4600 XY board problem

delroy666

Well-known member

Donor 2011
Joined
Jul 30, 2009
Messages
1,189
Reaction score
26
Location
Ottawa, Ontario, Canada
I have another WG 19K4600 that I'm trying to get working. After recapping it, I still just got a black screen and no glow in the neck. I measured B+ and got 160V. So, I tried swapping in the XY board from my good 4600, and lo and behold the monitor started working. After adjusting the pots I get a pretty good picture too.

So, there's obviously a problem with the original XY board. I resoldered the connector pins on it, but that didn't help. I'm wondering if anyone has any pointers for where I should start troubleshooting. Are there any particular components on this board that are prone to failure? I'd appreciate any tips.
 
There are tons of bad solder joints on that board besides just the connectors.

Make sure that ceramic tubed resistor on the foil side of the board is good and is soldered properly.

When you recapped that board, check it closely for solder splashes or shorts to adjacent connections/traces. The caps you replaced were put in with the correct polarity weren't they?
 
Ken, thanks for the suggestions. I double-checked the polarity of the caps and they were correct. I also checked that ceramic tubed resistor and it measured 22 ohms exactly. I resoldered it, and reflowed all the joints on the bottom of the board. While I was doing this, I noticed a solder bridge between the right leg of the V-hold pot VR301 and the nearest lead of resistor R359. Strange, since this isn't near any of the capacitors that I replaced, so the previous owner must have done this. That bridge is not present on my working XY board. So, I removed the bridge and tried the board in the monitor. It works! Sort of...

I got a nice, bright picture, but it was way out of sync - scrambled dashed lines and a rolling image. I adjusted the V-hold and H-hold pots and L351 and got rid of the rolling, but now I have a shrunken image repeated 3 times down the monitor. I can't seem to adjust it out. I attached some pics to show what I mean. Pic 1 is with my good XY board swapped in showing a test pattern for reference, Pic 2 is the 'bad' XY board showing the same test pattern, and Pic 3 is a Pac screen that I think illustrates the problem more clearly.

Any ideas?
 

Attachments

  • 19k4600goodXY.JPG
    19k4600goodXY.JPG
    42.4 KB · Views: 20
  • 19k4600badXY.JPG
    19k4600badXY.JPG
    58.3 KB · Views: 22
  • 19k4600badXYpac.JPG
    19k4600badXYpac.JPG
    39.2 KB · Views: 31
Last edited:
I was going to say... Take the known good working vert/horz board and count the turns on L351 until it bottoms out. Take the problem vert/horz board and match the number of turns on L351 to the working one and see what you get. It may not be dead up nuts on, but it should put you pretty close.
 
Okay, I adjusted L351 through its full range and it comes pretty close to fixing the problem when at its fully counter-clockwise position. I need to turn the H-hold pot VR351 all the way up (to its max resistance, measuring 45 kohms) to stop the picture from rolling horizontally. At that point I have about 1.5 overlapping test patterns visible on the screen instead of the 3 I had before.

In comparison, the good XY board has VR351 set at about 35 kohms and L351 seems to be adjusted roughly half way through its range. I guess that means L351 is messed up on the 'bad' XY board? Should I put another resistor in series with VR351 to compensate and see if that'll fix it?

Thanks for the tips guys, I really appreciate it.
 
I was going to say... Take the known good working vert/horz board and count the turns on L351 until it bottoms out. Take the problem vert/horz board and match the number of turns on L351 to the working one and see what you get. It may not be dead up nuts on, but it should put you pretty close.

That's a good idea.. I'll try it tomorrow. I could even swap L351 from the good board.
 
Success

Bingo! I ended up swapping in L351 from the known working board. I set VR351 to its centre and slowly turned L351, starting at the full clockwise position and got a good picture on the first sweep, easy as pie.

Funny thing is, I put the 'bad' L351 in my other board to see if it would work. I repeated the same adjustment procedure and after about 3/4 of a turn from the start, I got a good picture! WTF? I don't know why it wouldn't work in the other board. I must have tried it 10 times, doing extremely slow, full sweeps and could never get it to lock on.

Anyways, I have two working monitors now so I'm a happy camper. Thanks again for the help guys.
 
Back
Top Bottom