Job Number

0202-42

Equipment type

Portable radio / cassette player

Maker + Model #

AIWA

Made in

Comments

BAD

1

No radio function on all bands (FM/MW/AM)

GOOD

1

Good sound output on cassette mode

Full repair description and observations

1

Initially, the radio select switch and band select switch where inspected for dry joints and cleaned with contact cleaner, but did not solved the problem

2

While holding the radio circuit it was noted that sometimes the radio sound would be heard and so it was obvious that there was a sort of dry joint.

3

One by one, all solder pins of the radio circuit were melted to remove dry joints, but this did not solved the problem.

4

After several hours ticking on the circuit, it was found that the dry joint was somewhere near the AM/FM tuning IC BA4234. This IC, and  electrolytic capacitors involved with this Ic were replaced, but the problem persisted.

5

Later it was foun that if two pins of the IC were shorted, the radio sound will come up and remain for 1 to even 15 minutes and then it will go again. It required more hours of experimenting and checking components one by one, to find the faulty.

6

It was a red plastic package, 3 pin, band pass tuning filter ( marked around 751.25 kHz). Strangely, when a capacitor of 22nF was placed by experimentation instead of the filter, the radio began to work properely in FM and AM mode. The MW was not checked because it is not used. here.

7

Finally I changed the belts of the cassette player unit and gave a general service and cleaning to the circuit and casing.

Repair summary

SHORTED  BAND PASS TUNING FILTER