Dead Sony KV-T25SZ8 TV

This brings us back to the Sony problem. On many sets you can use standard transistors and other semiconductors, at least for test purposes, so it is usually worth a punt for a few quid to see if it fixes the set. But an expensive chain failure which necessitates the use of genuine parts (a typical sony scenario!) means that these sets are not often worth bothering with. In this case I had no idea of the set's history, for all I know the tube could have been wasted too - another reason not to put serious time and money into such an item.

It is ironic that latterday CRT 'supermarket sets' tend to have a better chance of getting fixed than some of those costing several times as much!

-B

Reply to
b
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From memory, and I may be wrong - It was not protected by the fuse, only by the blown PCB tracks. (and there was current limiting from there being a relatively thin wire leading from the battery + to this part of the circuit.)

The circuit was not easy to trace out, and parts like this seemed illogical.

The thing that probably killed it was that I was using it to charge up about 5 SLA batteries, one after the other, and it might not have been designed to be charging for this length of time continuously. once the

5th battery was connected - smoke time.
Reply to
kreed

Still, I'd have expected it to have reached thermal equilibrium long before even the first battery was fully charged. It shouldn't get any hotter from subsequent chargings.

Sylvia.

Reply to
Sylvia Else

The set's inability to show any signs of working circuits, with the HOT (transistor) removed (or failed), is normal for most TVs made within about the last 25 years.

Other than a Standby voltage supply, most TVs won't operate (even partially) without a functioning horiz scan/sweep circuit, as in general, several voltage supplies are derived from the IHVT integrated high voltage transformer (some refer to as flyback or other terms).

-- Cheers, WB .............

Reply to
Wild_Bill

My Sony KV-1920, purchased ca. 1974, was one of the first TVs with a switching power supply. When the supply failed in the early 80s, a guy from Sony warned me not to try to fix it myself. "If you don't catch all the bad parts the first time, some of the replacement parts might fail. It's best to have a trained tech look at it." It cost me around $75 (which seemed a lot, then) but the set was properly repaired and worked another 15 years.

Reply to
William Sommerwerck

You are probably right, but this was the only change to "normal" usage I can think of before it failed

Reply to
kreed

On a hunch, I checked the garbage AOL email addy that I use to register for public forums, and there (amongst the ton of spam emails) were more than a couple of emails offering the same advice. But I'm not completely convinced he has mood swings or a personality disorder; I suspect he's a typical internet bully who can only demonstrate bravery from behind the security of a keyboard. If someone were to act like that in real life, you go up to them, grab them by the throat, and watch them fill their Pampers. Still, I've often gotten a good laugh from his posts.

Reply to
Stroonz

Coincidence - there's probably a yet to be discovered perverse law of nature that says that a machine is most likely to fail shortly after a totally irrelevant change in the way it is used.

Sylvia.

Reply to
Sylvia Else

Well, that's possible, though as I've indicated, my TV wouldn't even enter standby mode.

I suppose it's conceivable that since it failed in operation, it always tries to power up in that mode, and that the processor won't allow entry to standby mode unless everything's working. That would seem a bit perverse, but who knows?

Sylvia.

Reply to
Sylvia Else

Here's another one... "A machine is most likely to irreversibly fail shortly after you've gone to a great deal of trouble to fix it."

Reply to
William Sommerwerck

In the dark old days (mid 70's) we would find that in Sydney during the months of December to March the high temp and humidity would cause triplers to fail (mostly with dust all over them) which would take out the HOT and sometimes the PSU. Consequently there were a number of brands of TV's that we would stock up on these parts in October ready for the rush. I'm not suggesting that this is your fault, however it does seem familiar.

Reply to
Swanny

These types of failures are the kinds of problems that TV techs have seen regularly for a lot of years.. a relatively simple fault is capable of causing the "smart chassis" type designs to be completely dead, in many cases.

In sets that develop a fault, and also have some other components that have changed values due to age, the chassis essentially has compound faults, which were commonly referred to as Tough Dogs, among other names. Shut-down circuits have been implemented for many years, to prevent the TV from operating at all, if the CRT's HV potential exceeded a limit, as a safety shutdown.

Some minor faults are often complicated by poor soldering during the circuit board manufacturing process/build, which creates new faults as the boards age and go thru many thermal cycles.

Many of the electronic equipment designs presently manufactured are similar designs of smart chassis design, in that one fault will disable every function.. maybe with the exception of a blinking LED. In many of these designs, either everything operates within normal limits, or the units just shut down and won't restart without experienced technical intervention.

-- Cheers, WB .............

Reply to
Wild_Bill

The term probably dates back to at least the 30s. It refers to a problem that refuses to yield to common-sense analysis or trouble-shooting.

Reply to
William Sommerwerck

I've had dialog with Phil that was very helpful and he's even apologized to me (in his own way) once. On other occasions he's tore into me for no reason whatsoever. And it's not just me but others that don't do things the Phil Allison Way. I have no official proof but this behavior smacks of a sever mental disorder.

--
Live Fast Die Young, Leave A Pretty Corpse
Reply to
Meat Plow

"William Sommerwerck" wrote in news:ilp3r9$p3i$ snipped-for-privacy@news.eternal-september.org:

It is called "the innate perversity of inanimate matter". There was an article on it published MANY years ago in CQ magzine.

It have some ways to use ipoim to do things around the ham shack.

1) in order to prevent stretching from detuning your antenna, cut the wire short to allow for stretch. 2) to fix a complex electronic device: a) go through the parts list and contact all the parts suppliers. You will find one or two parts that can not be found anywhere; it is one of those. b) examine the layout and locate the part that is most difficult to remove and replace. You just found your defective component. I don't remember the rest of the article but it has proven to be quite useful to me, over the years. :)

73 de N5bz

Reply to
bz

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