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Serviceman's Log

When is it time to retire an ageing TV set? Most people are only too happy to scrap a faulty set and go and buy the latest technology. Then there are those who are too devoted to their existing set to see it go - especially if they paid a lot of money for it.

by the TV Serviceman

Loewe sets can be a problem when it comes to quoting. Invariably, their owners have parted with a motsa for what is undeniably a very good set and that’s where psychology comes in. The implication is that because they have spent top dollar, they have bought the very best and therefore it is not likely to break down. Or if it does, it won’t be serious (or so they think).

Unfortunately, in reality, there is very little correlation between buying a complex high-tech set and reliability. In fact, you could argue that there is more to go wrong in a complex set.

Items Covered This Month

  • Loewe Concept 7000 TV set (C9003/93 chassis)

  • Grundig Xentia 72 Digi100 M72-420/8/Dolby TV set (CUC1038 chassis).

  • Philips 43PP925/79 CRT rear projection TV set (A10PTV2.0 chassis).

  • Anyway, a neighbour brought in his Loewe Concept 7000 which was dead. And for some reason (possibly to do with the foregoing), he was under the strong impression that it was either a fuse or a small adjustment and that it would cost very little to fix.

    I plugged it in and the red standby LED immediately came on. Then, when I switched it on, I could momentarily hear a hiss as the EHT came up, after which the set reverted to standby mode.

    My next drama was identifying which chassis this was. Its "Art No." was 52431 and it said it was a 110C93. Eventually, I determined that it was a 1993 C9003/93 chassis, which made the set 14 years old.

    Despite its age, the cabinet looked to be in mint condition. However, when I removed the back, I discovered that the chassis was badly corroded (it’s amazing what seaside salt-air does to electronic equipment). That by itself should also have condemned the set.

    In view of this, I told my neighbour that I thought the set wasn’t worth fixing. Even if I fixed the current problem, it would probably fail again within a very short time for other reasons.

    Unfortunately, he just kept looking at the smart front of the set while murmuring something about Loewe being the "Tiger Tank of German TVs". In short, he wanted it fixed and I couldn’t persuade him that it really wasn’t worth it.

    In the end, I gave in and got on with it. First, I removed the chassis and checked for dry joints and for signs of overheating. That done, I cleaned the chassis and left a film of CRC 2-26 all over it to help protect against further corrosion.

    Click for larger image

    Because the EHT had initially come up, I suspected that the protection circuit had been activated by a faulty vertical output IC (I561). This IC is – or rather was – a TDA8175 which can be difficult to obtain these days. However, you can substitute a TDA8172 and change 10 other components around it.

    Fortunately, I managed to get one of the last ones in captivity but I was disappointed to find that this didn’t completely fix the fault symptom. Instead, the set was now coming on with sound and a very dull picture before cutting off again. When I first tried it, it cut off very rapidly but over time, it began taking longer and longer.

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