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REPAIRING THE PHILIPS ELC2060 VARICAP A rundown of common faults and their likely sources from an experienced serviceman. Gerry Nicholson

lthouidt this article concentrates on tuner was used in early Kreisler pushbut­ ing voltage (0 to 28 V) and band switching the Philips ELC2060 tuner, the ton sets and in later Pye and Kreisler re­ voltages to allow selection of the band re­ Aprinciples outlined apply to most ceivers, which were both Philips sets in quired. A wideband varicap tuner is not varicap tuners. While it is often difficult to disgµise, as Philips took, over both compa­ practical since it could not be produced obtain some specialized circuits and parts, nies. Some Princess portables also use this with sufficient gain to drive the IF ampli­ the Philips tuner does not present these tuner. fier, problems. The tuner in a television receiver, as in Figure 2 shows the usual methods of Some varicap tuners use in any superhetrodyne receiver, must amplify. tuning and band switching in a typical the rf stages, others such as the Matsush­ that rf signal and produce an intermediate varicap tuner. Some later tuners use pin ita ENV77405F use thick-films to accom- · frequency of suitable amplitude with a fa­ for automatic gain control leaving modate some circuitry. Unfortunately, the vourable signal-to-noise ratio. In the case the rf unattenuated. The advan­ thick-film is no longer available although of Australian 1V, the IF is 36.875 MHz. tages of this type of gain control are we have managed to duplicate it. All television tuners have automatic gain shown in a separate box. The ELC2060 tunec. was first released in control to maintain the IF output within this country in the Philips CTV model certain amplitude limits for varying IF sig- KU. Philip's first receiver (K9) had a nal strengths. '· Problem.S miniature turret tuner. The ELC2060 Varicap tuners also need a variable tun- A major source of problems in the Philips ECL2060 is dry joints where the pins are soldered to the circuit board, so the first thing to do is solder all these connections including both antenna pins. Be sure you do not cause any shorts by applying too much solder. It is a good idea to inspect your work afterwards with a magnifying glass. The next most common fault is tuning drift caused by one of the varicap diodes becoming leaky. All of these diodes are in parallel to ground with an 820k in parallel. The easiest way to check for leaky vari­ caps is to use the· highest range on your ohmmeter with a 9 V battery in series connected between pin 2 and ground. To locate the faulty varicaps lift the 22k resis­ tors one by one until the leakage disap­ pears. Use solder braid and don't apply too much heat or you may lift the thin tracks. The 22k are marked with asterisks on the circuit diagram. The VHF section uses BB109G diodes, the UHF section BB105 diodes. Replace these with BB809 and BB405 devices. It is well to note that shorted varicaps also cause snowy picture or no picture, so always check for leaky varicaps before you waste time investigating other parts. The ECL2060 uses a BF200 as the VHF gain-controlled rf and a BF180 as the UHF rf amplifier. Lightning and other electrical interference can destroy both or either of these devices. If you .... 78 - ETI March 1987