Can too much screen voltage blow HOT?

srarcade80

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I was working on a older 19" K7000 last night (model with white knobs on flyback, 1986), just capped it, cleaned it, had everything looking awesome, dropped it in a cab and its got that tinted glass crap, so i decided to turn up the screen voltage just a teeny tiny bit to get the brightness to pop that extra bit. Plugged it in and Zzzeerrppppp! No more pretty monitor. I'm done with tinted glass btw.

So I've been trying to think where I went wrong here, my guess is that last touch of the screen voltage pot put it over the threshold of life it had left? Do HOTs get weaker over time? Luckily I had already ordered a batch last week that should be here soon.
 
model with white knobs on flyback

This.

Your flyback went. These things usually fail by arcing around the screen and focus pots. Adjusting it probably jostled something, and it blew. It would have gone soon enough anyway though. The white knob flybacks are notorious enough for failing, that most of us just replace them regardless. It'll either fail like it did to you, or the focus voltage will drift all over the place as it warms up, or something.

-Ian
 
Thanks, I was afraid of this. I have known those white knob ones to be faulty but I see the HOTs go so many more times before the flybacks so I just took assumption. I have spares to try, i'll yank it out today and swap one in.
 
For some reason these flybacks just break down around those controls. I've also known people to get zapped pretty good adjusting one, as it arced through the cracked plastic housing when adjusting the controls.

-Ian
 
For some reason these flybacks just break down around those controls. I've also known people to get zapped pretty good adjusting one, as it arced through the cracked plastic housing when adjusting the controls.

Wow scary stuff! I've never been zapped yet, i'm usually really careful about these. This particular model I was adjusting while it was off because of how fragile it was. I replaced the flyback with one off a newer model, definitely fixed the problem. Although I'm seeing some really weird short white horz line appear for a second and disappear every 10 seconds or so, i wonder if this one is on its way out too. I guess I'll use it til it blows. Also it made a bit of a buzz when i tried to adjust the brightness so I left it alone, this things a house of cards I think at this point in time.
 
This.

Your flyback went. These things usually fail by arcing around the screen and focus pots. Adjusting it probably jostled something, and it blew. It would have gone soon enough anyway though. The white knob flybacks are notorious enough for failing, that most of us just replace them regardless. It'll either fail like it did to you, or the focus voltage will drift all over the place as it warms up, or something.

-Ian

hey just wondering if this is true with all the k7000 family. i have a 7901 that has what you descibe as voltage drift as it warms up. is my flyback going bad?
 
this is why it pays to just replace a fly when you have th chassis out. Its cheap insurance it really is.

i guarantee youll find some cracks when you look at it to change it

could have been just ont he edge of puking, you recap it and its supplied more juice than its seen in over 10 years, boomers...

Now, you need to hope when the fly went that there arent more issues.. give the k7000 sticky a read when you get some time.
 
hey just wondering if this is true with all the k7000 family. i have a 7901 that has what you descibe as voltage drift as it warms up. is my flyback going bad?

is the focus or brightness changing with monitor run time? if so could be... coule also be a tube etc etc its hard to tell. Lukily flys arent muh money so if you suspect it jam one in and see what you get.

to the OP if your getting some arcing sounds, make sure the anode wire is secured int he tube properly, and make sure the crt ground and focus wires are also secure...


your random line issues could be poor solder at r101 and in that area. If you can tap the chassis and make this lines issue come and go, you have cold solder joints soemwhere...
 
to the OP if your getting some arcing sounds, make sure the anode wire is secured int he tube properly, and make sure the crt ground and focus wires are also secure...

No arcing sounds from flyback. Unit visually inspected pretty good. Yep, i always make sure to visually confirm that both prongs on the annode cap get into the annode before starting. Also, with ground being most important thats my #1 checklist item.

I let the game sit on about 4 hours yesterday, still looking good, the little quirks have started to go away. I did have the screen cut out on me for a good second last night but I have a golf game in and I was spinning the trackball pretty good when it happened, so maybe it knocked something loose.
 
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