Job Number

0011-12

Equipment type

Portable radio

Maker + Model #

Omega

Made in

?

Comments

BAD

1

Tuning pointer non operating

2

Weak tuning (due to broken aerial)

3

Uncontrollable volume on adjusting the volume control

GOOD

1

Powers up and tunes properly on strong signals

Full repair description and observations

1

On opening the radio, it as noted that the tuning pointer system was the string/pulley type. The string was jammed in some way and prevented the pointer to move.

2

While trying to fix the problem, the eroded weak string gave up and broke.

3

The first attempt was to join the string again with super glue, knots and melting the nylon with a lighter, but it was all in vain - the string broke on extra tension

4

I tried to replace the string with ordinary home string (spag) but was not of the same material type and hence it did not worked

5

The only solution was to weld the tuning pot shaft with the screw of the varicap wheel, and drill a hole over the centre of the wheel from where the shaft projected through and to which the tuning pot was fitted to.

6

With the braising skills of my father, the tuning shaft was joined with the varicap wheel screw

7

In the meantime a piece of nylon string of the same original material was obtained, and this was successfully wound around the varicap wheel and pulleys - the tuning pointer was back moving well to and fro.

 8

Contact spray was used to remove dirt from the volume pot, and hence solve the uncontrollable noise problem

9

Finally a small radio aerial was fixed in place of the broken one.

Repair summary

1)     CONNECTED TUNING KNOB DIRECTLY ON VARICAP

2)     FIXED NEW AERIAL

Precautions, fouls and advises

1

It is a very difficult task to wind back the tuning string when it breaks up. The following are small hints which I found useful:

-          Better to use a new string of same material rather then joining the old one. If the joint was made with super glue, it would not be enough strong when applying tension, while if it is joined with a knot, the length of the string becomes shorter by about 2mm and this is enough to make it impossible to coil the string in place.

-           

-          Cut a piece of string, about 20% longer from the original and tie one end with the hole of the tuning wheel.

-           

-          Study how the string should be placed over the pulley / tuning pot shaft.

-           

-          For example there should be at least 3 or 4 turns around the tuning pot shaft.

-           

-          Wind the string over the pulley system.

-           

-          Attach the spring at the other end of the string but do not tighten the knot.

-           

-          Move the spring within the knot until it is in a suitable place. In case of doubt make the knot tight in a position, which is little (2mm) longer.

-           

-          Attach the string with the tuning wheel. If it is not tight enough (string bit longer), remove string, and make a free knot so that it shortens a little the string. The knot should not be placed on a position near pulley of visible by the user. Preferably near the spring itself.