Author Topic: Fried WG K4600 Monitor (Read 5400 times)

SirPeale · « **on:** May 23, 2005, 08:19:33 pm »

Picked up this monitor for free from Rob Carroll.

Been sitting on it for months, figured it was time to see what was wrong with it.

Ordered a cap kit from Zanen Electronics. As I was doing the kit, I noted the charring on the neckboard as indicated in the photo.

Ran a section of wire to bypass the shorted and blackened circuit board. Upon turning it on, it promptly started to smoke in that region.

Not sure where to start troubleshooting on this one.

Edit: here are some better, clearer pictures. The camera likes lots of light!

Ken Layton · « **Reply #1 on:** May 24, 2005, 01:48:03 am »

On the neckboard check ceramic disc capacitors C404, C405, C406, and C407 for shorts. Check resistors R418 and R419 for opens (you need to unsolder one end of R419 to check it. If these all check out, then you picture has an internal short in the screen section. This could be fixed on a picture tube rejuvenator.

SirPeale · « **Reply #2 on:** May 24, 2005, 08:38:41 am »

To check for shorts on a cap, do I just check to make sure the legs aren't twisted together or something?

cw · « **Reply #3 on:** May 24, 2005, 08:49:11 am »

Quote from: Peale on May 24, 2005, 08:38:41 am

To check for shorts on a cap, do I just check to make sure the legs aren't twisted together or something?

twisted or an internal short.......

Ken Layton · « **Reply #4 on:** May 24, 2005, 10:11:59 am »

Look for an internal short. Use an ohmmeter.

SirPeale · « **Reply #5 on:** May 24, 2005, 10:28:34 am »

I just checked R412, R413 and R414 (plus some other random resistors on the board) for continuity and I got absolutely *nothing.* Only one of the resistors I checked for continuity actually gave me a reading.

Ken Layton · « **Reply #6 on:** May 24, 2005, 10:52:08 am »

You're not looking for just continuity on the resistors. You're looking at their resistance. The resistors should be close to their stated value, usually + or - 10% is allowable. In other words a 100 k resistor could read as low as 90 k or as high as 110 k to be considered good.

Check those two resistors I mentioned earlier, R418 and R419 for value. I've seen R419 fail before (go open), but you must unsolder one end of it to test it first.

It looks like something in your "screen" voltage section is what's burning up your board. Remember that on that model the screen voltage is 890 volts DC!

Be sure to swab all the burnt stuff and soot off the board with a q-tip cotton swab and some 99% rubbing alcohol.

SirPeale · « **Reply #7 on:** May 24, 2005, 11:18:44 am »

I'll swab it in a bit.

But I should get continuity reading from a resistor that's okay, right? I'm checking from the top, from each side, and getting nothing. Or do resistors have some way of negating a continuity check?

SirPeale · « **Reply #8 on:** May 24, 2005, 12:13:56 pm »

Good call on the alcohol. It removed dirt I didn't even know was there!

Ken Layton · « **Reply #9 on:** May 24, 2005, 11:40:09 pm »

if you have a digital readout multimeter, don't use the continuity test. It only beeps on resistance of 20 ohms or less. You need to actually set the meter to one of the DC ohms scales.

SirPeale · « **Reply #10 on:** June 26, 2005, 06:54:23 am »

Thanks to my new job, I have access to a rejuvinator! Although it's known to break more tube than fix them, guy I work with states that it's diagnostics work just fine.

Tube's shot. Too bad, it only has a little burn.

Now to try and find a tube. Off to the dump!

MonitorGuru · « **Reply #11 on:** June 26, 2005, 07:36:21 pm »

Looks like that neckboard was submerged in water at some point (the white residue).

SirPeale · « **Reply #12 on:** June 26, 2005, 08:33:51 pm »

Doesn't look like scale, more like grime.

SirPeale · « **Reply #13 on:** August 29, 2005, 10:33:12 pm »

Well, I swapped the tube. Only thing it did was make bigger sparks.

Going to print this thread and bring it to work, so I can *finally* do the tests that Ken recommended.

How hard is it to swap out a neckbord? There's a junk 4600 chassis on the shelf I've been eyeing.

SirPeale · « **Reply #14 on:** August 30, 2005, 05:27:06 pm »

Quote from: MonitorGuru on August 30, 2005, 09:32:54 am

Quote from: Peale on August 29, 2005, 10:33:12 pm
Well, I swapped the tube. Only thing it did was make bigger sparks.

Umm, did you doublecheck the pinouts of the tube(s)? It could be they put the wrong tube in originally causing the problem and you replaced it with an identicaly (wrong) tube as well.

A wrong tube / pinout could definitely cause a nice lightshow around the neckboard.

I've been lead to understand that the number of pins on the neck was the indicator, and the pinout for the tube should be the same from tube to tube. You're telling me that's not correct?

And the tube is the original tube, so I doubt that they got it wrong the first time. It had a lot of burn.

SirPeale · « **Reply #15 on:** September 05, 2005, 04:59:51 pm »

One thing to note here is that the pin that's frying isn't the big red wire, it's the black ground.

SirPeale · « **Reply #16 on:** September 07, 2005, 01:07:36 am »

*bump* I've checked the resistors, they seem to all check out.

Ken Layton · « **Reply #17 on:** September 07, 2005, 02:38:13 am »

Could be shorted spark gap caps inside the CRT socket on the neckboard or shorted ceramic disc caps on neckboard.

SirPeale · « **Reply #18 on:** September 07, 2005, 08:17:07 am »

Things like shorted connections inside the socket can just *happen*? What's the cause?

SirPeale · « **Reply #19 on:** November 04, 2005, 08:45:33 am »

Got a replacement neckboard from a guy @ East Coast Amusements. Now I just need to find the time to wire it in.

Ken Layton · « **Reply #20 on:** November 04, 2005, 09:48:48 am »

Let us know if that fixes your monitor.

SirPeale · « **Reply #21 on:** November 05, 2005, 09:39:53 am »

Quote from: Ken Layton on November 04, 2005, 09:48:48 am

Let us know if that fixes your monitor.

I shall. Just looking for the time to actually perform the surgery.

SirPeale · « **Reply #22 on:** November 23, 2005, 07:00:27 pm »

So as I'm walking out the door, I see the monitor on the shelf. I figure it'll take me just a couple minutes to swap out the neckboard.

Goes without a hitch. Decent time, 20 minutes, considering I've never done this before.

Put the neckboard on the tube. Hook up power, no signal yet, I first want to know what's going to happen. Will it fry? Will it?

...wait...

...I know that sound...

HOLY COW! HIGH VOLTAGE!

Check the screen...RASTER! WOO HOO!

Power down...hook up signal. Hmmmm...I see picture! Totally out of sync, but there it is. Adjust sync...wow! I can see Mortal Kombat (what we use on our test bench)! Turn down the screen control a bit, turn up the brightness...wow...the picture looks...GOOD!

Remember I said above that I swapped the tube? I didn't even have to adjust convergence. How's that for lucky?

Ken Layton · « **Reply #23 on:** November 23, 2005, 07:05:09 pm »

So the monitor works good now?

SirPeale · « **Reply #24 on:** November 23, 2005, 07:15:30 pm »

Quote from: Ken Layton on November 23, 2005, 07:05:09 pm

So the monitor works good now?

Er...yeah! I thought I made that clear.

No?

The monitor works super-sweet now!

Ken Layton · « **Reply #25 on:** November 23, 2005, 11:55:23 pm »

How about a screen shot of this monitor in action?

SirPeale · « **Reply #26 on:** November 24, 2005, 09:10:57 am »

Quote from: Ken Layton on November 23, 2005, 11:55:23 pm

How about a screen shot of this monitor in action?

I'd be happy to oblige, but:

1) it's at work.

2) camera is broken.

But for the visual: it looks like a working K4600 with a new tube.

fredster · « **Reply #27 on:** November 24, 2005, 10:31:33 pm »

Good Job Peale!

You are getting to be a very skilled tech.

Now you need to enhance that job situation! Good luck!

Ken Layton · « **Reply #28 on:** November 25, 2005, 12:25:48 am »

You see----there's still plenty of life in old monitors!

The 4600 series has the best picture of all time.


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