WG K4600 - Won't Focus

[SirPeale]

Picked one up recently.  Ordered  cap kit, waiting for it to arrive.

The monitor was filthy when I got it, but a damp sponge took care of the worst of it.

It has a nice bright picture, problem is it's out of focus.  The focus pot seems to just spin with no resistance, and has no effect on the picture quality.

Can I replace the pot?  What kind is it if I can?  Or do I have to replace the whole flyback?  It seems that this pot is separate from the flyback.

[Ken Layton]

It's usually either a bad CRT socket assembly on the neckboard or a problem with the focus grid inside the picture tube itself. Usually rejuvenating the tube will fix it.

However, first put in a capkit before doing anything else to see if that fixes it. Remember to resolder the numerous bad solder joints on the foil side of the 4600's main board, too.

[SirPeale]

It's usually either a bad CRT socket assembly on the neckboard or a problem with the focus grid inside the picture tube itself. Usually rejuvenating the tube will fix it.

Oh good, an expensive fix.  

However, first put in a capkit before doing anything else to see if that fixes it. Remember to resolder the numerous bad solder joints on the foil side of the 4600's main board, too.

Will do when it arrives.  Any particular ones to look out for?

[Ken Layton]

The worst bad solder joints are on the connector pins for the hor/vert ("X-Y") board, video interface board, and the power regulator board.

I always unsolder the two wires going to the seperately mounted width coil to keep from damaging it while recapping. Remember to reconnect it when done (doesn't matter which of the two brown wires go to which terminals on it).

If you have a rejuvenator handy, I'd put the picture tube on it now to confirm condition of the focus grid. If the rejuvenator says it's ok then likely you have a bad socket assembly (costs about $10 to buy from Wells-Gardner).

[SirPeale]

If you have a rejuvenator handy, I'd put the picture tube on it now to confirm condition of the focus grid. If the rejuvenator says it's ok then likely you have a bad socket assembly (costs about $10 to buy from Wells-Gardner).

Regretably, no.  There's a TV shop up the road from me, but it'd cost me ~$100 for them to do anything.  

[Ken Layton]

It might be worth your while to invest in the purchase of a rejuvenator on ebay.

I have a rejuvenator and use it all the time.  

[SirPeale]

Yes, but you work on monitors all the time!  It would be worthwhile if I did too, but I might use it twice, if I'm lucky.

If you were nearby, I'd drop by your place.  I don't know anyone locally (except the TV tech) that does this stuff.

[MonitorGuru]

Honestly, for your situation (which is similar to mine though I like to work on them a bit more, but only as a hobby), just do a tube swap and toss the bad tube, if that's the actual problem.

Actually, go find ANY tube+yoke that is closely compatable and quickly swap it in, before even doing any cap kits or other diagnosis.  The time will be about 40 minutes start to finish even for a novice.

Even if the yoke isn't the best (geometic problems), you can see if the other tube causes the same focus problems.  That way you'll know if it's the tube or if it's the flyback/cap kit/other problems.  

If it is the tube and no geometric problems, TADA you're done.  if it is the tube with geo problems, look for another tube+yoke that is closer to the same resistance, or do a yoke swap.

If it's the chassis then swap back in the original tube and then do a cap kit and go from there.

Good luck!

[SirPeale]

Then comes the problem of finding a tube. Esp a compatible one.  I've been keeping an eye out for TVs, but have had zero luck so far.

[SirPeale]

Well...congratulate me.  I just broke my cap kit cherry!

It was pretty straightforward.  Hardest part was disassembing the monitor itself.

While I had it apart, I stuck it in the sink and gave it a thorough hosing down.  It was *filthy.*  Stuck it in the oven @ 150 for an hour to dry it down.

Did the caps.  Hard finding the little buggers!  Biggest problem was removing the old solder.  I have a solder sucker that served me faithfully for years.  Then I had kids!  My oldest has been liking to pull it apart.  Finally wouldn't stay together anymore.  I tried taping it together, but the tension of the spring kept opening it up in a little while.  Halfway through, after my wife got home, I jumped in the car and got another one @ Radio Shack.

Reassembled as best as I could, took it downstairs, and plugged it into my JAMMA cab to test.  No flames!  No smoke!  It was a success!

Well...not so much.  It's still not focused.

You sure about that pot, Ken?  It has *absolutely* no resistance, and a pot should, right?

[Ken Layton]

I've never seen one of those pots go bad. It's a very high resistance pot: 25 meg ohms. This might be beyond the measurement capabilities of some ohmmeters. If you still have doubts about that pot being good, then substitute a known good one or order a brand new one (part number 204X3901-125) from the parts dept at Wells-Gardner.

[SirPeale]

When I said it had no resistance, I chose my words poorly.  By resistance, I meant that it spins freely, not that I actually measured resistance.  I'll break out my multimeter later and measure the ohms on it.

[SirPeale]

Picked up a junk 4600 chassis today from Mike Appolo.  Brought it home and replaced that pot.  It's working great!

Only one issue: along the left side there's a streak of red.  Why would that be?

[Ken Layton]

Red cutoff or red drive pot on the neckboard may be just a tad too high?

[SirPeale]

Maybe, I'll give it a shot.  Weird, though...it's just one line of pixels all the way down.

[Ken Layton]

Maybe convergence rings/yoke problems?

[SirPeale]

I tossed a convergence grid up, all the colors are meshing fine.

It's just the one line, on the very left.  Doesn't shift when I use the horizontal adjustments.

It's no biggie, it's quite minor, but I was curious, since it seems to have no cause.

[fredster]

What about shorting the Grid on the neck board like Randy Fromm shows?

You have to take out the transistor you short over.

That's the home made rejuvinator.

[SirPeale]

Think I'll pass.  It's working fine now except for that red stripe.  I can live with it.