Ferrograph 420 Owners Manual

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THE MANUAL

OF THE

FERROGRAPH

SERIES 420

THE F F. R ROG RAM | COMPANY LTD.

K4. HIKCKFRIARS ROAI) ' LONDON S.P.I.

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EERR( )GRAPH MAGNETIC TAPE RECORDER
SERIES +20

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Noun-On twin tract recorded tapes made on a standard tecottlet such an the
Pampapll model 4A, the lower track will be heard backwards if it is attempted to replay
it an above. The cottect ptocodute is to invett the tech and replay it through the quiet
trad channel as is done on a standard instrument.

(e) Slanultaneoua twin channel recordings. e.g.. Stmo

Fotthiaofmmemaddifionflexutnalamplifietmdloudspuketwiflbetequimd
and it should be connected (without a mains earth ot'ita own) [0 the lower melt output
itch.

Taking that a mottled two: track stereo tape.

Arrange the loudspeakers at the recommended spacing given by the tape manu-
Eaetums. [Home is mentioned. 7to lofeetapart is the usual distance).

0n the model 424, check that the tnonitm head lever. (I. in Fig. 2). is fully forward,
La. head is in "down" position.

Check panel controls.

Knobs l, 2, 5, 6, at zero.

Knobs9and lounncedtoayi.

Switch 3 to 7'5 for tapes of Ametican origin or with NARTB characteristic. To
7'5 X foe tapes ofllutopean odo'n or with CCIR characteristic.

Switch 4 to TAPE" position.

Run the tape, and adjust knobs 9 md 10, together with the external amplifier gain
controls, to the desired output level.

Nor: z-lf the external amplifiers have exactly the same amplification, a balmced
outputshouldhcobtainediflmolnliand IOatesettothesamedialtending. 'l'hitwill
apply over nsost of the scale but slight individual odiuttittents may be may if theit
setting is at eithet end.

The model 424 (not the 422) will also replay : melt pie-recorded stereo tape, and
the only change necessary [tom the above is to move the nimitot head lever (L) to the
buck" position. 1).. head is fully up.

5. TOREWIND

Set the main function iI'lldI to the wind back position, neat to record. The automatic
stopamtwilltettactfromtheupeuidistlnnfweimpaauwwlunhnwindingsothatitis
advisable to remain in the immediate vicinity of the instrument during th'n short operation.

Sun the mechanittn in the usual way when the up: will be tewound at high speed. If
theplaybackpuncotttmlsflmbsiland I0)havcbeenlefiadtmedahighspeedgublodsmmd
will mutt as the tape panes over the miter head, this is ohen useful for cueing or plane
locationonthetape,butifundutredoneotbothhtobuhouldhetetutnedtoaem.

The indicator clock will slowly return to the tending it had at the commencement of
recoding or playback and at this point the rewind may be stopped by depressing button (D).

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(G)

(I) Stereo recordlng (microphone;-

This requires m separate microptmne: ur a spaial um unit stereu microphone.
With the former, results will vary with the separation. and angle of the individual
microphone heath (ifribbon type). and usually some expainienung will be necessary.
With the stereo microphone, the only variable is the positioning of it. relative to
thethobeucmMIheotherfiaetmbdngpre-deoemmed.

Tomaheamudingtheprooedmissimflutothatdesenbedfmnndednnml
workinguneptthubothtracbwillbemkingrogether.

lf headphone monitoring in enviaqed, each earphme should be connected
:epentely touch mnput ind: on the rear panel.

Thepaneleontmlathouldheminitiallyasfnllam:
Knob. 1,2 zero(ak09.and l0,ifnornonitoring).
Knob 3 to speed dam

Sllildt 4 m TAPE".

m 7 to STEREO.

Turn the main funmon switch to "RECORD" and set peak level meter to m
(check with switch 8 on UPPER and LOWER).

th the micmptume working, and switch 8 on "UPPER". advance knob 5
unrilthemeteriswningtofloniuwale.

Set switch to LOWER and advance knob o for the same result. Note counter
(E) railing and start tape running.
(ii) Stereo recording from dine

Once again, most of the notes out-2mm; disc recording on w: channel apply.
nae maternal amplifier and speakers for neutering. Ind SWITCH 4 will compare
ORIGINAL" and RECORDING" on both channels.

Special Applicant:
1: is recommended that the preceding pages are studied before my of the following

applications are attempted, as in general, they are minhinatiorn, or simple vm'ama of
stutdard recording techniques.

(5)

Recording two sip-la lint-luneouly on one truck (nailing)
ThefuuimpummthingistonntethatonesignalmustbemmV(minore)and

theotherbetueenZandSOmV. lfthehnuismfltanSOmVJtanetbee
reducedbyalimple potentiometer arrangemennbutthisrnlm hedone before injection
intoinputl.

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'I'ECl'lNlCAL SECTK ).\'

The following page: are entirely technical in nature and devoted to a descript'tm of the
main duign features together With test and alignment procedures in me of need.

II. DESIGN DETAILS
(a) The mechanical aalt

The mechanical unit is wholly contained on the hinged top deck of the instrument.
Three mots are employed. One, running counterclockwise when energized, takes up
the up: after having paased through the capstan assembly ; the recond. running clock-
wise when enerp'ud, rewind: the tape after recording. During the record and playhad
functions this motor is partly energized to maintain a small hack tension on the tape.
The sole function of the third minor in to drive the capstan and flywheel asaernhly. It
ia a split phse capacitor type induction motor with sufieient reterve of power to make it
relatively insensitive to small changes of applied voltage or load, and its speed therefore,
within certain limits. is controlled only by the frequency of the mains supply.

This motor, running clockw'ne viewed from its spindle end, carries a stepped pulley,
against either step of which a neoprene rimmed idler wheel driws a heavy flywheel.
Rigidly coupled to this flywheel is the capstan proper which has a brass brash to which is
bonded the landed neoprene traction surface

The assembly is mounted on greased angular contact hall races, rendering any
regular lubrication unnecessary.

Threeseparateheadtaretuedunthenktdel422.thacarethetwotrackerasehead
X4 followed by the We track stereo record head X5 and the two tract stereo monitor or
playback head X6.

0n the model 424 the only clung: is the substitution of a quarter trad: playback
heal X1 for X6.

The era: head is mounted rigidly on the base plate but small shims are usually
employed underneath for exact adjustment of its height.

The record head is screwed to a small plate which pivots on two cone pointed sue
onitsoentreline,oneuthefrontandthcoiherattherear. Thesescrewsfitinwtapped
holes in the plate and are fixed by 6 IA locknuts. they are used to determine the height
aettingol'thereooedhead. Theplateandheadnuyberockedtweratmallanglehya
screw in the from right marten This is to ensure that the gaps in the upper and lower
track sections of the head are exactly at right angle: to the tape path, thus falling into line
with other instruments. and guarantees that recordings made With it can be played back
without any lens of the high frequendes which would amur if the gaps in the more and
playback hearts we at drfl'erent angles.

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