WG 19V1001 (Space Invaders)

[nickmudd]

I have a space invaders with a dead monitor. I have neck glow but no raster. No lines etc on screen. Where should I start? I would like to test the tube but I do not know how.

[boardjunkie]

Could be just about anything. Get a copy of the schematic and verify all the power rails are there before investigating further. Um....you *did* verify that there was good video output from the boardset......right?

[nickmudd]

Could be just about anything. Get a copy of the schematic and verify all the power rails are there before investigating further. Um....you *did* verify that there was good video output from the boardset......right?

The board is most likely messed up. I have no way of testing it though. The monitor doesn't show anything on screen. with the brightness turned all the way up there is nothing on screen, no light at all. I also don't hear a crackle when I apply power. To me, it sounds like there is either no high voltage or the tube is bad. But I am new to this and really don't know what is going on.....

[nickmudd]

The voltage going to the flyback is spec'd at 75V and I am getting 76.8. My HV diode doesn't seem to be any good.

[mgb]

I'm not sure that 76.8 is so bad for something spec'd at 75.

did you meter for voltage at your video input on the monitor. also sometimes those l shaped board on the midway space invaders may need cleaning and reseating if video isn't making it to the monitor.

[nickmudd]

I'm not sure that 76.8 is so bad for something spec'd at 75.

did you meter for voltage at your video input on the monitor. also sometimes those l shaped board on the midway space invaders may need cleaning and reseating if video isn't making it to the monitor.

I haven't measured the video input on the monitor. Would the screen be completely dead without video input?

[mgb]

it could appear completely dead without video, but if you crank up the screen knob on the flyback, you should see raster

[nickmudd]

it could appear completely dead without video, but if you crank up the screen knob on the flyback, you should see raster

I don't have a screen control, I only have a focus control on the board. I have discovered that I am missing 155V and 550V from page 3 of the manual. They both read way low.

[nickmudd]

I am thinking my can capacitor is bad. I will try to repair it when I get the time.

[mgb]

Are you talking about the big cap that is to the side of the board, C101?
The only thing that I find odd is that you said you have neck tube glow which means the heater is working. The heater is fed off of a winding on the high voltage unit (flyback).
So typically if the problem is in the power supply or horizontal section, I would think you wouldn't have neck glow.
I very well could have missed something and may be wrong but thats just how I figured it.
Could it be vertical collapse?

[nickmudd]

Are you talking about the big cap that is to the side of the board, C101?
The only thing that I find odd is that you said you have neck tube glow which means the heater is working. The heater is fed off of a winding on the high voltage unit (flyback).
So typically if the problem is in the power supply or horizontal section, I would think you wouldn't have neck glow.
I very well could have missed something and may be wrong but thats just how I figured it.
Could it be vertical collapse?

The heater is fed off of the power transformer. C101 is the big cap. It has 4 capacitors inside. There's a thread over on KLOV where someone posted how to change it out. C101D is the one I suspect as being bad, it (as far as i can tell) supplies 160V which is then jumped up to 600V. I'm not so good at reading the schematics though.
I also found out that the HV diode is fine, I just had to supply a larger test voltage when I checked it.

[mgb]

Oh ok. sorry, I didn't realize how the heater was fed.
Have you found a source for that cap?

[nickmudd]

Oh ok. sorry, I didn't realize how the heater was fed.
Have you found a source for that cap?

I think I read somewhere that it can be custom made, but I could also remove the old one and replace it with 4 individual caps.

[boardjunkie]

Just replace it with seperate caps. There's lots of room under the chassis to hide them. Just glue them down but don't use silicone unless it is *electronic grade* silicone. Ordinary stuff emits acetic acid that is corrosive to everything around it. You could likely find a NOS cap (I know there's a whole pile of 'em at an electronics supply near me), but I guarantee they'll be junk due to them just sitting unused. That be'n said, I would replace *every* electrolytic cap in the thing....it won't cost you much and that rules out failing caps as trouble causers.

Next, that board has a ton of pin/socket headers that hold the board down and make connection to the chassis wiring. Pull the board and reflow the solder on *all* of them. Look for any other cracked solder while yer "in there".

The power supply *must* be putting out the correct voltages before you go any further.

Just FIY, this is a composite video monitor, so you can make up a cable to run the output of a DVD player into it for testing to verify a good input signal. See the schematic (it is on arcarc). Input and gnd are P1-1 (vid input) and P1-2 (gnd).

These are bone simple monitors and among the easiest to work on.

[nickmudd]

Just replace it with seperate caps. There's lots of room under the chassis to hide them. Just glue them down but don't use silicone unless it is *electronic grade* silicone. Ordinary stuff emits acetic acid that is corrosive to everything around it. You could likely find a NOS cap (I know there's a whole pile of 'em at an electronics supply near me), but I guarantee they'll be junk due to them just sitting unused. That be'n said, I would replace *every* electrolytic cap in the thing....it won't cost you much and that rules out failing caps as trouble causers.

Next, that board has a ton of pin/socket headers that hold the board down and make connection to the chassis wiring. Pull the board and reflow the solder on *all* of them. Look for any other cracked solder while yer "in there".

The power supply *must* be putting out the correct voltages before you go any further.

Just FIY, this is a composite video monitor, so you can make up a cable to run the output of a DVD player into it for testing to verify a good input signal. See the schematic (it is on arcarc). Input and gnd are P1-1 (vid input) and P1-2 (gnd).

These are bone simple monitors and among the easiest to work on.

Do the 160V and 600V come from the power transformer? If I can find the source of the voltage I can trace it easily.

[nickmudd]

I have an update. I replaced all c101 capacitors with individual caps. I did not see anything different. I haven't checked voltages yet though. It's getting late and I have work tomorrow.


Edit: I couldn't sleep without checking. All voltages are the same as before. I checked the output from my new caps, c101a is 105V c101b is 76V c101c is 30V. My 160V is still reading the same. I have a full set of electrolytics ready to change them all out. As a side note, I have video output from the board (I hooked it up to my 25" k7000)

[nickmudd]

For anyone that is facing the same issue with this board, check all solder connections. I had a wire broken off under the flyback that leads to the collector of Q103. Soldered it back on and it works perfectly.

[nickmudd]

I spoke too soon, It was working good until I turned it off. I adjusted the B+ to 75V, then restarted the machine after a few minutes. The image was not fitting on screen and I had a wave across the screen. My B+ is now at about 94V and adjusting R212 does not do anything. Crap.....