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

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.

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

Also see this thread:

http://www.audiokarma.org/forums/showthread.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

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.

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. :scratch2: 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.

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

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...

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.

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!

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

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.

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

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

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 :no: . 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
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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..

When you say the set has HV, I assume you mean to the CRT. Can you feel static on the screen when you turn it on?

Every time I've seen one or both of the 2sc4834's shorted, the set was dead and the resistor was open.

It could be that there is too much B+, triggering the shutdown circuit. I think the B+ should be 130 volts or so.

Yes there is HV, static on the screen.. Ill try to measure the b+, if it is high, what should I look for?

I've never seen high B+ on these sets. If it's high, I'd poke around the power supply board. One other thing, the standby light will blink a certain number of times when a newer Sony shuts down. The number of blinks indicates what fault is causing the problem (overcurrent shutdown, vertical sweep failure, etc).

This one's not shutting down, just continuous standby. Think I might have shorted something, I just found the black wire for the grounding of the Degausing field touching the "A" board shielding! Yipes!

And in that graceful event it seems that it might have taken out the vertical output IC, this is a 3 pole that has a heat syns that is mounted next to the plug in jungle board which I think is called the "A" board? Well the degausing coil might have unloaded onto the Vertical IC heat sync and the reason I think this is it is that thwe 6.3 ohm resistor that is in circuit with that IC gets extremely hot while the set is powered up for about 20 seconds and it's sitting in standby..

If the vertical IC failed, the set would kill the video. I haven't really found any vertical problems in those sets, so I don't have a good mental picture of it the way I do with the power supply and high voltage areas.

As RadioTVnut said, the standby light will blink a code to tell what the nature of the shutdown is. Unplug the set, wait a minute or 2, plug it back in, press power once, and count the number of blinks in each set. I don't have a manual anymore, but I think vertical collapse may be 7 blinks? DON'T count on that! It's only a faded memory.

Charles

That makes sense, I know the sony blink code, this one is not giving a code, just a continious blink, like when you power it up, the blinking and accociated HV and audio, I can even see some light in the screen with the lights off representing HV, but it will not come out of standby, and the audio and HV never go dead, it will sit there with HV and audio forever probably.

What happens if you turn up the screen control? This should over bias the CRT so that you can see something on the screen even if it's blanked. If you have a full raster, then you know it's not a vertical problem. The fast that it has HV makes me think this might be an unrelated problem. I've never seen a bad HOT do any other damage than to the power supply (which has to be working for it to have HV).

Well the resistor that gets hot is coming off the vetrical frequency IC that I believe the wire touched. This IC is a 3 pole and looks like a transistor except it uses a metal base to connect the screw to the heat sync. If I crank up the G2 I get a white raster while the set is in standby.

If it's a full raster, then the vertical isn't the issue... Be sure to set the G2 back to exactly where it was, or a little lower if in doubt. Otherwise, the video won't pop on in those sets.

Is there any display on the screen when you push the volume, and is there any sound?

One thing that sometimes gets me is that the small interconnect plugs from the CRT board to the main board can get partially pulled out, so you might double-check those. If nothing, then it might be time to troubleshoot the video circuit.

Or if you want to make the set work, you could cheat, and just get another chassis for it. I bet my friend in West LA has a dozen of those sets working, but with a dim tube.

Charles

Hmmm, that might be interesting.. You know this set really aint worth anything, but just one of those satisfied feelings that your giving a set to someone in need that you fixed. As for the video, there is no osd at all, the remote will control volume and channel as well as everything else, just no raster.
The stupid mistake I made was having the black wire that goes from the Degausing field unplugged from the crt neck board, and it touched the metal frame that goes around the big IC on the "M" board (I believe it's called) (the one that stands up from the mainboard).

That black wire from the degaussing shield to the CRT socket is the aquadag ground lead. It must be connected when the set is on. Otherwise, a charge will build up and it will arc to whatever. There's no telling what it fried. You may be better off to find a chassis out of a set with a bad CRT.

Well I give up on this POS! If anyone has a spare chassis, my set is a KV-27V10 from Sep 1994, the chassis is fried. Thanks!

Let me see if I can find one at the shop in West LA... I probably will go down there between this Thursday and next Wednesday.

Charles

Awesome, thanks charles! I would normally give up on this thing and send it on it's merry way to tv heaven, but the CRT is excellent and the case is still great

That's a good tube too A68KZJ50X... I think '94 was the first year they used that one to replace the AWFUL A68JMT50X that was in the early 27" sets.

Charles

Hey guys, just giving this thread a nudge, Charles, did you ever find out if you had a chassis for a kv-27v10?
I've about givin up on this chassis, Raster (and full with g2 turned up) but R643 gets really hot and the retrace lines are bowed in on the center of the screen about 2".



That's a good tube too A68KZJ50X... I think '94 was the first year they used that one to replace the AWFUL A68JMT50X that was in the early 27" sets.

Charles

Hey guys, just giving this thread a nudge, Charles, did you ever find out if you had a chassis for a kv-27v10?
I've about givin up on this chassis, Raster (and full with g2 turned up) but R643 gets really hot and the retrace lines are bowed in on the center of the screen about 2".

Sorry I dropped the ball on that... We had a sudden family problem come up, and I never went down to Bob's place to see if he has one. However, I'll call him today and ask him. I'm sure he does, unless he recently did a big throw-away campaign. And he owes us a favor lately because my girlfriend re-did his business software for him.

Charles

Hey guys, scrap this one... Sadly, I had this set on my bench and my dog somehow wpapped the cord around his leg, (the back was off the set) DOWN CAME THE SET AND SHATTERED THE CRT NECK! Needless to say the set is now rendered useless, the board cracked in 3 peices as well. My dog is fine, a little shaken up. Thanks for all your effort guys. Looks like ill be buying my mom a new one.




Sorry I dropped the ball on that... We had a sudden family problem come up, and I never went down to Bob's place to see if he has one. However, I'll call him today and ask him. I'm sure he does, unless he recently did a big throw-away campaign. And he owes us a favor lately because my girlfriend re-did his business software for him.

Charles

I hate that happened; but, better the set get destroyed than the dog. Save those boards. You never know what you may need one day.

So the dog is OK? I hope so... Sorry that happened. I would unsolder and save the tuner, and definitely the flyback and the HOT and the 2SC4834s. You WILL find another set like that at the curb soon, and it will be a quick fix with those parts.

Charles