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Technical Info and Restoration Tips On Radios
THE BUSH DAC90After replacing all the cylindrical wax capacitors the next thing I do is connect the mains switch to the mains dropper part of the radio rather than the chassis, this makes it miles safer. If the CCH35 needs replacing then an ECH35 will do. If you need to replace the mains dropper then beware of the Asbestos. If the IF has no response then you may find that the coil slugs have broken.
THE BUSH DAC90A, DAC10These radios are fairly straight forward to repair, all the cylindrical wax capacitors must be replaced, especially the mains filter capacitor. If the mains dropper has burnt out then the dropper from the Ambassador Coronet which is about the same age will fit straight in. If the output valve needs replacing I always replace it with a MAZDA 10P13, but sometimes hum in the output valve can be cured by cutting the unused pin. On the DAC90A it is important that the rubber wires connecting the light bulbs and the speaker are replaced because otherwise there is a risk of speaker grille becoming live. On DAC90A radios that I sell I connect an earthed cable straight to the radio, the neutral wire goes to the end nearest to chassis and the earth wire is connected to the speaker grille.
THE MURPHY A30C, A30If the mains transformer is smoking from the top or bottom then an easy bodge will get it going again. These transformers are of the split bobbin type, the top and bottom bobbins are identical. Once you have ascertained which bobbin is faulty then the transformer must be dismantled and the bobbin removed. The burnt HT winding must be removed from the faulty bobbin. Check the appearance of the heater winding, if it is ok then put the bobbin back and reassemble the transformer. The two halves of the rectifier must be connected in parallel and the value of the smoothing capacitor must be doubled. Because of the mains energised speaker the extra hum is not noticeable and the radio works as normal.
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