Sounds most of all like a problem in one of the IF-circuits.
Check the BF160s.
Perhaps even in the FM frontend. Check the AF106s here.
DC voltage readings will often tell you a lot.

Don't try to calibrate or adjust anything. The calibration rarely goes out, it's usually something else.

Martin

Thanks Martin, that was quick! I will open the radio up during the week and report back the findings.

Thanks gain

David

Hi Martin Et al

Well I've had a look inside the radio and the model number is Beomaster 1400M 2105 series 09. This has an 8002048 Main Circuit Board and an 8050034 Tuner. These appear to have slightly different transistors to the original units. I have checked all the relevant voltages as Martin suggested, they are listed on the attachment. Basically all the voltages apart from one are close to the specified voltage and I assume bearing in mind component tolerances and my test meter accuracy that they are acceptable?

The one issue is the TS88 (1) in the Tuner where there is no voltage on the s connection. Presumably this indicates that the component is U/S? The diagram shows a 2N5245 as an alternative. These seem readily available so I will order a couple.

I also measured the main supply rail voltages, the 15V supply to the Tuner measured 14.95V, the 20V rail measured 19.8V and the 30V rail measured 29.7V. Again I assume acceptable?

I will keep you informed of progress when the components arrive. In the meantime if anyone has any further suggestions or comments please feel free to chip in,

David

Some success! I have replaced transistors TIS88(1) and TIS88(2)in the FM tuner with 2N5245 alternatives and I now have 0.6V on the source pin rather than the 0V I had previously. This has improved the radio to what I would expect, the FM stations are much stronger and I get good reception even with only a short wire in the antenna socket. The tuning meter now deflects to almost full scale on a strong station and the sound is great with no hiss, so good progress.  Thanks Martin for pointing me in the right direction.

Although I am sure the stereo is working the Stereo indicator lamp doesn’t work. Whilst the FM tuner was out of the way I should have checked the stereo lamp although I am pretty certain it has fused. There seems to be 29.5 volts across the bulb holder whenever the radio is turned on – even on other than FM wavebands. I need to bottom this out but I am enjoying listening to the radio so some motivation is required. Both the tuning needle and tuning meter illumination bulbs had fused, I happened to have some 3mm 6V bulbs that fitted, I’m not sure how long they will last being so small.

I have also changed the direction of the tuning needle to reflect the direction of rotation of the tuning knob by rewinding the cord around the tuning knob spindle in the opposite direction. Whilst in this area I looked around for a replacement gear wheel to drive the flywheel. A good replacement is available from Simply Bearings Ltd, it is made from Delron has 50 teeth on a 25mmPCD with a 5mm bore that needs opening out to 6mm. With 3mm thickness of packing washers behind the gear it mates perfectly with the existing gear on the flywheel spindle. The part number is DS05/50B-5.

At some point in the future I will look at the stereo lamp but at the moment I am just enjoying listening!

David

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