Sony CRT TV. Audio OK. If the set is turned on all is normal for a minute or so. Then the picture is gone and screen fills with uniform illumination plus about 20 or so fine horizontal lines slightly tilted up on the right. After a few more seconds the screen gradually gets very bright white and, wham, the set clicks off by itself. If I turn the set on again it repeats. Anyone have a clue as to what is wrong?
Alex
Model is ???
Model is Sony Triniton KV-32HSR10, purchased new 2 Dec 1991.
right.
and,
Sounds like a HV regulation problem, HV is increasing until the Xray protection kicks it off. Could be as simple as a solder joint or a capacitor.
look around the line transformer area for bad soldering, and change the rgb filter capacitor (usualy rated 250 v 10uF or so, often on the crt neckboard)
-B.
Focus leaking to G2, overloading the horizontal section?
Tom
minute
illumination
repeats.
11/5/2005 Thank you all for your replies which I will certainly take into consideration when I attempt to do repairs. This will be the third time I have had to repair this TV. The first time (about 10 years ago) the set behaved erratically when subject to vibration. After much poking around (with a long plastic rod) I found out that some components on the circuit boards were loose. Amost all of the small voltage regulators (about half the size of small postage stamps) were loose so I resoldered all I could find and that fixed it. The second time I could not locate the problem but resoldered all the solder joints (which looked very good) on the HV transformer board and by pure luck that fixed it. This third time may be more challenging! I will keep you informed but it will take some time - maybe a few weeks because of other duties.Alex
right.
and,
but
A HAPPY EVENT! This Saturday evening I opened up the TV and removed one of the circuit boards for inspection and resoldered some suspicious looking solder joints. Then I replaced it and turned on the set and nothing changed - set still did not work. Then I turned on the TV and pushed down on the HV transformer with a long stick so as to distort the circuit board it is on and WHALA that did the trick. The set now works fine!!! I guess I will have to resolder components on this board sometime soon since I suppose there must be a loose solder joint somewhere. I do not understand why this Sony TV has had so many defective solder joints. It is a wonder that it has worked at all over these many years.
Alex
"amcwill417" bravely wrote to "All" (05 Nov 05 22:59:36) --- on the heady topic of "Re: Problem for 15 year old 32" TV"
am> From: "amcwill417" am> Xref: core-easynews sci.electronics.repair:347676
am> A HAPPY EVENT! am> This Saturday evening I opened up the TV and removed one of the am> circuit boards for inspection and resoldered some suspicious looking am> solder joints. Then I replaced it and turned on the set and nothing am> changed - set still did not work. Then I turned on the TV and pushed am> down on the HV transformer with a long stick so as to distort the am> circuit board it is on and WHALA that did the trick. The set now works am> fine!!! I guess I will have to resolder components on this board am> sometime soon since I suppose there must be a loose solder joint am> somewhere. I do not understand why this Sony TV has had so many am> defective solder joints. It is a wonder that it has worked at all am> over these many years.
Alex,
Heat around power devices will cause thermal expansion and then contraction when cooled. Eventually the solder becomes metal fatigued and brittle. This increases resistivity of the solder and the joint can even burn up in extreme cases.
Case in point, when replacing power transistors in audio amplifiers I always used to leave a little semi-circular bend to the leads so that as the devices heated up the bend would take up the slack and wouldn't pull when cooled again.
A*s*i*m*o*v
... Wasted power is current squared times the resistance.
works
A good practice. Based on my several experiences with this television may I put forward a first rule for repair: First bang (somewhat gently) everything you have access to - like kicking the tires of an older car. If the trouble goes away even temporarily then suspect a loose connection somewhere. For TVs or other devices with high voltages use a long insulated rod, say a 3 foot long dry plastic rod, for safety.
Alex
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