Wells K7400 Flyback

[itsdarkout]

Ok, so I changed out my flyback on my K7400 monitor. The flyback is the correct one. When I fired up the monitor, I'm not getting any picture at all. The tube is lighting up, and there's "static electricity" on the screen, if I touch it. It powers up normal, and shuts down normal. I'm just not getting any picture at all.

Any ideas?

Thanks,
Todd

[itsdarkout]

oh, and the monitor was working before I changed out the flyback.

[Kevin Mullins]

Well why did you change the flyback then ?

Did you plug the video signal cable back in?

[itsdarkout]

it was on its "last leg".

[Ken Layton]

Let's go through a checklist to be sure everything was done:

New flyback gets soldered to main circuit board. All pins soldered? Soldered nice and neat?

Screen voltage wire (the thinnest wire on the new flyback) connected to the correct terminal on the neckboard?

Focus voltage wire (next thicker wire on the new flyback) soldered to the focus terminal of the CRT socket on the neckboard?

High voltage (large thick red wire with suction cup) connected to the picture tube?

Ground (black) wires reconnected to neckboard?

Main board reinstalled and bolted down to monitor frame?

"Screen" control on flyback adjusted?

"Focus" control on flyback adjusted?

Monitor had a capkit installed while main board was out?

Main board was inspected for bad solder joints?

Brightness and contrast controls adjusted?

With your high voltage probe, measure the high voltage as you power up the monitor. Does voltage climb real fast then drop to zero? If so you've got problems on the main board still. Does voltage read steady anywhere between 19,000 and 24,000 volts?

[itsdarkout]

not sure on the voltage probe.. I don't have one. This is the first flyback that i've replaced.. But i've done cap kits, so I can solder.

Something I also forgot to mention is, the flyback seems to be making a "electrical whinning" type noise. Its kinda scaring me a bit. LoL. If the best thing to do is take it to my friend, who can fix them, I'll do that. But I try not to bother him, cause he's really busy.  So any idea what the noise coming from the flyback could be?


Thanks,
Todd

[itsdarkout]

I'm such a noob.....


So I spliced the red wire that comes from the flyback, and plugs into the neckboard. I took the old connector piece from the old flyback, and connected it to the new flyback via a buttsplice. But, If I remember correctly. You cannot do that, with this wire.  If thats true, could that be my problem?

The flyback is also still making a "hissing" sound. I reconnected the cap, and its secure, but its still making that hissing sound. This only started after I took the chassis back off, and resoldered some things, and touched up the flyback pins.

[itsdarkout]

Ok, turns out the flyback wasn't bad. The person who sent me the flyback must have accidently sent me the wrong one.

Well I got the right one from Chad, put the flyback in, powers up for a moment, then makes one click sound and shuts down. I'm wondering if the other flyback I put into it, (the wrong one) blew the output transistor. Or If I just need to adjust the high voltage shutdown nob.

Any ideas before I put my old flyback in, just to be 110% certain that I might just need an adjustment.

Thanks!
Todd

[itsdarkout]

put the old flyback in..... monitor works perfect. So There must be some adjustment to it.. I've never incountered an issue like this though.. Usually they just work! lol..


Any ideas?

Todd

[Kevin Mullins]

Or If I just need to adjust the high voltage shutdown nob.

Never adjust that.

If you have to adjust anything, adjust the B+ itself.

[itsdarkout]

Well....Took the old flyback out. Put the new one in.. Turned it on. Not getting the previous mentioned issue with it now. Now it doesn't even power on, and you can hear a VERY faint clicking sound.

[SirPeale]

What I really want to know is why you're f'ing around with a functional monitor.  Is the old fly arcing or something?

[itsdarkout]

Well "according" to the research I've been doing, and per the wells Gardner troubleshooting guide, replacing the flyback is one of their recommendations for a "dark picture". I've testing all the other components, I've capped it, and I've shot the tube. So this is my last attempt to bring this monitor back to some sort of "good" usage. Besides the fact that it's my monitor, and I can do what ever the hell I want to do to it, I don't think you wondering why I'm "f'ing around with it" is really any of your concern. If you don't wanna help me, thats fine. I'm not here to be belittled by you. I'm here to meet people that have the same interests in this stuff as I do. I'm no expert by any means. But we ALL gotta start somewhere!

[SirPeale]

You can do whatever you want with your monitor, that's correct.  But I've been doing this a while, and I'm still amazed when people just throw parts at equipment hoping to fix it.  Flybacks are a good example of this: usually they're either working, or they're not.  Rarely there's an in-between, but it's not often.  And there will be signs, like it buzzes, or arcs.  You didn't mention the dark picture in your initial post, just that you replaced it because "you knew it was going bad" but didn't go into any detail.  We can only go on what you post here, we're not mind readers.  I'm not here to belittle you - frankly I don't care about you one way or another.  I'm here to help the monitor.

You said you tested every component on the board; did you unsolder each one, test it out of circuit, and replace it?

Have you checked R811?  That can happen on this series, and will produce a very dark picture.

[SirPeale]

Oh yeah, your new issue (shutdown): something got moved out of whack.  This model monitor is particularly sensitive to B+.  Nudge the pot DOWN a HAIR  Fire it up again.  If it doesn't work, do it again.  Meter it to see how close it is.