Technics SA-GX550 - PROTECTION CIRCUITRY AND REPAIR PREPARATION; Protection Circuit Issues and Repair Safety Precautions; Component Terminal Identification Guide

SA-GX550
Mi PROTECTION CIRCUITRY
The protection circuitry may have operated if either of If this occurs, follow the procedure outlines below:
the following conditions is noticed: 1. Turn off the power.
¢ No sound is heard when the power is turned on. 2. Determine the cause of the problem and correct it.
eSound stops during a performance. 3. Turn on the power once again after one minute.
The function of this circuitry is to prevent circuitry
damage if, for example, the positive and negative Note:
speaker connection wires are “shorted”, or if speaker When the protection circuitry functions, the unit will
systems with an impedance less than the indicated not operate unless the power is first turned off and
rated impedance of the amplifier are used. then on again.
Mi BEFORE REPAIR AND ADJUSTMENT
Disconnect AC power, Discharge both Power Supply Capacitors C703 and C704 through a 10Q, 5W resistor to
ground.
DO NOT SHORT-CIRCUIT DIRECTLY (with a screwdrive blade, for instance), as this may distroy solid state
devices. After repairs are completed, restore power gradually using a variac, to avoid overcurrent.
Current consumption at 50Hz/60Hz in NO SIGNAL mode should be shown below with respect to supply voltage
230 V/240V/110— 127 V/220 —240V.
Power
supply
voltage
AC
230V
AC
240V
Re
toc
ter
ihe
o35
240)
50Hz
|
200~500mA
220~540mA
400~1000mA
200~500MA
Consumed current 50/60 Hz | SOHz | | 50H | SOHz | | 50Hz |
| 60Hz | 160~400mA | 60Hz | 176~432mA | 60Hz | 320~800mA | 60Hz | 160~400mA
Mi TERMINAL GUIDE OF IC’S TRANSISTORS AND DIODES
LC8A012A5328 M50198P M5218AP_—_—s|§ 8 Pin | AN6654F 14 Pin
LA1830-H3 | 24 Pin| LA2730 | 16 Pin |
[Lo72i8 | 24 Pin}
BA6218
rroeziaP__ [16 Pin |
rre9212 [20 Pin]
rroatesn [26 Pin]
AN65s6-FSG | 8 Pin)
fupcas70¢ | 8 Pin,
hMc140946CP [16 Pin]
2$C3327ABTP
2SA1309AQSTA
2SC2785FETA
2SC2787LTA
2SC3311AQSTA
UN411FTA
UN4113TA
UN4211TA
Ee UN4213TA
UN421FTA
2SC3940AQSTA UN4214TA
EC
B
2SJ40CDTA
2S8621AQSTA
2S02631QRSTA
LNO18304P MA165TA
MA7O0ATA
1SS291TA
1SR35200TB
2881187DEF
2801761DEF
MA4030MTA
MA4039MTA
MA4150MTA
MA4220MTA
Ca
ae Cathode opp lia Cathode MA4240MTA
A MA4056MTA
MA4062MTA
MA4068MTA
MA4075MTA