Technics SU 300 Service Manual

Page 2

I LOCATION OF CONTROLS

Tone control

CID/aux inpu t
Tuner input--

Phono input-

Power switch/indicator

Speaker switch
1 1 off, - on)

SW Viiyhw m w sum.

' 'umumiumimi""

],

Tape monitor selector

Volume control

CD/aux tuner phono

Loudness switch
l 1 off, A on)
-alanee control

Speaker terminals

--Voltage selector
(For [XA] and[XB]areas only)

(1 source, -tape/ext)

Input selector

.-AC inlet

@[ $8 ggleeeel ii 0
\=( \=(
Ground
T [ext-{Recom- [ |-(Switched)-]-ACO|[HM? d
ape (For XA an
Playba°kfl T-Il-I-lUnswitched) [X31 masonlvl

0 The power supply for this unit varies depending upon the areas. Also, the parts used for power supply are different.
So, refer to the Circuit diagram and replacement parts list.

[XA] and [X8] areas are provided with voltage selector and AC outlets.

* 240V (50/60Hz) for Australia and United Kingdom.

* 220V (SO/BOHZ) for Continental Europe.

" 110V/127V/220V/240V (BO/BOHZ) for other [XA] and [X8] areas.

* Phono input capacitance is about 150pF.

PROTECTION CIRCUITRY

The protection circuitry may have operated it either of the
following conditions is noticed:

o No sound is heard when the power is turned on.

0 Sound stops during a performance.

Thelunction otthis circuitry is to prevent circuitry damage if, for
example, the positive and negative speaker connection wires
are shorted", or it speaker systems with an impedance less than
the indicated rated impedance of this unit are used.

I BEFORE REPAIR

1. Turn off the power, Discharge both power supply capacitors (0603, C604, SBOOuF) through a 10 ohm, 5W resistor
to ground. Do not short between C603 and C604. It may damage the capacitors.

2. After completion of repair, slowly apply the primary voltage by usmg a variac to mod over current. Current con-
sumption at BOHZ/BOHZ in no signal mode should by shown below with respect to supply voltage HOV/127W 220W

If this occurs, follow the procedure outlined below:

1. Turn off the power.

2. Determine the cause of the problem and correct it.

3. Turn on the power once again

Note:

When the protection circuitry functions. the unit will not operate
unless the power is first turned pit and then on again,

240V,
Power supply voltage AC110V Ac127v ACZZOV AC240V
50HZ 95 ~ 190mA 80 ~ 180mA 47 ~ 94mA 43 ~ 86mA
Consumed current
60Hz 42~ 84mA 38~ 76mA