Job Number

0012-15

Equipment type

Portable 3-band radio

Maker + Model #

SANYO

Made in

Japan

Client Info

David Sammut, Evans Lab college.

Comments

Was given for taking parts, but decided to fix it.

BAD

1

Uncontrollable volume, always high and sometimes mute.

2

Volume control, aerial and broken

3

Tuning LED not functioning

GOOD

1

Powers up

Full repair description and observations

1

On opening the radio, it was noted the volume pot + switch was broken in two. Attempt to fix together the 2 parts were nearly successful as the pcb held together firmly with super glue, but the resistance carbon layer could not be joined together. Solder simply does not attach to carbon.

2

A new 10 kOhm potentiometer was bought. When coming to replace it, it was noted that it was not of the same dimensions of the original one. The following adaptations hade to be done:

 1)  The 3 resistance pins of the pot were broken away and instead 3 wires were soldered.

2)       The wire length was adjusted so that it passes under the body of the pot and enters the  

       pcb in the same manner as the original pot

3)       The pot was soldered in place and was held in place firmly but not rigidly.

4)       To increase strength, a measured piece of plastic was positioned under the shaft of the pot and stuck to the pcb with impact (evostick) glue. The purpose of this plastic was simply for support so that when force is applied while using the pot, it is pushed against the plastic.

5)       The shaft of the put was also longer, and the wheel was placed far away from the actual position.

6)       A hole at the centre of the volume wheel was drilled out and the wheel was inserted further inwards in the longer shaft so that the latter penetrated through the wheel.

3

The Led bulb contained one of the voltage supplying wires disconnected. It was soldered back.

4

The radio was turned on and the volume worked perfectly, and so did the tuning LED.

5

The aerial needed an adequate screw and bolt to hold it to the aerial base.

Repair summary

TOTALLY BROKEN VOLUME CONTROL POT

Precautions, fouls and advises

1

When opening a device, always study how it is closed. This radio had the back face held by screws and border plastic grips, and the front face could also be removed but only with plastic grips. Excessive pressure cause one of the switches to break slightly, but it was fixed without problems.

2

Also, the PCB was held with the case by 4 grips and also the varicap box (at the PCB) and its screwed-in-place tuning pulley which was above the case. Excessive force while trying to remove the pcb apart, could have broke the tuning pulley from he varicap. When removed, the pulley was held with the case by a piece of stick so that the tuning chord is not removed.