Nagra 4.2 Portable Analogue Audio Instructions Manual

							5. PINCHWHEEL LIFTER (stop + test only) 
 
6. LEVEL CONTROL (right) mic input 2 
 
7. LEVEL CONTROL (left) mic input 1 
 
These are the main level controls for the two microphone inputs.   
 
8. REFERENCE OSCILLATOR (push button) 
 
On the lower edge of the front panel, between the line and playback potentiometer and the mic 2 
potentiometer, there is the reference generator push button. When this button is pressed, a 
composite 1.1 kHz signal with a 10 kHz 9th harmonic at a level of approximately -8 dB is injected 
into the DIRECT chain of the recorder.  
The modulometer will show -8 dB. It is useful to record a short burst of this signal at the beginning 
of each reel of tape so as to enable the level of the playback chain to be accurately calibrated 
before the real recording is made. This also permits adjustment of the record head azimuth in the 
field without test equipment. At this point the subject of print-through should be mentioned. After a 
certain period of time, a recording may be copied (at reduced level) onto adjacent turns of a tape on 
a reel. This produces a perceptible echo during the silences preceding or following a strong sound.  
It is thus recommended to leave a pause of two or three turns of tape after recording the REF 
signal.  
 
9. LINE & PLAYBACK POTENTIOMETER 
 
This potentiometer is used to adjust the line input level when using the machine to record a signal 
from the line input (41). 
 
10. MANUAL/AUTOMATIC SELECTOR 
 
This switch allows selection of the sensitivity adjustment of the microphone inputs. In the MANUAL 
position the sensitivity is adjusted by means of the potentiometers (6) and (7). In the AUTOMATIC 
position 1 this gives ALC (automatic level control) to mic input 1 only and for both mic inputs in the 
position 2. 
 
11. LID CATCH 
 
12. MODULOMETER MODE SELECTION SWITCH 
 
This is an eleven position rotary switch allowing different information to be displayed on the 
modulometer.  
Each position is described below:  
 
X  Position not used. 
 
RX Indicates the level of the RF signal picked up by the antenna of the QRR 
receiver. (see note) 
SYNCH This indicates the phase shift between the pilot playback signal from the tape 
and the reference signal. Synchronism is correct when the needle is 
stationary.  
						

							 
PILOT PLAYBACK This indicates the level of the pilot signal played back from the tape. 
 
PILOT FREQ This indicates on the +4 to -4% scale of the modulometer, the frequency 
deviation as determined by the QFM frequency meter circuit (if fitted), 
between the pilot signal being recorded or played back and the 50/60 Hz 
reference. 
 
LEVEL The modulometer will indicate the level of the direct or the recorded signal 
on the decibel scale. 
 
BATT. RESERVE Indicates on the lower scale, the bold line shows the supply voltage reserve; 
the lower limit at the extreme left of the bold line represents 11 V. 
 
VOLT/CELL  This is a battery check indicating on the V/CELL scale of the meter and 
indicates the Volts per cell of the batteries. 
 
COMPRESSION Compression reading in decibels on the ALC compression scale when 
switch (10) is in the AUTOMATIC position. 
 
MOT This indicates the motor current. Maximum deviation = 250 mA. 
 
BIAS This indicates the record bias level on the V/CELL scale. 
 
NOTE : The QRT / QRR radio transmitter and receiver accessories are no longer manufactured. 
 
13. FILTER SWITCH 
 
This is a six position rotary switch, allowing different filter possibilities to be switched in or out. 
 
LFA 2 Low frequency attenuation, -8 dB at 50 Hz. 
LFA 1 Low frequency attenuation, -4 dB at 50 Hz. 
FLAT The machine has a linear response. 
HP 1 High pass filter, -10 dB at 50 Hz. 
HP1+LFA1 Combination of high pass and low frequency attenuation, -14 dB at 50 Hz 
and -3 dB at 400 Hz. 
HP2 High pass filter, -20 dB at 50 Hz. 
   
						

							14. MODULOMETER 
 
This meter is the visual indication of many functions and levels of the machine. The modulometer 
displays information according to the position of mode selector switch (12).  
 
The modulometer has 4 scales: 
 
1. Recording level in dB 
2. Frequency deviation in % 
3. Battery voltage (volts / cell)  
4. Compression 
 
 
15. PILOT INDICATOR 
 
This rotary SASS type indicator shows a white segment when the frequency (if the machine is 
fitted with the pilot system) of the pilot signal are correct. 
 
NOTE: This only indicates the presence of a correct signal being fed to, or coming from the head, 
and does not guarantee correct recording of the signal. This should be checked by 
switching the modulometer to PILOT playback (this does not function in the RECORD 
mode).  
16. SPEED AND POWER INDICATOR 
 
This rotary SASS type indicator gives a quick visual indication that the machine is functioning 
correctly and will indicate a white segment when this is the case. It will turn black whenever any of 
the following conditions occur: 
 
a.) The power supply voltage (batteries or external) becomes insufficient for correct 
operation of the machine. 
b.) The motor current reaches its maximum limit, in this case voltage and speed stabilizer 
circuit A22 requires the motor to run faster, but this is not possible because the automatic 
current limiter circuit has been activated. (If this occurs during normal operation, then 
contact your nearest NAGRA agent.) 
c.) WOW & FLUTTER is out of tolerance. (Contact NAGRA agent). 
 
 
Thus, when a white segment is indicated, the operator can be absolutely sure that the power supply 
is sufficient, that the motor current is correct, and that the tape speed is within tolerance. 
 
17. HEADPHONES OUTPUT 
 
This 1/4 jack type socket (type 297) is the headphones output socket accepting headphones with 
an impedance of anything from 50 Ohm to 600 Ohm. (Optimum value is 200 Ohm). 
 
18. HEADPHONES VOLUME CONTROL 
 
This small potentiometer is adjustable using a screwdriver and adjusts the level fed to headphones 
output connector (17). 
Position 1 is the minimum and position 6 is the maximum. 
19. REEL FIXING NUT 
  
						

							TAPE  DECK 
 
20.  SPEED AND EQUALIZATION SELECTOR 
 
This is a six position rotary switch permitting the selection of the speed and equalization of the 4.2 in 
both record and playback. 
 
 Possible settings are:  
 
 3 3/4  ips (9.525 cm/s)   
 7½  ips (19.05 cm/s)   
 15 ips (38.10 cm/s)   
 
For each of these speed selections there are two possible positions labeled I (STD) and II (LN) 
these correspond to different tape types. 
 
For best quality recordings the 15 ips speed is recommended.  
For normal recordings, the 7½ ips speed is available. The 3 3/4 ips speed is available for those 
cases where the length of recording time of the tape is more critical than the actual quality of the 
recording. 
 
21. MOBILE TAPE GUIDE 
 
22. PINCHROLLER 
 
23. REWIND AND FAST FORWARD SWITCH 
 
REWIND is possible with main selector (4) in any position other than STOP, assuming 
pinch roller lever (32) is in the fully open position. 
 
FAST FORWARD is possible only with main function selector (4) in the playback (with 
loudspeaker) position and pinch roller lever (32) fully engaged. 
 
The central position of this switch is OFF and this is the position that the switch should be in 
whenever the machine is not required to spool. Keeping it in this position will prevent accidental 
spooling of the tape when opening the pinch roller gate or playing back a recorded tape through the 
internal loudspeaker. 
 
24. & 34. TAPE REELS 
 
The 4.2 can be used with reels up to a maximum diameter of 5 (127 mm) with the plexi-glass lid 
closed, or up to 7 (178 mm) with the lid open. However, if the QSET option is fitted to the machine 
the 7 (178 mm) reels may be used with the lid closed.  
If it is necessary to use reels of up to 10 (254 mm), then the QGB large reel adapter may be used. 
See Accessories. 
 
25. & 33.  TENSION ROLLERS  
 
These two rollers keep the tape tension constant and ensure correct tape handling and positioning. 
During normal use neither of these two rollers should be at either end of its travel. If this is the case 
refer to the MECHANICAL CALIBRATION section of the service manual.  
  
						

							The two rollers can be replaced by either the QTIM or QLEN tape measuring rollers. The QTIM is 
supplied in the place of the take-up reel tension roller as standard equipment. QLEN instead of 
QTIM is optional. (To be stated when ordering). 
 
26. ERASE HEAD 
 
This is a full track erase head. 
 
27. STROBOSCOPE ROLLER 
 
This roller comes in two versions: 50 Hz (CCIR machines) and 60 Hz (NAB machines). Using this 
roller, it is possible to check that the machine is running at the correct speed, either in record or 
playback. This works at all speeds and uses the stroboscopic effect whenever a mains powered 
lamp is shone upon it. When at the correct speed, the bars on the roller should appear stationary. 
 
28. RECORDING HEAD 
 
Audio recording head. 
 
29. PILOT HEAD 
 
Neopilot head used for both recording and playback of pilot signals. 
 
30. PLAYBACK HEAD 
 
Audio playback head.  
 
31. CAPSTAN SHAFT 
 
Tape main drive. 
 
32. PINCH WHEEL AND TAPE GUIDE CONTROL LEVER 
 
This lever engages and disengages the tape from the heads and motor capstan shaft. It also moves 
the stroboscope roller and mobile tape guide in and out, to allow easy loading of the tape.  
 
When it is in the open position, rapid rewinding is possible. (This lever should never be left in the 
open position for long periods of time as this may cause a FLAT on the capstan shaft O ring).  
 
33. TAPE TENSION ROLLER (OR TIMER) (see 25) 
 
34. TAKE-UP REEL (see 24)  
 
 
Positions 36 To 49 see CONNECTORS  
 
 
  
						

							1.3 CONNECTORS  
36. MIKE 2 input 
 
                                                                                                           
 
1      = Input signal Ground 
2+3  = Balanced signal Input 
 
 
37. MIKE 1 input 
 
Identical to No 36 above. 
 
NOTE: The microphone inputs are convertible into symmetrical and floating line inputs by 
installing, in place of the microphone preamplifiers, preamplifiers type QPM-6 and using 
the corresponding potentiometer to control the input level. 
38. RX       Antenna input for QRR receiver. 
 
39. ACC (accessories) 
 
1. No connection. 
2. Ground 
3. Line input, current drive. Minimum source 
impedance 47 K Ohm. Current for obtaining 
0 dB at maximum sensitivity = 3.73µA. 
4. Tape speed correction signal input. 
5.  No connection. 
6. -10 V stabilized voltage.  
						

							40 MIXER  
 
For connection to external mixing console. (connector type: T 3478 corresponding plug T 3475/1). 
 
1. Input with fixed sensitivity, 560 mV to obtain 0 dB, input 
impedance 9 k Ohm. (2.5 Vpp to obtain +4 dB) 
2. -10 V stabilized voltage, Maximum current 50 mA. Noise level < 
5 V rms. 
3. Direct amplifier output, minimum load impedance 10 k Ohm, 
output voltage 560 mV at 0 dB. This is a monitoring signal to be 
fed back to the mixer. 
4. Unstabilized negative supply voltage. Available in all positions 
of the main function selector. Current drawn should not exceed 
2 A as this may blow the internal fuse with internal batteries. 
5. Playback amplifier output minimum load impedance 100 k 
Ohm, output voltage 560 mV at 0 dB. 
6. Motor stop control terminal. (connect to -10 V to stop motor). 
Operational in all modes except REWIND. it is not 
recommended to use this remote method in REC as this will 
magnetize the recording head and reduce performance. 
7. Ground (chassis) 
             
 
 
 
 
 
 
 
41 LINE INPUT  
 
Banana jack line input connector. Input impedance 100 k Ohm, input voltage to obtain 0 db on 
maximum sensitivity 370 mV.   Maximum voltage, up to 150 V. This is the value supported by the 
input resistance, but it is not recommended to exceed 10 V as crosstalk might be produced. Up to 
150 V has been foreseen is to allow for connection to a sound distribution system at 100 V nominal. 
 
42 VOL 
 
Loudspeaker volume control. 
 
43 MICROPHONE INPUT SELECTOR 
 
This is a four position microphone input selector: 
 
 DYN 200 = Dynamic microphone impedance 200 Ohm 0.2 mV / 
bar (2mV/Pa) sensitivity.  
 +48 = Condenser microphone, 1,5 mV/ìbar (15mV/pa) 
sensitivity +48 V phantom powering.  
 +12 = Condenser microphone, 1.5 mV/ìbar (15mV/pa) 
sensitivity +12 V phantom powering.  
 T = Condenser microphone, 1.5 mV/ìbar (15mV/pa) 
sensitivity +12 V T powering.   
						

							 
44. PILOT AND CLAPPER INPUTS 
 
1. Ground 
2. CLAPPER: Clapper oscillator control input (control voltage + 4 
to 14 V) or switching on of QRR receiver by connecting to 
ground. 
3. XTAL: Internal crystal pilot generator out, 50/60Hz. 
4. PILOT IN: Pilot signal input, impedance 5 k Ohm. Input level  
0.5 – 25 V. 
 
 
 
45. LINE OUTPUT 
 
The line output of the Nagra 4.2 is on the right-hand side of the recorder. The load impedance 
should be equal to or greater than 600 Ohm. When the Line and Phones switch is in the position 
Tape, the line output voltage is 4.4 V into 600 Ohm while playing back a tape recorded at 0 dB. 
The Nagra 4.2 can record at a level 4 dB higher than this, thus the maximum line output voltage will 
be 7 V. Unloaded, these voltages will be 10% greater. The line output uses two 4mm banana 
sockets. It is made up of by the secondary of a transformer and is floating. A banana socket 
connected to the chassis is available beside the line output sockets. 
 
46. GROUND (banana socket) 
 
47. LOUDSPEAKER 
  
						

							48. POWER PACK 
 
6 pole connector for external power supply and pilot signal output. 
 
 
 1. - BATT: Negative pole of battery compartment.  
 2. + BATT: Positive pole of battery compartment.  
 3. PILOT PLAYBACK: Pilot playback output. 
 4. SPEED CORRECTION: Tape speed correction input. 
 5.  EXTERNAL -12 to -30: Input for external power supply -12 
to -30 V negative pole.  
 6. -10 R: -10 V stabilized voltage output during record, I max 
100 mA 
 
 
 
49. FIXTURE FOR CARRYING STRAP/HANDLE 
 
50. CASE FIXING SCREW 
 
51. PLATE SHOWING RECORDING AND PLAYBACK EQUALIZATION.  
						

							2.1. POWER SUPPLY 
 
All models of the NAGRA 4.2 may be powered either by an external power supply (ATN-3) or 
alternatively by internal batteries. The 4.2 will accept voltages ranging from -11 V to -30 V with 
peaks of up to -35 V. The batteries are placed in the bottom of the machine and the polarity is 
marked inside the battery compartment. Turning the two fasteners with a screwdriver or a small coin 
opens it. All the batteries MUST be orientated in the same direction as indicated on the base of the 
battery compartment. 
 
The NAGRA 4.2 houses twelve D type 1.5 V cells having a maximum diameter of 33.5 mm and a 
length of between 59.5 and 62.5 mm. It is important to remember that corrosive material can leak 
out of flat batteries, causing severe damage to the recorder, and therefore it is recommended not to 
leave batteries in the machine during periods of storage. 
 
If leakage occurs as a result of leaving flat batteries in the machine, then wash the affected area 
with fresh water. The machine will suffer much less from the water than the electrolyte from the 
batteries. The external supply is fed into the machine via connector marked POWER PACK (48) on 
the right-hand side of the machine. Rechargeable batteries may also be used and can be charged 
using the ATN-3C (order no 14376), which includes the charger circuitry. 
 
The 4.2 will function when the power is as low as 12 V (at 15 ips - 38 cm/s) and down to as low as 
10.5 V at the lower speeds. (These figures correspond to a machine in perfect condition and 
working at room temperature). 
 
When using an external supply, selector switch (3) must be in the EXTERNAL position. It must be 
in the BATTERIES position when internal batteries are in use. It is not necessary to remove the 
batteries when working with an external supply (and vice versa). 
DANGER OF REVERSED POLARIZATION 
 
A reversed polarized power supply (negative to the chassis) WILL damage the machine. To reduce 
the risk of serious damage a diode is placed in parallel with the supply, which will be short-circuited 
in the event of, reversed polarization. If such an event occurs with normal dry cells, they will be 
rapidly exhausted and no further damage will occur.  
 
On the other hand, certain accumulators are capable of supplying sufficient current (in excess of 8 
amperes) such that the internal wiring of the machine will become hot enough to cause its insulation 
to decompose. This will then liberate gas, which causes considerable corrosion. If this happens, 
contact your nearest NAGRA agent immediately. 
MEASURING BATTERY CONDITION AND POWER SUPPLY VOLTAGE 
 
BATTERY RESERVE 
When the Meter Switch is put into the Batt. Reserve position the meter will indicate the difference 
between the power voltage available and the power, which the Nagra needs. Often the two voltages 
will fluctuate. The device will take into consideration the lowest instantaneous voltage and 
memorize this. This detail is important, for the average voltage of a power supply can be sufficient 
but momentary drops in the voltage can happen and drop lower than the required minimum. 
New batteries will give about 18 V whereas the Nagra can be powered by up to 30 V. This explains 
why, with new batteries, the needle of the meter will only indicate about 40% full scale, when it is 
switched to Batt. Reserve.