Job Number

0201-34

Equipment type

CD Player

Maker + Model #

Pioneer PD-5700

Made in

Japan

Comments

Circuit Diagram available

BAD

1

Completely dead, not even standby LED lights up.

GOOD

1

N/a

Full repair description and observations

1

235V a.c was found entering the a.c. transformer which had an internal resistance of 250 Ohms. Suspected that this may be high since the buzzer test did not buzz up, indicating no continuity. However there was a.c. output from the transformer, and the main rectifying capacitors had approx 16V across. Transformer probably was good

2

It was found that the the 5V and 12V supply voltage in the circuit were missing. These were coming from a special dedicated IC which its function was to give steady voltage Vcc and –Vcc supplies of 5V and 12V. This IC - which was a Mitsubishi M5296P costing about LM14 - was not supplying these voltages.

3

. After fetching the datasheet from Mitsubishi site, the input pins of the IC were found, which consisted of a –ve input and +ve input of about 16-20V The negative input was reaching the Ic, but the positive did not! The input supplies came directly from 2 reservoir filtering capacitors, which both had the expected voltage on them. However, in series with the positive supplying capacitor and the input of the Mitsubishi IC, there was a two pin IC that contained 18V on one side and 0.4V on the other side. This Ic, marked T10N, was found to be open circuit.

4

On further investigation, the IC was found to be an electronic fuse (thanks to HE electronics). Mapp electronics was able to supply me the last 2 of these. HE advised me that I can use a 0.47 Ohm fusible resistor in place of the electronic fuse.

5

Since MAPP was closed, initially I opted for the fusible resistor advice, and the CD turned on and began to work normally. However I noted that the spindle motor was ‘lazy’ and sometimes it did not started up, with the result of the CD player not identifying the CD. However if you help the spin manually it will catch up and continue to work normally.

6

I decided to buy the electronic fuse, and the problem did not solved up. I then tried to vary 4 variable resistors, which had control and adjustment on the focus, tracking etc. This was a fatal error because I lost the precise setting of the 4 variables and it was not easy to bring them back to the original position. With luck and lots of patience, the original setting was restored and the CD was working back to normal operation.

7

The ‘lazy motor’ symptom however remained and I was hopeless. At one instance, when the motor was making an effort to start up, it blew again the electronic fuse! I replaced it with the last one available I had

8

With no options left, I finally greased the spindle motor, shafts, and mechanical gears of the CD so that this may decrease friction and resistance load on the motor. It was an excellent idea because the motor never failed again and the CD player was reading and playing CDs normally. I tried to reload CD for many times and I never got a fail, so I can safely say that the fault was eliminated.

9

I assume that the following had taken place: Dust and dirt may caused minute blockage in the motor The extra stress on the motor demanded more power and so more current, and this extra current may have blown the sensitive electronic fuse.

Repair summary

ELECTRONIC FUSE OPEN CIRCUIT – MOTOR LAZY TO START UP

Precautions, fouls and advises

1

CD players most often contain variable pots to adjust various settings and voltages regarding lens power, focusing, tracking, speed etc. These pot settings are very precise and usually require a tedious procedure to adjust to the ideal position, with the need of an oscilloscope. Changing the pot value to test up if it will effect the symptom is a good idea, but it is IMPORTANT to measure by an ohmmeter the original resistance (with the set powered off) so that they can be easily turned to their original setting. 

1

Resistance of primary coil of an a.c. mains transformer is usually 80-300 Ohms. This may fail the continuity test with a voltmeter, giving the false interpretation that the transformer is empty

2

Fuses can be in the form of electronic IC. They have the package of a small transistor, but have 2 pins instead of 3. The nomenclature is usually Txx, eg T05, T10, T20 and each has a specific current limiting value, usually small. For instance, the T10N is 0.4A