Franc Zabkar wrote:
On Wed, 26 Apr 2006 21:01:22 +0200, real_pixie
put finger to keyboard and composed:

Hello Guys,

I have a Sony DAV-SA30 DVD surround system. It has been making a
ticking noise through the speakers so I thought I'd have a look inside..

I found that the power supply module, 1-687-086-15, is supplying
34.7volts on it's 27v output.

The 27v supply is high wattage to the amplifier card, it goes at follows:

+ from rectifier goes to the pin 1 of Q904, a 3 pin chip. Pin 2 of Q904
goes to the connector that supplies +27v to the amp. Pin 3 has a thin
PCB trace going to various surface mount components presumably to
control the voltage level.

I am trying to locate the fault but cannot identify Q904, it is labeled
PK K1189 33.

2SK1189 MOSFET?

http://www.sanken-ele.co.jp/en/prod/...f/2sk1189e.pdf

What do you think is my best bet for repair? Maybe a new voltage
regulator bypassing this Q904?

Check the drive to the gate of the MOSFET. Check for a D-S short
circuit.

Any ideas gratefully received!
Kris.


- Franc Zabkar

Thanks Franc,

I have removed the MOSFET from the board and tested the resistance
between pins, D-S is approx 1 ohm, which I understand would be correct
for a MOSFET, the gate pin has only 10 ohm resistance to both the D and
S. I think this may be the problem, I believe MOSFET G-D/S resistance
should be very high.

I'll get hold of a new MOSFET and give it a try. Do you think the 34v
going back through the gate will have damaged the drive circuitry?

Thanks for your help so far,
Kris.