Sony help...

[freakaftr8]

Hey guys, my mom gave me her tv, and it's dead. It's a 27" Trinitron dated Sep 1994. It's totally dead. When you plug it in, no clicks, no lights, no flashing standby, I did however notice the plug gets warm. Seeing this I thought the problem is in the voltage regulation circuit before it gets ho HV. Anyone ever had this issue or should I just pitch it. It did produce a great picture before it quit.

Thanks

[radiotvnut]

The horizontal output transistor is probably shorted due to loose connections on the horizontal drive transformer. The shorted HOT probably took out the two regulator transistors mounted on heatsinks and the little white fusible resistor, all located in the power supply. I think www.electronixonline.com has the repair kits for these sets.

[freakaftr8]

cool thanks!! Ill check into this, I had a hunch something like this went south...

[kx250rider]

Also see this thread:

http://www.audiokarma.org/forums/sho...d.php?t=147506

Yours, being '94, could be the next newer chassis. What's the model? If it's a KV-27TS29, or any KV-27Sxx, it should have the same board basically. What bothers me is that the plug should NOT get warm!!! I hope nobody before you went in there and disabled a fuse, or anything. Also watch for a shorted degaussing circuit. If in doubt, unplug the degaussing coil from the board.

Charles

[radiotvnut]

And, I have seen a shorted degaussing coil on an old "no name" set and again on a newer Philips. I've also seen my share of TV's with foil wrapped around the fuse. I've seen several Sony's with loose connections on the degaussing thermistor. It won't kill the set; but, it will render the degaussing circuit inoperative.

[Jeffhs]

Originally Posted by radiotvnut

I've also seen my share of TV's with foil wrapped around the fuse.

Hmmm. I wonder how many house fires have been started by faulty TVs, radios, etc. in which the AC line fuses or circuit breakers were bypassed by foolish users. This was very common years ago, when houses had electric service panels with screw-in fuses rather than circuit breakers; when a fuse would blow and a replacement was not readily available, the homeowner would simply put a copper penny behind the open fuse, then screw the fuse back into the box. This may have restored the circuit and got the lights/outlets/appliances going again, but since there was no fuse in the fusebox (the penny effectively bypassed the open fuse), the circuit the fuse was supposed to protect was put at immediate risk of being dangerously overloaded. This often led to house fires which started behind walls, when the insulation would burn off the overloaded wiring.

Today's electric service panels, in which incorruptible circuit breakers rather than fuses are used, have all but completely eliminated the fire hazard I mentioned above. When a circuit breaker flips "off" due to an overload, there is no way to bypass it as the breaker's terminals are hidden deep inside the box; the only thing a homeowner can do is flip the breaker back to "on", after unplugging the defective appliance or correcting any overload condition, of course.

[kx250rider]

I've seen TVs where the entire AC cord had glowed red, and melted off all the insulation 'til the wires touched and blew the house breaker. RCA color tube sets were famous for broken circuit breakers, and uncaring technicians would slap a who-knows-how-heavy pigtail fuse across the breaker.

As far as house fires caused by TVs, yes plenty . However, most that happened in my time were by early Zenith and Sylvania solid state sets of the 70s with ECG-500-ish triplers. When those fail, they throw out a flame like a blowtorch, so heaven help you if the TV is a plastic or wood cabinet. When those flame-ups happened, it didn't seem to draw too much current to trip a breaker or blow a fuse. The other big fire-starters were CTC-15 & 16s with bad on-off switches. They would fail when the TV was OFF, in the middle of the night or when the owner might not be home. There may even have been a recall on those, and I replaced plenty of switches that had burst into flames, usually just burning wires. However, I personally saw two of them which had flared up, burning all of the wiring on the tuner chassis, and catching the plastic channel wheel which in turn burnt a hole in the top of the cabinet.

Charles

[freakaftr8]

Ouch, wow! No the fuse in this set is fortunantly still there.. But the plug prongs get warm after having it plugged in for a minute of diagnosing.. Strange...

[radiotvnut]

I've actually seen a couple of those Zenith triplers spew fire. One was on a 17" portable that I bought at a church sell for a $1. They wanted more but after plugging it in and it "performed", I was able to get it for $1. The other one was on a 23" console that someone gave me and I fixed it for our family TV. Luckily, neither set was left on long enough to really cause a problem.

[freakaftr8]

Well I repaired the set and I did a bonehead thiing... I blew up the c4927 HOT again, due to a bad connection on the board, I knew it was whacky and the right side would start to cave in and I would have to tap the board to straighten it out. Well it was on and I researching where the bad connectuion was and the doorbell rang, I went to go answer it and I heard a pop after a few minutes, I went back in the room and the set had a flashing standby, good audio, no pic. I heard a high pitch whine as well and the HOT was cooking hot. I since repaired the connections but does anyone have a C4927 horiz transistor? I would like to purchase 2 of them. Thanks!

[kx250rider]

I hate it when the doorbell (or phone) does that ... Not to be negative, but did you recheck the 2SC4834s and the R607 too see if they got blasted?

The HOT isn't too expensive, and I might have one lying around. PM me if you dont' get one locally up there, and I'll see what I can do. If Sandy's Electronics is still there in Reno, they might be able to mail one quicker than from down here in LA.

Charles

[freakaftr8]

Sandy's electronics? Never heard of them, thats cool Reno is right around the corner from me! R607 is still good and Im assuming the 2 4834s are ok too considering im getting b+ and HV. Just standby and no shutdown protection yet, I didn't give the set long enough chance to wipe out the 4834's I believe.

Originally Posted by kx250rider

I hate it when the doorbell (or phone) does that ... Not to be negative, but did you recheck the 2SC4834s and the R607 too see if they got blasted?

The HOT isn't too expensive, and I might have one lying around. PM me if you dont' get one locally up there, and I'll see what I can do. If Sandy's Electronics is still there in Reno, they might be able to mail one quicker than from down here in LA.

Charles

[freakaftr8]

Well Sandy's does not carry them.. Hey Kx250rider, if you have one i'll buy it off you and shipping too.

[kx250rider]

Originally Posted by freakaftr8

Well Sandy's does not carry them.. Hey Kx250rider, if you have one i'll buy it off you and shipping too.

Unfortunately, and to my surprise, I don't have one . I thought I did, but I went in the Sony box and have plenty of the 2SC4834s, and the original R607s, but no HOTs. I can get one from my friend in West LA on Monday, but that means you wouldn't get it 'til Wednesday or Thursday. If you want, eMail me by Monday morning and I'll grab one.

I'm surprised that Sandy's doesn't have it... That's a generic number 2SC4927, or "c4927". They probably do have an NTE replacement, but those NTEs and the SKs are very questionable in Sonys. It's been years since I dealt with Sandy's down here in LA. The manager, if he's still the same, is Wayne Willis. He's from the store down here, and I stop in the Reno store each summer when I go up there. Always helpful when I needed a weird semiconductor or cap.

Charles
[email protected]

[freakaftr8]

Well, l replaced the HOT, still nothing. The r607 is still good, but the set will power up, gets HV, but stays in standby. If I blew up one or both of the 2SC4834's would the set still power up? I got no way to test transistors..