.P.
The line, A.P. and earth terminals are mounted on a panel
at the back of the unit. The microphone battery is connected
to the unit by a plug and socket mounted on the panel also.
The whole of this unit is mounted in a brass angle frame-
work, fitted With screwed covering panels sd that any internal
part or connection can be examined.
Camera drive and knife operating mechanism (Plate XIV)
1 and 2. Geared drive.
3 and 4. Paper drive rollers.
3a. Adjustable spacing screw for movement of roller 3.
3b. ,, tension spring.
5 and 6. Contact screws for knife-operating magnet.
7. Contact, held in position by spring-loaded catch.
8. Spring-loaded catch which releases 7 when knife is
operated.
9. Knife-operating arm-spring-loaded.
9a. Lever hinged to 9 and pivoted at 9b.
10. Pawl.
11. Ratchet wheel attached to main driving gear.
12. Knife-operating magnet armature.
13. ,, ,, ,,
,,
14. Spring-loaded roller for lifting knife-operating arm.
14a. Adjustable stop for knife-operating arm.
15. Knife, spring-loaded.
15a. ,, guides.
15b. Lugs and pins fitting into slots in 9a.
16. Camera clutch magnets.
17. Armature pivoted at 17a.
18. Contact for knife operating magnet.
19 and 20. Balanced paper guide plates.
Roller 3 and 4 are the paper drive rollers, and these are
driven through similar gears 1 and 2, the gear ratio being 1/2.
The shaft of the gear (1) is extended through the camera case
and is coupled to the gear-box drive.
The bearings of the paper drive roller (3) are free to move in horizontal slides and are
connected by a bar to which is attached
an adjustable spacing screw (3a). This screw bears on a bell
crank attached to the armature (17). The diagram shows the
armature pulled down by the magnet (16), and when the
armature (pivoted at 17a) is released, pressure on the roller (3)
is also released and is held from contact with the paper drive
roller (4) by the tension spring (3b). The contact (18) (secured
to, but insulated from,the armature (17)) now makes contact
with the screw (6), and this closes the circuit for the knife- operating magnet (13). This
magnet, being energised, pulls
over the armature (12) attached to the arm (9), and at the same
time the pawl (10) engages with the ratchet wheel (11). This
ratchet wheel, moving in a clockwise direction, forces the arm
forward and the connecting lever (9a) (pivoted at 9b) operates
the knife (15) through lugs and pins which fit into slots in the
ends of the connecting lever.
As the arm (9) moves forward, the spring catch (8) is raised
and contact between 5 and 7 is broken. The armature (12)
is released and the spring-loaded roller (14) lifts the Arm (9)
which returns to its original position.
When the magnet (16) is again energised, a cam attached
to the contact (7) (both of which, cam and contact, are secured
free to rotate anti-clockwise only, to the armature 17) lifts the spring-loaded catch (8)
and is held in position until the above operation is repeated.
CHAPTER II
To Install The Recorder
Place the stand on a firn floor and see that the four screwed
pins at the top corners of the stand are in the correct angular position, i.e. the red
lines engraved on the locking plates are.
in line with the grooves on the plates immediately beneath.
The instrument base can now be removed from its travelling
case and placed on top of the stand. It is then secured in
position by giving the locking plates a quarter of a turn each,
in a cldckwise direction.
The automatic developer can now be lifted into position
by fitting the lugs on the back plate of the developer into the brackets on the instrument
base. The swivel screws are then
placed in the grooves on the brackets and before screwing
tight, care should be exercised to see that the driving coupling
is in register with the gear-box coupling.
The transformer unit is placed on its shelf and the ten-point
plugs are plugged into their respective sockets. These are
clearly shown on Plate III.
The 12-volt battery necessary for driving the set is not
shown in Plate III, but this is usually placed on the lower shelf behind the transformer
unit.
The recorder is now ready for use, and provided that the
set has been handed in transport with reasonable care, no
adjustment should be necessary. All parts that need adjust-
ment, with the exception of galvanometer strings, will have
been tested and locked in position belore delivery and should
be left alone.
To start the time motor, plug the two-point plug into the
socket provided at the bottom right-hand corner of the test
panel, and connect the leads to their respective terminals
on a 2-volt battery. Plug in the H.T. supply and telephones. The
tuning fork will then start to vibrate. Press the switch fitted
on top of the plug of the time motor supply and at the same
time give the rotor a light spin, in the direction indicated by
the arrow engraved on the top plate of the motor. The speed
of the motor then increases and it is possible to distinguish in
the telephone the beats between the tuning fork and motor
supply currents, both of which are heard. When the speed of
the motor, as indicated by its note, has reached the zero beat point with the fork note,
the switch is released and the motor
will continue to run on the fork amplifier supply.
All the counter mechanism and prism holders on the time
motor are adjusted correctly on assembly and providing They
are not interfered with should need no attention,
Before attempting to start the motor, see that the nuumbers
engraved on the plug connectors correspond to the numbers engraved
on the motor case.
Test for galvanometcr string sensitivity
Set the switch on the bottom left-hand corner of the test
panel to the current it is desired to put through the string
(O·2 m/a is sufficient for sensitive string tests), and set the adjacent string selector
switch to No. 1. Switch on the lamp,
operate the "Press for Test switch and note deflection.
Repeat for 2, 3, 4, 5 and 6. Should the sensitivity need
adjusting, slide back the cover on top of the harp until the six adjusting screws
(enclosed by metal tubes) are accessible. The necessary adjustment is then carried out
with a small
screwdriver.
To replace a string, push the small lever which operates the
knife switch on the top right side of the galvanometer until
the blades are free. Remove the cover and slide the harp out.
Unscrew the small screw on the spring-loaded clamp and remove
the spring with a pair of tweezers. Remove the spring from
the bottom plate of the harp in a similar manner. Feed the
new string attached to its spring, through the gap in front
of the ivory bridge on top of the harp and when it has cleared
the bottom gap, place the string in its appropriate slot, fit the
upper spring into the spring clamp and secure it in place.
Now release the tension on the upper spring clamp by un-
screwing the adjusting screw, fit the lower spring under the
lower spring clamping plate of the harp and tighten the
clamping screw. Re-adjust the tension on the upper spring
clamp and finally, by test, with the harp replaced in the
galvanorneter gap.
To test, the three-point relay, press the switch mounted on
the front of the instrument base to the start position.
This closes the motor, lamp and camera clutch circuits. Release
the switch and allow it to return to its central position and the
knife will operate. The motor will continue to run until the
circuit is broken, by depressing the switch to the "off"
position. if paper is being fed into the automatic developer
while the test is being carried out, keep The switch in the start position for at least
three seconds. Small pieces of paper, one
or two inches long will not feed through to the fixing bath,
and if they are allowed to collect in the guides at the end of the developing tray, will
eventually cause the belt to stop. Any
short piece of paper should be removed at once from the
developer belt.
Adjustment of the optical system
Slacken the screws holding The camera cylindrical, line
holder and remove it clear of the slot, Switch on the lamp.
Focus the galvanometer strings on the paper strip by the
lens nearest the developer.
Adjust the time motor rotor so that the image of a vane
of the time wheel is parallel with the camera slit, now focus
the vane with the lens nearest the time motor so that it is
sharply defined on the paper strip.
Check the focus of the galvanometer strings and replace
the camera lens holder.
