HCDCP101 No Sound Sony Repair Kit KRC103S KRA102S Q313 Q330 Transistors

A no sound symptom is a common problem with the HCDCP101 HiFi. It is caused by failure of one or more digital switching transistors which leads to an incorrect voltage level on the mute line within the machine.

The problem is generally solved by replacement of two digital switching transistors. Both transistors are surface mount (SMD) types and a good degree of soldering skills is required if you wish to purchase the parts and repair the HiFi yourself. The repair is both cheap to carry out and normally 100% effective.

Now here's the technical jargon. The fault is commonly caused by Q330 going open circuit. This transistor is normally biased on and grounds the mute line. Please refer to the photographs showing the location of Q330 on the main PCB. Q330 is a digital switching transistor which is similar to a normal transistor except that two resistors are connected internally between the base and emitter connections. This type of transistor is commonly known as a digital transistor or a resistor equipped transistor. This particular device is an NPN type and has 2 x 22K resistors fitted. Diagnosis of this part is quite easy by measuring the voltage on the base, left connection, and the collector, top connection. The base should read 4V and the collector 0V but often the collector sits at 2V or so which causes the main amplifier to mute. Replacement of Q330 should solve the problem.

Additionally transistor Q313 can fail. This also causes an incorrect voltage level on the mute line. Q313 is also a resistor equipped transistor and is a PNP type with 2 x 10K resistors fitted. The correct voltage levels at Q313 should be base 8V, emmiter 8V and collector 0V. The collector connection is the mute line and must be at 0V in normal operation.

Both transistors are supplied and it is recommended that both are replaced. Replace Q330 first and fully test the machine. If there is still no sound then replace Q313. If the fault is cured by replacement of Q330 then it is recommended that Q313 is also replaced. It is best to replace the devices one at a time so that you retrace if you make a mistake.

Replacement of the devices is straightforward. Heat all three legs of the device with plenty of solder and a hot iron. The device will lift away easily as it is not bonded to the board.

Please remember though that  a good degree of soldering skills is required. Do not purchase unless you are confident and have some experience in the repair of electrical equipment. Please ensure the main unit is disconnected from the mains supply whilst soldering on the main board. Also check carefully for solder splashes before powering up again.

Both transistors are supplied in this kit.

To replace the transistors it is necessary to remove the outer casing so replacement should only be attempted by those who have experience in the repair of electronic appliances. It is important that the appliance is disconnected from the mains before any servicing work is carried out.