Catastrophic Flyback Failure

[Jdurg]

If only I had a video of this to show you guys.  WOW!  I had finally gotten my monitor adjusted properly, and had recently replaced the full set of capacitors, including the B+ Filter Cap, the HOT, and the flyback.  (Thanks Ian for the cap-kit.  Was super easy to install).  Everything went on incredibly easily and the image looked amazing.  No cold solder joints, no shorts, no nothing.

Today, i was finishing up adjustments when my hand accidentally hit the yoke of the tube sending quite a bit of electricity into my right arm.  Felt like I was stabbed and punched VERY hard at the same time in the same spot.  Heh.  They aren't kidding when they say that a CRT can REALLY hurt.  Glad I followed the advice of everyone and always kept one hand in my pocket while adjusting the width coil to prevent a charge across my heart.

Anyway, while finishing up the width coil adjustment, i noticed that the neckboard wasn't seated fully against the neck of the CRT.  You could see about a mm of pins all around the tube.  This was likely from when I was first moving the tube and it slipped, causing it to lean onto the neck connector.  I straightened out all the pins, but i guess I didn't straighten out the key plug enough.  So i went and got that sorted out and had the neckboard fully onto the CRT tube.  No pins showing.

As i've generally been doing, i turned the setup on and let my game play through it.  This keeps everything warmed up, and is nice background noise for me. 

While I'm sitting in the next room, i suddenly hear this loud screeching noise that was kind of like a record being scratched.  I quickly jump up from my seat and run over to the room to see no picture on the screen and a TON of bright white arcs in the back area of the monitor.  I nearly trip over my feet running for the power plug to unplug this thing.  The smell of ozone filled the house.

After my nerves calmed down and I flooded the shout box here with my tales of woe, I went over to the tube, discharged it, removed the chassis, and closely inspected the CRT.  Thankfully, it appears as though the vacuum is still present as the getter inside the neck is still a nice shiny silver color.  I then looked over the board and saw no signs of physical damage.  No funky looking capacitors, no charred parts, no overheated solder joints.  It all looked good.

I then pulled out my multimeter and checked the HOT in circuit.  Got readings of 0.490 on each leg so it appears as though the HOT was not damaged in any way by this failure.  I'll test it out of circuit tomorrow as I'll need to remove it from the board per the problem I did see.

It looks like the flyback i had replaced was a dud.  The ferrite cores that meet in the middle of the flyback itself and have a wire C-Clamp holding them together on the outside is INCREDIBLY loose. With the flyback on the board, it readily swirls around in all directions.  i'm guessing the arcing I saw was coming from this.  The flyback was manufactured earlier this year, but I guess something finally came loose and resulted in the catastrophic failure I witnessed.

Going to try to head to bed right now and sleep this off.  Will do some extensive multi-meter testing tomorrow and will remove the flyback and toss it in the trash.  I'm hoping that a new flyback on here will be a good one and won't result in an insane light show and soiled pants.

[iankellogg]

You are lucky this flyback is not known to cause catastrophic damage to the rest of the board.

Now this is a great time for me to say this. NEVER replace a flyback that isn't bad. You are not doing yourself any favors. the new ones aren't any more reliable and in many cases are less reliable. You should only replace a flyback when it is Bad or if its one of the few flybacks that are known to have very high failure rates.

[Jdurg]

Well I had a feeling that the flyback that was on there was starting to fail on me anyway.  It was crackling/buzzing quite a bit, and when I replaced it that buzzing went away.  So it was only going to be a matter of time before it went out on me.  i know that there is an instrument that can fully test a flyback, but there is a test that can be done with a multimeter to check the capacitance between the anode cap and ground.  i get nothing from that when i measure which means that the capacitor in the new flyback is shot.  That would explain the failure.  Oh well.  Lesson learned.

[iankellogg]

There is no capacitor in a flyback. It is extremely difficult to test a flyback without actually running it. The lowest voltage I have seen for a monitor flyback is 8Kv. it is pretty tough to even find an insulator tester that can even go to 8Kv. The K7000 I believe runs at 27Kv, I don't recall exactly. Unless there is a super awful failure you wouldn't be able to ever test a failed flyback.


I will say that you still did the right thing replacing the flyback the first time, it was clear that one was on its way out. But this is more of a general comment for others. Do not replace a flyback that isn't failing. You are not buying yourself ANYTHING.

[Jdurg]

Okay, thanks.    Regardless, I have learned a LOT about monitors and their repair, etc.  In the meantime, my blank eproms came in the mail today so I am programming the version upgrade for my SF2:CE board, as well as the hyperfighting ROM upgrade.  So at least I have something to do.  Hopefully my flyback gets here early next week and i can test everything out again.

Thanks again for all your help.  The cap kit is great, and although the previous owner of the chassis said that he had done a cap kit, I did notice some subtle improvement in the image quality once i had done mine.   

[Jdurg]

Wanted to post an update here in this thread.  As stated previously, the flyback on my chassis went up in a blaze of glory.  Bright blue/white sparks, a horrific noise, and a really scared Jdurg.

I ordered the flyback and it supposedly had arrived this past Tuesday, but unfortunately the shipper erroneously left the flyback out of the box and had to quickly ship it to me.  (Must say, the response from Twisted Quarter was fantastic, and very courteous.  Andrew profusely apologized and got me my flyback only a few days later).

So I got the flyback in and hooked it all up.  Turned it on, and the only thing I saw was blue/white beams arcing in the neck.  My worst fears turned out true.  The vacuum was gone.  I quickly turned it off and disconnected everything.  Upon closer inspection, I saw this:



A small crack up near the top by the neckboard connector.  The tube is officially a very heavy pile of semi-toxic waste.  heh.  I'm guessing that the neck cracked a small bit during one of two instances.  One was early on when I was taking the tube out of the TV case and it leaned down fairly heavy on the neck connector.  The only damage I noticed at the time was some bent pins, and minor deformation of the connecting socket.  Still, I put the neckboard on after that and the tube fired up and worked great.  So I did not suspect anything.  The second possibility was when i decided (For some stupid reason related to my OCD on perfection) to "un-deform" the connector.  i was able to do this and got the neckboard on after a sudden jolt.  Again, however, I powered it on and had a beautiful picture for about an hour.  That's when the flyback blew.

I figure that when the flyback blew, the sudden increase in temperature caused by the high voltage discharge in the area created a little thermal shock to the glass in the neck.  The tiny crack that had existed before, but wasn't full distance through the glass, then fully opened.  When it blew, i heard a very loud and violent sounding screeching/scratching.  I guess that was a combination of the electrical discharges, the speakers picking up that discharge in the air and making a horrible sound, and air rushing into the tube.

I did order a new tube to put in there (And hope to get confirmaiton that it will be delivered this coming Monday as the company did confirm my order), so I will just hope that the tube comes with the yoke and purity/convergence ring assembly so that I won't have to go through that experience.  Heh.  But a sad end to my first ever experience with arcade monitors, but you know what?  The tube was free and no matter how careful and experienced you are, a cracked neck may eventually happen to you.  I just got mine out of the way the first time through.   

[John's Arcade]

Wow, crazy story. Sorry to hear you got shocked. It sucks. CAREFUL OUT THERE!

[Jdurg]

Thanks John.  It's a learning experience.  I figure if someone works with CRT monitors enough, they'll get bit once and they'll also have a neck crack.  I just got mine out of the way early.   

[oscar-hernandez1983]

I'm fixing to discharge a monitor for the first time I'm scared so any advice of what to do and what not to do.I've been watching videos on how to do it and getting shocked it's something not very pleasant.

[Jdurg]

No real need to be scared.  As you heard from my story, I only got a bit of a bite when mucking around with the thing on.  Not from discharging the monitor.  In the one monitor chassis I've worked two tubes on, there was never any issue with the discharge.  My chassis board must have a bleed off circuit as I have never even heard the tiniest crackle, let alone see a spark, when discharging it.  I've now discharged this thing dozens of times. 

It really is as simple as it seems.  It's just that the built in fear of getting "bit" makes it seem much more complex.

If you watch a bunch of videos on YouTube with people discharging a monitor, and you soon start to know what they're going to do next and aren't surprised, then you know all you need to know.

Also, just for peace of mind keep your other hand in your pocket.  This way it doesn't get in the way or get into things it shouldn't touch. 

[iankellogg]

K7000 is self discharging. Older monitors are not and will produce a snap when discharged. The first time is always the scariest but it really isn't that bad. just don't stick your fingers in the tube's hole. dont touch the metal prongs with your fingers when removing the anode cup.

Don't touch the back of the neck socket when its powered on. In general don't probe the monitor with anything while its powered on. if you must probe something, hook it up with the power off and then turn power on.

[oscar-hernandez1983]

Thanks guys I feel more confident to do that today. I've got some industrial rube gloves just in case my wife is more scared than I am now but we'll see how it goes.