Technics STK 50 Service Manual

Page 2

ST-K50 -

I CONTENTS

Page
SAFETY PRECAUTION . 2 TERMINAL GUIDE OF IC'S,
ACCESSORIES ....... 3 TRANSISTORS AND DIODES .......................... 1 1
LOCATIONS OF CONTROLS . . . 3 CIRCUIT BOARDS AND ,
CONNECTIONS .. .. .. .. . 3, 4 WIRING CONNECTION DIAGRAM .................... 12,13 V
DISASSEMBLYINSTRUC ONS ......... . 5 BLOCK DIAGRAM 14,15
MEASUREMENTS AND ADJUSTMENTS . . 5. 7 FUNCTIONS OF IC TERMINALS . . 16
DESCRIPTION OF FL PANEL ........... . . . 7 REPLACEMENT PARTS LIST . . 17~20
SCHEMATIC DIAGRAM ................................ 8~11 EXPLODED VIEW .......... 21
I SAFETY PRECAUTION (rhls safety procautlon" is applied only In U.S.A.) 2
1. Before servicing, unplug the power cord to prevent an electric shock.
2, When replacing parts, use only manufacturers recommended components for safety.
3. Check the condition of the power cord. Replace if wear or damage is evident.
4. After servicing. be sure to restore the lead dress, insulation barriers, insulation papers. shields, etc.
5. Before returning the serviced equipment to the customer, be sure to make the following insulation resistance test to

prevent the customer from being exposed to a shock hazard.

0 INSULATION RESISTANCE TEST

1. Unplug the power cord and short the two prongs of the plug with a jumper wire.

2. Turn on the power switch.

3. Measure the resistance value with ohmmeter between the jumpered AC plug and each exposed metal cabinet part, such as
screwheads antenna. control shafts, handle brackets, etc. Equipment with antenna terminals should read between 3M9
and 5.2MSI to all exposed parts. (Fig. A) Equipment without antenna terminals should read approximately infinity to
all exposed parts. (Fig. B)

Note: Some exposed parts may be isolated from the chassis by design. These will read infinity.

Antenna
terminal \

Exposed Exposed /-
metal metal
part part
Ohmmetar Ohmmeter
(FIE/U (Fig.3)
Resistance = 3M9-5,2 M9 Resistance = Approx 00

4. If the measurement is outside the specified limits, there is a possibility of a shock hazard. The equipment should be
repaired and rechecked before it is returned to the customer.

I ACCESSORIES

OAC power supply cord OFM indoor antenna .................. 1 OStereo connection cables (short) ...... 1
(polarized) ........................ (SSA272M) (SJPK2203-2)
(SJA175-1)...(P)
(SJA175)...(PC)
Lang thin type
(SPT-l )