Ferrograph 702 Service Manual

Page 1

series seven

L OPERATORS HANDBOOK

FEHROGRAPH

Page 2

MID-ODD. ISSUE 4

OPERATOR'S HANDBOOK

Farragmph

SERIES SEVEN. MK 2

SEFIIAL NUMBER 78.800/2 ONWAHDB

THE FERROGRAPH COMPANY LID.
IONDON AND SOUTH SHIELDS

Page 10

LOWSPEMER LOW LEVEL
OUTPUT OUT?

UNE
D C FUSE WRIT
mun
OUTPUT

G. 1 REM PM "0740

Outputs
Loudspeaker

The Loudspeaker output will provide up to 10 Watts undistorted
output into a 15 or 81) external loudspeaker for high fidelity listening.
Plugging into this socket automatically disconnects the internal
loudspeaker and the enamel loudspeaker signal is then governed by
the Output. Bees and Treble controls.

Note-As with other trenslormertess power output stapes. care
should be taken not to short the speaker leads to each other. as this wrll
probably overload the amplifier and blow the DC. fuse. The faulty
connection must be corrected and the lune replaced before the amplifier
will function again. On the stereo models. there are two fuses - one
for each channel - so that only one channel will be inoperative when a
lose blows. However. the oscillator is powered through the Upper
track fuse and should this blow. it will not be possible to record (even
on the Lower track) until the Upper track 0.6. fuse is replaced. Oh no
eccount should anti-surge or delay fuses be used.

Amplifier

It it is required to use an external amplifier and loudspeaker. either
instead of or together with the internal amplifier end loudspeakers. it
may be led from the 6000 output. This is an emitter follower gluing
approximately 2V slgnel at 600 (I impedance from a lull depth recording.
and while the im dance into which it is led is not critical. impedance
at less than D will reduce the output available. If the intemel
loudspeakers are not required. the Output control can be turned to

zero as the 6000 output is independent of the Output. Bess end
Treble controls.

16

FIG 4. llill PAKL STEREO

ll it is required to utilise the internal tone controls. the amplifier
may be led from the low lml output (300niv at 2-5lt ll) provrdod
that the amplifier input impedance is 10K it or higher. Again. ii the
internal loudspeakers are not required. they can be silenced by turning
down the Output control However. the Signal is modified by the Bass
and Treble controls and this is itselul when retrieving tapes recorded
to e characteristic other than that ol the recorder. On Models 702 and
704. the Low Level Adjustable output could be used. when the srgnal
can be adjusted by the Output control.

Headphones

If it is required to use headphones. these should be plugged into the
Loudspeaker output Although their impedance is not critical. it IS
recommended that this be 00!) or higher. as wrth lower impedance
headphones the Output control setting may need to be very low indeed.
in View of the large output power available.

DECK OPERATION

The dock ol the Series Seven Ferrograph has been desaaned [or single
knob control at the major operations, the Function knob being Situated
at the from left of the deck. as shown In Fig. 5. It has tour posnions.
"Fast". "Stop". "Pause and "Run" and should be at "Stop when
loading or adjusting the speed controls.

At the centre of the deck. adjacent to the turns counter. is a small
lamp labelled "Reset". This lamp is operated by the "fault" relay and
lights up whenever an incorrect setting occurs. or ii one of the automatic
stops operates In either event the Function swrlch must be returned to
"Stop (Reset) and the cause ol the lault removed bolero the lamp Will
90 out. thus indicating lhal the deck is again ready lot operation.

17

Page 15

be avoided or the contrast between loud and soft passages may be
lost altogether.

Microphone Characteristics

Making a "live recording With a microphone requires close attention
to detail for optimum results. as the quality of the recordi no is dependent.
among other things, upon the typo of microphone used. the location of
the microphone and the acoustics of the room or surroundings. A
primary property of the microphone is its directional characteristic. and
there are three basic types. The omnrdiroctionel microphone picks up
sounds aquellylrom all directions and is very useful for recording
sounds from several separated sources. co. 8 group of people sitting
around a room. The bidirectional microphone has a "frgure-of-eight"
response and picks up sounds from the front and back. but is largely
insensitive he sounds originating at the sides. and this can be very
useful in eliminating unwanted background noises. The third type has
a unidirectional or cardioid response. picking up sounds from the front
and towards the sides (usually over a 130' are) but being insensitive
to sound originating towards the rear. This can be very useful for
recording in locations with high background noise and also for stage
and concert work in eliminating noises from the auditorium.

While most types of microphone. except high impedance and crystal
types. can be used with the Series Seven Ferrograph. it is pomtlas to
restnct the overall fidelity by using the very cheapest Havrng regard to
all the factors involved, the most suitable for general purposes are the
moving coil (dynamic) and ribbon microphones. To match into the
microphone input. they should be medium impedance (ISO-2.0000).
but low impedance microphones can be used With a low-immedium
matching unit (TA/MIMI. page 14).

Microphone Phantom

The above characteristics are for "free field" or open air conditions,
but when used indoors. reflections from plane surfaces such as walls and
windows can modify the effective directionality of the microphone and by
suitable placement each of the above type: can be used in most
situations. It desirable. the room reflections can be decreased by drawing
curtains over windows. hard furniture. etc. or increased by removing
cushions. soft furnishings, etc. and by rolling back the carpet. A certain
amount of experimentation may be necessary to find the best position
for the microphone. but as the tape recorded during this process can
be used again for the recording proper. this is no great hardship. It is
advisable to keep the microphone a reasonable distance from the
recorder a.g. about 5 ft, or to orientate the microphone (it directional)
so that the recorder is in an insensitive part of the microphone field. as
a certain amount of mechanical noise from the moving parts (especially

26

the tape) is inevitable. and for highest quality recordings all back-
ground noise should be avoided.

Use a! Microphones

With regard to the detailed use of a particular microphone. the
indindual manufacturer will issue appropriate instructions depending
upon its type and directionality. However. it is usually undesirable to
speak into any microphone unnecessarily closely (particularly if It
has been kept in a cold room) as condensation may affect the perform-
ance and unless the rmcrophona is specially treated may eventually
cause corrosion. With ribbon microphones clou taflnn should always
be avoided as this causes bass eccentuation. but shoul it be necessary.
due to high local noise. speaking should be across the front at a
minimum of 3". 0n no account should a ribbon microphone be blown
into to check that it is functioning as this may damage the delicate
ribbon. and for this reason. it should not be used out of doors on a
very windy day. in general. all microphones should be treated with the
care they deserve and severe shocks should be avoided.

Monitoring

As all Series Seven Ferrographs have separate record and replay
heads, it is possible to monitor the signal off the tape whilst recording.
and this can be done aurally (loudspeaker or headphones) by setting
the Output switch to "Tape". The replay signal can also be observed
on the meter if the Meter switch is set to "Output".

On setting the Output switch to Tape". then "Source". and back
again. the repley and record sa'gnais can be compared auralfy or visually.
Their levels are normally set or Ferrotape type B such that the meter
indication on Tape" is the same as on "Source" for easier comparison
of the signal quality. and hence the record signal level can be checked
on the meter even with the Output switch at "Tape. This will apply
to most of the standard good quality tapes. but if it is required to use
tape which has an output markedy drfferent from Ferrotape. it is possible
:108 readjust the "Tape" level as outlined in the Technical Section. page

The recording can be monitored aurally by a loudspeaker (internal or
external) or by headphones connected as on page 17. or alternatively
an external amplifier and loudspeaker could be used. When using a
microphone for recording. the loudspeaker must be silent to avoid
acoustic feedback (see page 25). and audible monitoring must be done
using headphones If these are not available the meter can provide a
useful check that the signal is being recorded by setting the Output
switch to "Tape" and the Meter switch to Output.

On Fast Wind. audible monitoring can also be used for place location
on the tape (Output switch at 'Tepe"), when the signal is heard as a

27