RFM WG19k7302 CRT vertical hold freaking out

sslakkerr

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Problem - Vertical hold is unstable, picture jumps from steady to a hor. line and back

Capped monitor to regain color and brightness, picture was just dull and dark. Had no problems prior to capping. Used a BR kit. All was good, so I thought. It brought back the colors and contrast in the picture, but within a minute of running the vertical hold starting falling off, flickering, then to the point of dropping to a horizontal line in the center of the monitor. By adjusting the V-HOLD u can make the picture come back, but it will just fall back to a hor line. I've read about some of the usual culprits, like IC3, but it will display fine and then jump out of hold to that band or roll so I'm not confident those things are the problem. Any help is much appreciated.

Link to video of the problem:
http://s434.photobucket.com/albums/...tion=view&current=2011-09-15_21-09-21_881.mp4
 
I reflowed the v-hold pot but there was no change. I did not hit the vertical ic nor the yoke. I'll give those a try when I get home from work. I'd guess the yoke solder would be more likely since i had to remove that part from the tube versus the IC. I don't know which chip is the IC; the chassis diagram on WG site blows. Pic below if anyone could point it out.

Link to chassis pic:
http://i434.photobucket.com/albums/qq65/0dw0/Outrun MAME/2011-09-14_22-00-47_757.jpg
 
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Well I'm close. I had some success resoldering things, but the problem is still there, just much less frequent, and typically just looses sync, not going into full v-collapse.

I addressed the yoke plug by reflowing all of the leads and redoing the solder on the vert yellow wire pin

Checked IC302 leads; looked fine

re-soldered a bunch of the caps that had dull looking solder (I really couldn't see anything that was clearly bad), focused on ones in the vertical sync path according to the schematic on randyfromm; pulled the old solder this time

I replaced a cap that was missing in the kit with one I had pulled and checked out

Since the problem changed I know I hit upon it in one of the above steps. I think I made a cardinal sin and screwed myself by not removing the old solder when i did the cap kit...i just heated, pulled and dropped the new in, with a little fresh solder. This time i replaced the old solder completely on the ones I rehit.

Looks like I'll be re-doing every cap i put in...fml. getting sick of going through the fear factor test of discharging the tube
 
check the solder on the header pins where the video input connector plugs in. ALso check width coil(if it has one) etc.. you are readjusting the holds after reinstalling correct?
 
Yep, playing w the v-hold, size, etc. .. i have been brave and stuck my hand in there to wiggle all the plugs to the chassis and neck board, including the video input plug, and saw no change.

So I left the machine running for about an hour and the picture has stabilized for the most part; it's playable now, but will occasionally roll; actually i've been playing it cause heck, that's what i got it for. I'm also noticing that the colors seem bland, but every now and then (like several minutes) it will flash brighter colors..bright like i would actually like to see it showing.

So basically it warms up and works a lot better and flashes little glimmers of awesomeness (colorwise). Is this typical of bad solder points? There are a few old caps that remain since they were not part of the kit...I am wondering if having some new and some old is an issue..
 
id definately replace the old caps, could be part of your issue and just do em to eliminate them as a suspect...

the fact that it gets better over time, after fiddling around screams solder joint to me, could be something else too but next time it gets bad enough to drive you nuts check over very solder joint man. Itll take time but you may just find the culprit. If this has a heatsunk mounted ic to drive the vertical video thats something is really be checking for cold solder joints..

did you ever id what monitor that is?edit- nevermind...k7300.. " a real gem" lol...
 
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so just to put closure on this, although with a bit of mystery, it is working great now, but I didn't do anything else to it. I had played it a bit w the random vert hold loss then shut it down. I turned it on again later that night and it looked good and was steady. for the past 2 days i've fired it up to see how it looked (and of course play) and it's been steady and working well.

Do some caps "break in" or something? I'm at a loss, but it works so I ain't complainin'!

Thanks for the help guys
 
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