Job Number

0201-36

Equipment type

Video Recorder

Maker + Model #

Sanyo VHR 5200 G

Made in

Japan

Comments

BAD

1

Fast Forward and Rewind does not function

2

No Display (in complete darkness some light could be seen, but flickery)

GOOD

1

Powers up, and good Play, Rec, Cue, etc functions

2

Good picture and sound output

Full repair description and observations

FAULT 1: - No display (Flourescent vaccum type)

1

I noted dismantled the front section of the video, were I could make tests on the pins of the vacuum display. I noted that there were 2 main pins, (probably the voltage supply) and a set of pins where each corresponded to a particular segment/icon display. In fact the latter set came from a large IC (u-processor / display driver?) while the other two came from a different source. Following their path, these 2 pins came from the power supply section. Touching these 2 pins to earth via a 100 Ohm resistor caused the display to light up a little more

2

I opened the power supply compartment, which revealed that it was a switch mode power supply type. The particular pins that were being tracked came directly from a rectifying diode and filtering capacitor. From the SMPS. But there were other observations. The filtering capacitor was punctured, and the PCB was previously altered in this area by a previous technician.

3

I replaced the capacitor but I came to a problem. The polarity! The original faulty capacitor was connected with the +ve side at the earth and the –ve side with the diode. I assumed that the previous technician connected it in the wrong place and so I placed it the other way round. I also changed the rectifying diode – a 1n148. On powering, the result was worse. The capacitor began to produce white fumes within seconds. I turned the capacitor in the original position (+ve to earth, -ve to diode) and on powering the capacitor did not fume, and the display lighted up. The supply produced was of –50V

4

After few trials, the display went off again. The diode opened up. I checked from Maplin databook the diode and it was a signal diode with maximum rating of 50V. I needed a more powerful rectifying diode. I found out that the 1N400x series is the appropriate choice of rectifying diodes. I found an old 1n4004 (200V max rating) but strangely enough, it went open after some days.

5

I went to HE, and he advised me a 1N4007 – the stongest of the diode family. I replaced it and the display was OK. However I noted sparks of shorts in the chassis, which was bad ridden, burrowed and manipulated by the previous technician. The short was between a +66V from one track, and the –50V from a very near track. I opened the –50V track and used a wire to supply the voltage near the plug area. No sparks were now seen and it could be said the finally the display fault was fixed once for ever.  Probably, these pcb shorts caused the 1N004 diode to blow.

FAULT 2: - No Fast Forward or Rewind

1

This fault was  solved by a little luck and good observation.  Will operating the FF / REW I was observing the mechanism, and noted that the position of a particular small lever was  actually without function and useless.

2

Marks of friction on a neighbouring metal part showed that the gear has slipped. With effort I placed the gear in the expected original position and the FF and REW came to work well.

3

Unfortunately during the process I lost the timing and the Player was ejecting the video tape.

Fault 3: Timing of the mechanism and control step-mode motor

1

First I changed the timing belts. There were just 2 to change. The large one around the capstan motor and was very easy to replace, and a small one around the step mode motor, which was quite difficult to replace.

2

The video was set to stop mode by rotating manually the step motor until the T and S poles are in the full backward position.

3

Remove the metal casing over the step motor, motor nose gear and main gear. 

3

By means of a screwdriver move the tape loading assembly completely to the back side. Usually it will be by about 4 or 5 gear teeth ahead. It must be moved manually back to the last gear.

4

The step mode main gear and motor nose gear can be placed back in position.

5

Rotate step motor so that the video is in eject mode (as shown in the figure above), place a video, and rotate back step motor to make the video in stop mode. Power the video, and everything should work fine.

Repair summary

- NO POWER SUPPLY TO VACUUM LIGHT DISPLAY

- SLIPPED MECHANISM IN FF/REW  SECTION

1

When a rectifying diode is used to give a negative voltage from a transformer, the voltage is taken from the anode and the filtering capacitor is connected with the negative pole connected to the diode anode and the positive connected to earth.

2

The voltages found on  the Power Supply IC (STK 5973) and Output Plug of the Power supply unit when the video is on standby and stop mode are shown below

SMPS IC – STK5973

Power Supply Output Plug

Stand By

Stop Mode

Stand By

Stop Mode

Pin  1

     0V

      0V

Pin  1

   13.0V

   12.8V

Pin  2

  5.8V

   5.7V

Pin  2

        0V

        0V

Pin  3

 12.2V

  12.0V

Pin  3

   13.0V

   12.8V

Pin  4

 11.0V

 10.0V

Pin  4

        0V

        0V

Pin  5

 12.2V

 12.0V

Pin  5

 - 49.5V

 - 49.0V

Pin  6

 13.4V

 13.3V

Pin  6

 - 18.0V

      - 9V

Pin  7

 19.2V

 17.4V

Pin  7

 - 18.0V

      - 9V

Pin  8

 13.0V

 12.8V

Pin  8

   67.3V

   65.0V

Pin  9

 14.2V

 14.0V

Pin  9

     5.7V

     5.7V

Pin 10

 22.6V

 22.0V

Pin 10

        0V

        0V

Pin 11

    12.2V

   12.0V