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The date TVs became more reliable?

 
irob2345
(@irob2345)
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Was the elimination of the paper capacitor the biggest reliability improvement to TV and electronics in general?

By 1964 they were just about all gone from Oz-made goods - with a few notable exceptions.

Polyester

These particular caps were instantly recognisable in a chassis, being light blue. As with Philips "Mustards" I don't think I ever needed to change one.

The word "NEW" is supposed to be the best attention grabber in advertising!

How quickly did paper caps disappear from UK production?

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Topic starter Posted : 05/03/2021 12:29 am
Nuvistor
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@irob2345
I think paper ones had more or less gone by the middle 1960’s in the UK, may have been the odd one about. We then had the mixed dielectric type in many locations, perhaps better than just paper but still a failure point especially in pulse circuits. 
Transistors in the signal circuits produced a big improvement in reliability, of course then were introduced around 1965/66 with valves in the power stages.

Frank

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Posted : 05/03/2021 4:14 am
Till Eulenspiegel
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For us in the UK the introduction of 625 line only TV receivers reduced the service engineers workload.  I didn't find the old 405 only sets too bad as long as one didn't come across some butchered up horror that had been through the hands of some local genius. Us older engineers will remember there was always an "engineer" about whom it was said: "if he can't fix it no one can". So I fixed the set and most cases the owner was grateful that the set had been saved but there was the occasional customer who wasn't happy at all, almost hostile. How have you repaired my TV set when my man couldn't?

Till Eulenspiegel.

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Posted : 05/03/2021 8:12 pm
Katie Bush
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Posted by: @till

but there was the occasional customer who wasn't happy at all, almost hostile. How have you repaired my TV set when my man couldn't?

We had a guy at the far end of of out street who would take on things he thought he could fix, but in reality, could not. He was the one everybody turned to when all else failed - TV, radio, vacuum cleaners, electric fires, food mixers, 'Teasmade' and you name it. In reality, it was true, "If he couldn't fix it, then no one else would" - because he did so much damage. So it surprised a few people when Alec, from a few doors down, began to tackle some of "Clever Bugger's" handiwork. That earned Alec a bit of admiration from my granddad, and a place at the bench in his later days. Alec was still only learning his trade, but the things he couldn't do paled into insignificance against the things he could do, and shot the side out of Clever Bugger's boat!

It did used to rile up a few people when Clever Bugger failed, and either Granddad or Alec got it sorted again. I think a lot of the hostility was because they felt embarrassed at having been taken in by an oaf. Clever Bugger might have been alright at simple jobs, and that might have got him through a good many front doors, but he was on the far side useless at the more involved jobs.

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Posted : 05/03/2021 9:25 pm
Till Eulenspiegel
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How about this mains dropper repair?

Pye P115 mains dropper (2)

Till Eulenspiegel.

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Posted : 06/03/2021 11:17 am
Katie Bush
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@till  By the look of it, not one section of the original dropper intact.   I've seen stacks of Polos, even green monsters, but usually with at least an original section or two still working.

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Posted : 06/03/2021 2:46 pm
Nuvistor
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If the original dropper wasn’t available I used the RS polo resistors with 2BA studding, 2BA nut between each section and wiring (new if required) covered with fibre glass sleeping. All available from Radio Spares.

Made a neat job, mounting in place of original.

Frank

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Posted : 06/03/2021 2:58 pm
Till Eulenspiegel
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Back in the sixties I saw a Bush TV125 in which the original mains dropper had been replaced with Radio Spares polo mint dropper sections. It was a neat job and every section had the correct value. Nothing to gain by replacing it.

Till Eulenspiegel.

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Posted : 06/03/2021 3:05 pm
Katie Bush
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Posted by: @till

Nothing to gain by replacing it.

No shame in it either. Also very handy if you building or experimenting with a project, and very neat if properly bolted together and attached to a suitable supporting structure.

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Posted : 06/03/2021 3:19 pm
Lloyd
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That dropper looks almost as bad as the one in my Philips 385u! The bodges are actually mine, so I can’t complain about it... I’d love to replace it with RS Polo’s, but I haven’t been able to get the correct values.

As for when tv’s became more reliable I think it was late 70’s early 80’s, lots of 80’s TV’s turn up fully working without ever having the back off, our Toshiba only had one service call in it’s 20 years service, and that was just dry joints causing intermittent line collapse, the set itself is still going strong in my workshop! Purchased new in 1987!

Regards,

 Lloyd

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Posted : 06/03/2021 3:20 pm
Till Eulenspiegel
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The mains dropper was replaced by using a type of 7 watt  resistor that was in common use in the seventies. The three sections in the Pye P115 mains dropper are R17 the 180 ohm anode resistor of the UY41 rectifier and R18 and R19 the series heater chain dropper resistors. R18 was 930 ohms, now replaced by two of 1.8Kohms and R19 was 300 ohms and replaced by a 330ohms resistor. R18 and 19 together dissipate 12.3watts. I suppose a 1.5microfarad capacitor would be a greener alternative but I didn't have a class X capacitor at the time the set was being repaired.

Pye P115 mains dropper 2

 Till Eulenspiegel.

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Posted : 06/03/2021 7:02 pm
sideband
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Posted by: @lloyd

That dropper looks almost as bad as the one in my Philips 385u! The bodges are actually mine, so I can’t complain about it... I’d love to replace it with RS Polo’s, but I haven’t been able to get the correct values.

That is one reason why I now consider a capacitive dropper. Much neater than trying to cobble together wirewounds to make up the value.

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Posted : 06/03/2021 9:33 pm
Till Eulenspiegel
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The model 2 Pilot Little Maestros I have here have been fitted with a 4 microfarad capacitor which is used as the replacement for the resistive line cord.  The valves employed in this set are 0.3amp heater types, 6K8G, 6K7G, 6Q7G, 25L6G and 25Z6G. The total heater chain voltage is only 70 volts.  That's 170 volts to get rid of and a resistive dropper will dissipate 51watts! Anyway, there's no space inside the small cabinet for a dropper resistor or transformer.  Later Little Maestros were equipped with 0.15amp heater valves, the 12K8 series.

Till Eulenspiegel.

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Posted : 06/03/2021 10:15 pm
irob2345
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I feel so fortunate that we in Oz had to deal with none of that. Service techs had enough clout with the retailers that radios and TVs lacking an isolating mains transformer would not be sold. Very few exceptions.

Because of this there was some volume in transformer manufacture and set makers learned how to make or specify good, cheap transformers and sets ran relatively cool, as they had to do in our climate.

There was an egregious exception - an early Sharp CTV chassis was designed to run on 100 volts and so there was a HUGE 150 watt dropper resistor on a metal bracket, screwed to the inside of the cabinet. This chassis had a very short production run!

Same thing happened with easily steal-able cars. The major motoring insurer (NRMA) came up with a ratings system so that if your car was hard to steal, the insurance premium was much lower. Manufacturers changed things VERY quickly!

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Topic starter Posted : 07/03/2021 9:41 am