Isolating heater voltage? - pics?

midcoastsurf

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Thanks to everyone's help here, it sounds like I have an H-K short on my monitor. Does anyone have pictures showing how to isolate the heater voltage using the flyback? I have a write-up, but it would be great to see pictures of the flyback and how it is connected to the tube and neck board.

Thanks!
 
I do that all the time on "worst case/beyond hope" monitors. It can be kinda different from monitor-to-monitor.....depends on brand and model.

Basically, I take a razor blade knife and cut the heaters return trace out of the neck board at the neck socket. Be careful, sometimes other circuits are using this return as their ground. Those have to remain intact to the ground/return trace...sometimes they have to be jumpered. The other side of the heater usually has it's own wire going to the neck board. Or it goes through a resistor/coil on the neck board. Just unsolder the wire...or one side of the resistor/coil/whatever conponet is inline next to the neck socket. Grab you 20 inches or so of wire and wrap it around the ferrite arm of the flyback....3-4 wraps is usually enough. One end of the wire goes to the return you cut out and isolated....the other end of the wire goes the the other side of the heater circuit you isolated. If the monitor is still kinda dim from heavy use/screen burn....unsolder one end of your wire wrap and give it another wrap around the ferrite. Done...home-made heater.

Edward
 
Edward, thanks for your post! There is one thick, black wire going to the neck board on my monitor and plugs into a single male header pin right below where the neck board plugs into the tube. Is this the heater return wire?
 
Edward, thanks for your post! There is one thick, black wire going to the neck board on my monitor and plugs into a single male header pin right below where the neck board plugs into the tube. Is this the heater return wire?

Nope.

The easiest way I've found to do this is find which two pins on the neckboard are the "heater pins" and cut the traces right below them, isolating them from the rest of the neckboard. Then arrange the wire as described above.
 
It sounds like one end of the wire is soldered to one heater pin on the tube and the other end, after being wrapped around the flyback core 2.5 times, is soldered to the other heater pin. If this is the case, was a molex connector used so that the chassis and neck board could be pulled away from the tube if repair was need later on?

Thanks again!
 
It's not soldered to the tube pins; it's soldered to the connector pins on the neckboard that makes contact with the tube pins.
 
There is one thick, black wire going to the neck board on my monitor and plugs into a single male header pin right below where the neck board plugs into the tube. Is this the heater return wire?

This (sounds) like your dag ground. That's pretty important to stay connected. If you're going to attempt this, you need to be really careful. There's some seriously high voltages running around the neckboard. You DON'T wanna connect wires to the wrong spot. The potential is there for major damage.

Edward
 
If I don't post back for a couple of months, you'll know it didn't go so well. I always make sure to discharge the monitor a few times, waiting 5-10 minutes between discharges, when working around the monitor. I'll take my time and be careful.

Thanks
 
If I don't post back for a couple of months, you'll know it didn't go so well. I always make sure to discharge the monitor a few times, waiting 5-10 minutes between discharges, when working around the monitor. I'll take my time and be careful.

Thanks

I'm not talking you....I'm talking about destroying the tube or chassis. :)
Say...if you go pumping the screen voltage down into the heater...

Edward
 
I tried to isolate the heater - no change - now what?

I connected one end of a piece of wire to the heater ground on the back of the neckboard, wrapped the wire around the flyback ferrite bar 2.5 times, then soldered the other end to the heater pin on the back of the neck board. I cut the heater trace and heater ground trace on the back of the neckboard. I then hooked everything back up, and there is no difference. The screen is bright red with horizontal retrace lines.

I'm guessing that somehow the heater did not get isolated?

Thanks
 
Just curious, but what all was checked before making the determination it was an H-K short ?
Are all the red control pots good ?
Pull the red drive transistor ?
 
Pull the red drive transistor, hopefully you won't have red anymore (I've noticed w/ an H-K short, lots of times it takes out the drive transistor too).

DogP
 
I connected one end of a piece of wire to the heater ground on the back of the neckboard, wrapped the wire around the flyback ferrite bar 2.5 times, then soldered the other end to the heater pin on the back of the neck board. I cut the heater trace and heater ground trace on the back of the neckboard. I then hooked everything back up, and there is no difference. The screen is bright red with horizontal retrace lines.

I'm guessing that somehow the heater did not get isolated?

Thanks

Did you make sure the traces were completely cut?
You could also have a grid short. I've had that happen twice, now.

Edward
 
I'll pull the red transistor and go from there. I'll keep ya'll posted.

Thanks again for all the help!
 
I'll pull the red transistor and go from there. I'll keep ya'll posted.

Thanks again for all the help!

If you pull the red transistor and it's still red.....you've got a grid short. Only way to get rid of that is to hit the tube with a rejuvenator and hope it burns it off.

Edward
 
I pulled the red transistor and the red disappeared. I have no green, only blue (with the red transistor removed.) It appears that my red transistor or pot could be the problem as well as the green tranistor?

I'll try swapping the blue transistor to the where the green one is and see if I get green.

Any other ideas?

Thanks
 
That is strange. The color circuits are all separate. One shouldn't affect the other.

Edward
 
I should mention that I was never able to "dial" in green. By that, I mean I could only get blue and red on the screen, but members here said that since I had white text on the screen, that I MUST be getting green since all three colors are needed to make white. Currently, I am only getting blue and red. No green and no white. The text is in blue. I have tried adjusting all color pots and the red and blue drive pots to no avail.
 
I pulled the blue transistor and swapped it with the green transistor. While they were off the board, I tested them and they both tested the same. If I turn the "green" knob on the neck board there is no difference on the monitor. The monitor is mainly blue/light blue now, but if I turn up the "red" on the neck board the monitor goes red. If i turn down the blue knob on the neckboard, the monitor goes black.

Any more ideas?

Thanks
 
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