Grundig TK 30 Service Manual

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GRUNDIG 14x

GRUNDIG TAPE RECORDERS Models TK30, TK35

General Description: Dual-track, portable tape recorders with maxi-
mum spool diameter of 7 in. Model TK3o has two speeds (7% and 32 in. /sec.).
Model TK3 5 has the additional speed of 1% in. /sec.

Power Supply: A.C. mains, 110-120, 140-175 and 200-250 volts.
Mains current 500 mA. on 200-250 volts.

Valves: (V1) EF86; (V2) ECCSI; (V3) EL84; (V4) EL95; (V5) EM84.

Notes: Drive is obtained from flywheel driven by outer rotating cage
split-phase induction motor. Tape is friction driven between capstan
spindle on flywheel and rubber pressure roller, controlled by pressure
solenoid. Speed change obtained by moving endless plastic drive belt from
one pulley to another on motor spindle: on TK3 5 speed change from 3% to
1% in./sec. carried out electrically. Spools are carried on top halves of fric-
tion clutches, clutching being proportional to weight of tape and spool.
Digital type position indicator. Metal foils, as fitted to Grundig tapes, cause
motor to be switched off at end of tape. Second H.T. supply used to energise
relays and pressure solenoid. L.T.I supply for V1 is fitted with humdinger.
Microphone socket is polarised with 100 volts D.C.

H.F. oscillator frequency about 78 kc/s. R3 controls amplitude and C2
controls level of bias fed to head on the TK30.

Relay Operation: Switch on. R.I. energises via E, I and K. R.I.I
closes and holds R.I. R.I.2 closes and starts motor. To Record. Press
Record Button. N opens to remove muting of ECC81. M closes to energise
R.II via B. R.II.I closes, short-circuits R49 (on TK35, R.II.I is change-
over contact). R.II.2 changes over, reducing the holding current through
relay R.II. R.II.3 opens, removes muting of ECCSI. R.II.4 changes
over, selects recording characteristics. R.II.5 closes, connects H.T. to
EM84. R.II.6 changes over, couples radio L.S./Gram. P.U. input.
R.II.7 changes over, switches in record level control, R16. R.II.8
opens, removes short circuit on recording amplifier output. R.II.9 changes
over, removes short-circuit on input and earths one side of record/playback
head. R.II.Io changes over, connects input to V1. Press Start Key. D
closes, holds R.II. B opens, disconnects initial energising path to R.II.
C changes over, connects radio L.S./Gram. P.U. to diode output on
pin 3. E opens, removes initial energising path to RI. F closes, feeds H.T.
to oscillator. G opens, removes playback muting of ECCSI. H closes,
energises R.III via S and remote control socket, also energises pressure
solenoid via R.I.I, J, L, S, H and shorting contacts in remote control socket.
R.III energises, removing brakes. R.III.I changes over, limits current
through R.III. Tape begins to move. Press Temporary Stop. S opens.
Pressure solenoid, L2, de-energises. R.III falls off and applies brakes.
. Press Stop Key. Other buttons returned to neutral by mechanical
' linkage. A holds R.I energised. D opens and de-energises R.II. H opens