Job Number

0109-30

Equipment type

HiFi Audio Amplifier Receiver

Maker + Model #

Technics Model No. Sa 106

Made in

Singapore

Comments

BAD

1

Does not power up

GOOD

1

N/a

Full repair description and observations

1

It was noted that the 2A / 250 V mains fuse was blown.

2

The power amplifier STK4833 pins were desoldered, a new fuse was replaced and powered. The fuse did not blow

3

With the aid of a schematic diagram, all pins of the Power Amp IC were soldered back, except the left and right output. The unit did not blow the fuse.

4

Finally the L + R output pins (5 & 12) were soldered too, and sort of surprizingly, the fuse did not blow again, but the sound was only on one channel and there was lot of noise when rotating the balance and volume control.

5

The balance and Volume pots were cleaned with the Electronic cleaning spray, and the noise was cleared off. The problem is that there is no sound output from one of the channel.

6

It was evident that the STK4833 IC was broken, so it was removed and the resistance across the pins were measured and compared. The pins of left channel and that of right channel were symetrical (left = pins 1-8, right = pins 9-16). It was found that there was 2 Ohms between the faulty output pin and the VCC input – which is totally abnormal. Now it was concluded that the Power Ampl was broken and need to be replaced.

7

The STK4833 could not be found locally so, it wsa ordered from telepart for a little less from 20GBP. The part arrived after 7 days, and was replaced. The amplifier worked perfectly with good sound on both channels

Repair summary

SHORT CIRCUIT ON ONE CHANNEL OF STEREO AMPLIFIER IC