ID 2 Monitors and Many Questions (Pic Heavy)

DarthSonic

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I have 2 monitors, each with curl at the top of the monitor. The picture on both monitors also "twitch" (doubt I'm using the correct term) sometimes. My speculation is cap kit, but I need a positive ID on both monitors and also want to be sure of some settings on the monitors.
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First up is my Space Invaders. The cab is a Midway's Space Invaders that has been upgraded with a color monitor and a Japanese Space Invaders DX. I read on another thread here that sometimes curl can be unavoidable if a newer board (DX was made in 1994) was used with an older monitor (although I have no clue what this monitor is). If that is the case and the curl isn't damaging anything then it is not the end of the world. However, if fixable I'd like to fix it.

Anyways, here are pics of the curl in the menu and on the monitor test screen:
IMG_20120702_190841.jpg

IMG_20120702_191456.jpg


I cannot find definitive markings on the monitor chassis, however there is a sticker on the tube labeled WG45960. Here are some pics of the monitor. If more are needed for a positive ID, or if anyone knows where the model number would be listed please let me know.
IMG_20120703_194813.jpg

IMG_20120703_194757.jpg

IMG_20120703_194750.jpg


Here is a sticker next to the monitor that may help. Even if it doesn't, what exactly do vertical/horizontal raster and vertical/horizontal damping adjust?
IMG_20120702_192849.jpg


One more question on this monitor. On the yoke, there are these plastic pieces around the white plastic (look like spacers so the yoke doesn't go too far up the tube). There is space between those and the tube. Should the yoke be slid up, or would that not be the problem?
IMG_20120702_193030.jpg
 
Next up, is the monitor in my Captain America and the Avengers. Similarly, this one also gets curl after being on for a few minutes and also twitches/shakes a little.

In this one, the whites bleed red a little also (visible in the black space between comic strips). Is this from the flyback being turned up too high?
IMG_20120703_200340.jpg


Here is a pic of the curl.
IMG_20120703_200419.jpg


Here is a pic of the monitor. Please help me ID this one also.
IMG_20120704_161133.jpg


On this monitor, both the chassis and the tube have this sticker (WG728910).
IMG_20120704_161043.jpg



Any and all help is greatly appreciated. If more pics are needed, I'll be happy to oblige.
 
top one is a WG 4900.

second is a WG K7000.

both suffer from failing caps allot.

replace the caps and readjust and you will be good.

Peace
Buffett
 
top one is a WG 4900.

second is a WG K7000.

both suffer from failing caps allot.

replace the caps and readjust and you will be good.

Peace
Buffett

Thank you very much for the quick reply! Does anyone know what the raster and damping dials affect (for when I'm adjusting after the cap replacement)?
 
turn them and watch the screen.

they control the linearity of the picture mostly.
its the width between the scan lines.

you will need to watch it for your self to see exactly what they do.
and adjust the pot till it looks the best to you.

Peace
Buffett
 
turn them and watch the screen.

they control the linearity of the picture mostly.
its the width between the scan lines.

you will need to watch it for your self to see exactly what they do.
and adjust the pot till it looks the best to you.

Peace
Buffett

Thanks again, you've been very helpful!
 
Yes, a WG4900 is the same as a WGK4900

Most of us call wells monitors:
K7500
K7000
K4900
K4600
Etc...

4900s are my favorite classic chassis.. Flybacks hardly ever fail, and even chassis with original caps still fire up and look good.. Damn things amaze me.. Just wish the image controls were a bit more robust.. But it's a classic!
 
On the first monitor you do not have curl, but vertical foldover. Simply reduce the V.size.

I'm finding it very difficult to see any "curling" on the second one.
 
Yes, a WG4900 is the same as a WGK4900

Most of us call wells monitors:
K7500
K7000
K4900
K4600
Etc...

4900s are my favorite classic chassis.. Flybacks hardly ever fail, and even chassis with original caps still fire up and look good.. Damn things amaze me.. Just wish the image controls were a bit more robust.. But it's a classic!

Thanks! Low flyback failure is a relief..
 
On the first monitor you do not have curl, but vertical foldover. Simply reduce the V.size.

I'm finding it very difficult to see any "curling" on the second one.

Interesting. I will have to try adjusting the V.Size then. Would a cap kit still be needed to keep the picture from shaking?

It's much easier to see in person than in the photo (colors too similar in the photo), but the top of the box that says "Stand By" curls to the right a bit (not too bad though).
 
depending on what you call shaking.

some games like MKII shake normally.
others don't.

so if it is the game then its fine.
if it is not the game then it could be caps or a dirty/broken adjustment pot.

but look at it this way the caps are 30+ years old in theses monitors.
so why not give them new life with a cap kit and re-flow. a little lov'in goes a long way.:)

but curling is a sign of failing caps most times. some times you can adjust it out but it will continue to get worse over time.

Peace
Buffett
 
depending on what you call shaking.

some games like MKII shake normally.
others don't.

so if it is the game then its fine.
if it is not the game then it could be caps or a dirty/broken adjustment pot.

but look at it this way the caps are 30+ years old in theses monitors.
so why not give them new life with a cap kit and re-flow. a little lov'in goes a long way.:)

but curling is a sign of failing caps most times. some times you can adjust it out but it will continue to get worse over time.

Peace
Buffett

I'm definitely going to recap both. In the WGK7000, I can see one cap is rusted right along the stress relief in the top. It can't hurt to replace them all.

As far as shaking, in both the whole picture moves up and down slightly. Captain America is less noticeable, but happens more often. Space Invaders does the same but happens randomly. In this one, I played with the V-Hold and the shake would stop for at most 2 minutes but would then return.
 
yea start with a cap kit and if the problem persists then some of your pots may be dirty/cracked and need to be replaced.

Peace
Buffett
 
DarthSonic said:
Would a cap kit still be needed to keep the picture from shaking?
Not guaranteed to fix the problem, but it would be a good place to start.

It's much easier to see in person than in the photo (colors too similar in the photo), but the top of the box that says "Stand By" curls to the right a bit (not too bad though).
I do see what you mean now, hopefully you just need to make a slight adjustment to the h.hold.
 
Need more help with the WG4900

Sorry to bring up an older thread, but I still cannot get my WG4900 correct. The monitor is a later revision as it has the extra circuit board with a transistor and pot for the vertical position adjustment. The PCB in the game is Space Invaders DX ( http://www.arcade-museum.com/game_detail.php?game_id=9665 ).

shots from before cap kit (for reference):
IMG_20120702_191512.jpg

IMG_20120702_190904.jpg



Here's what I've done so far:
1)cap kit to fix jiggling picture, and reflowed all the solder
-After this, picture looked like this (these are after adjusting the pots as best as possible)
IMG_20120811_151336.jpg

IMG_20120729_133158.jpg

IMG_20120728_205306.jpg




2) The problem lies within something in the vertical section of the board (since the picture is way too large and stretched out). I did a visual inspection of the vertical section of the board and found that R355 (9.9k ohms) had a small crack going the length of it. Out of circuit, the cracked resistor measures 6.54k ohms.
IMG_20120919_230134.jpg

IMG_20120928_203604-1-1.jpg


I replaced this resistor with a 10k ohm, 3W resistor (3W since the manual for early revisions label R355 as being 3W even though the resistance is different). It helped a little, but the picture is still far off from what it is supposed to be.
 
Need more help with the WG4900 (continued)

(in 2 posts b/c of photo limit)

3) Last night, I cleaned all pots related to vertical control with DeoxIt, turning them from one extreme to the other multiple times. This made the pots much easier to turn (also does not lose v-sync as quickly when I adjust v-size). However, the picture is still not right.
IMG_20121006_134906.jpg

IMG_20121006_134914.jpg

IMG_20121006_134845.jpg

IMG_20121006_134606.jpg

IMG_20121006_134615.jpg


Any help will be greatly appreciated! I'm not sure exactly where to go next (replace pots and test diodes maybe?). Also, there is a little space between the yoke and the tube. Should I leave it alone, or try sliding the yoke up?
IMG_20121006_134407.jpg
 
Wow, a Linearity and fold over going on. Have you checked the pots to make sure they are the right value and actually working? Since you've done the caps the next thing would be the pre drive IC or some other discrete part. I know that doesn't really help narrow things down though.

I'd also tripple check to make sure that you put the right caps in the right places and that none are in backwards.
 
Wow, a Linearity and fold over going on. Have you checked the pots to make sure they are the right value and actually working? Since you've done the caps the next thing would be the pre drive IC or some other discrete part. I know that doesn't really help narrow things down though.

I'd also tripple check to make sure that you put the right caps in the right places and that none are in backwards.

Next time I pull the chassis, I will check the caps again. I have not checked the pots, but they were in the chassis when the only problem was a shaking picture. I notice changes when each pot is turned, so they at least work to some extent. What are linearity and fold over caused by (in general at least)? Others said it could be a convergence issue..... could that be caused by the yoke not being up all the way? I reflowed all the solder on the neck board and the chassis. When soldering, I try not to keep the iron on the board too long but if the heat from my soldering iron took out a diode, might that cause this issue?
 
What are linearity and fold over caused by (in general at least)? Others said it could be a convergence issue.

Convergence wouldn't cause problems like that. If you have a convergence problem you would have full deflection but the colors wouldn't be lined up.

Folder overs and linearity problems are usually caused by bad caps, you've already replaced them but because the pic is WORSE now I think a cap is in the wrong place or backwards. They can also be caused by bad deflection IC's and other discrete parts that have failed. I'd start with the caps though.
 
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