Space Invaders help needed UPDATE 12/26

[y-bot]

I picked up a non-working Space Invaders upright for $50 today and I don't know where to start. The neck part of the monitor lights up and there is a slight hiss or something coming from the speaker. Nothing else. What do you I do next? Test the power supply voltage?

y-bot

[FABombjoy]

Yes!

http://www.elektronforge.com/TestMdwPS.htm

Also, reseat all socketed chips & clean the daughterboard edge connector.

[y-bot]

Thank you! I found that website earlier and that was my next step. Here's some pics:

http://portland.craigslist.org/clk/sys/466435149.html

y-bot

[y-bot]

Okay, I checked the power supply voltages and they seem okay. Is 5.2 volts or so okay? I have an analog volt meter. The +18 seemed a little low but there is no adjustment for it anyway. I cleaned the connection between the motherboard and daughterboard and the other connectors. How do the coin door mechanics work? There's something hanging down that might be to check if the door is closed or not. What do I do next?

Thanks, y-bot

[98PaceCar]

Does it do anything if you try to coin it up and start it?

[FABombjoy]

Is that 5.2v at the supply or on the board? Either way it's probably ok, but I tend to shoot for 5.1 at the board. Low +18 is ok.

Next would be to check the power on reset. Dunno about that potential coin door lockout you're talking about, typically they cut power to the entire cab. Maybe it's part of a tilt switch?

[y-bot]

@FABombjoy-Yes, it looks just like a tilt switch on a pinball machine. In the manual it is called a door switch and it's hanging loose because the lock has been removed from the coin door. I tested the power at the motherboard and got the same readings as on the power suply board. The audio is about 16v.

@98PaceCar-When it's on the neck of the monitor glows and there is a slight sound coming from the speaker, that's it. I'm not sure how to coin it up. Flipping the wire on the coin slot makes the counter on the door change but nothing else. Should I just need to do that and press start? There's no test mode on this game, right?

Also the ground pin on the cord is broken off, could that make a difference? We don't have grounded outlets here at work anyway so If it had the pin I would be using an adapter.

Thanks, y-bot

[y-bot]

Coining it up and pressing start does nothing. There is a tiny amount of hiss coming from the speaker (it stops if I unhook one of the wires) but it does not change when I adjust the volume. I haven't messed with the brightness yet but the game is definitely not playing. I read somewhere that sometimes the ROM chips need to be reseated so I pulled one out and either I broke a pin or it was already broken. I was pretty careful not to bend the pins when I pulled it out but the leg stayed in the socket. Is Elektronforge the best place to buy the replacement ROM chips? It seems like they will take a long time to ship. if the leg was broken on the ROM chip before would that make the game not work at all?

Thanks, y-bot

[FABombjoy]

I have a set of 'CV' SI roms if you want to try those.

First, remove all of the ROM chips and power it up. You should see a pattern of lines on the screen that shift when you close the tilt switch. If you still get nothing with the roms removed, and the power-on-reset line is good (should read as ground with power on), then it sounds like board issues.

[y-bot]

Sending the boards off today to be repaired. I hope that's the problem. Thanks for all the help so far, I'll keep you updated when I get them back.

y-bot

[y-bot]

I don't have the boards back yet but I asked Alex if the problems with the boards would have caused nothing to appear on the screen and he said no. It should have been garbage. So assuming the boards and power supply are good and the neck of the monitor lights up what do I check next? I'm pretty afraid of screwing around with the monitor but is there something simple I can check?

Thanks, y-bot

[FABombjoy]

When you see the neck glowing, it's usually a good sign that a large part of the monitor is functioning since the heater is driven by the flyback transformer. However, in some old WG monitors, the heater is tapped into the monitor's main transformer instead. Can you hear the 15khz squeal at all? If you can read the monitor type we can double-check against the schematic.

Try turning up the brightness and/or screen/G2 controls. You should see the screen brighten up & lines appear.

I have some CV boards that don't work & don't display anything, so screen garbage doesn't always appear.

[y-bot]

I did check the power supply and I checked the power at the board. I got a better multimeter so when I get the boards back I'll check it again. The monitor is a Wells Gardner 19v1001. I probably won't do any more work until I get the boards back but I just wanted to get some advice on where to start. Thanks for all the help so far.

y-bot

[FABombjoy]

I was thinking you might have one of those, and the heater filament is tapped from the main transformer, so glowing isn't an indication of functioning.

[y-bot]

So it could be the transformer on the monitor board?

y-bot

[FABombjoy]

Not enough info to tell what it is...

The short story is: on many monitors, the heater is driven by the flyback transformer, which in turn is driven by the horizontal deflection circuit. So... in those cases, a glowing neck means that a lot of things are at least somewhat working.

However, on that type of WG monitor, the heater is driven by the monitor's primary transformer, so in this case the glowing just means that it's plugged in.

Did turning up the screen / brightness control have any effect?

[y-bot]

I haven't messed with it yet. I did try turning up the brightness before and that didn't seem to do anything. I'll probably wait until I get the boards back before I do any more work on it. Should be the end of next week or the start of the next one I hope. They're done and payment should be there soon.

y-boy

[y-bot]

I got the boards back and now the game plays with no picture. I rechecked all the voltages at the board and everything is fine. The neck on the monitor lights up and nothing else. I checked the two fuses on the monitor board an they are okay. I've adjusted the brightness and contrast and they don't change anything. I don't know what the G2/screen control is. Here's a link to a pdf of the manual:

http://www.arcadeworldllc.com/images/Scans/Monitor%20Schematics/Wells%20Gardner%2019V1001%2019V1003%2019in%20and%2 023in%20B&W.pdf

Can you show me where that adjustment is? What's next?

Thanks, y-bot

[y-bot]

I think I figured out what one of the problems is anyway.

http://www.hevanet.com/ccorner/eeeee238.jpg

The red wire coming out of the anode is unplugged or broken off of the part where it plugs in to the monitor board. I assume the monitor needs to be discharged before trying to plug that in, correct? Is it unsafe to touch that wire to see if the end is broken?

Thanks, y-bot

[y-bot]

That was it, it works great now! Thanks for all the help.

y-bot

[y-bot]

The blacklight is lighting up but you can't see the background from the front. Do blacklights get dim over time or something else wrong?

y-bot

[y-bot]

I don't know which type it is. It's purple and 12"-18" long. The bulb lights up but you can just barely see the background from the front if you stare really hard.

y-bot

[FABombjoy]

Only an unplugged anode? That's like the monitor equivalent of the easy button :D

[y-bot]

I can't believe I didn't notice that before yesterday. The board needed repair anyway so I'm glad I got that done.

y-bot

[y-bot]

I'm still having no luck with the blacklight. Could it just be that the room needs to be dark? I replaced the bulb and the starter and you can see the bottom 1/3 of the moon barely. Could the light be getting too low of voltage or something? It doesn't look anything like the pic on klov:

http://www.klov.com/game_detail.php?game_id=9662

y-bot

[DogP]

I believe it's supposed to have a white black light... it's a white bulb that outputs a purplish color, but brighter than the typical black light. They're pretty hard to find locally (most places have regular white bulbs or the purple black lights), but you can get them online from lots of places.

DogP

[diskoboy]

I found a place that sells replacement UV bulbs. The only problem is, it's in England, shipping might be a big hassle.

But the good thing is they work in both Taito and Midway machines. But I'm not sure if the voltage may be different.

http://www.thinvaders.com/parts.html

Arcadeshop.com also has a pretty good selection of UV bulbs.

[DogP]

Most bulb places sell white black lights... here's one from bulbman.com :http://www.bulbman.com/index.php?main_page=product_bulb_info&products_id=13013 ... I can't think of the other online bulb sellers though.

DogP

[y-bot]

The machine was left on for a few days and when I came to work today the screen was solid white. You can still hear the game playing when you coin up. If you move the contrast knob back and forth the screen will appear normally for a second and then back to white. I moved it around for awhile so I don't think it's just dirty. Is the adjusting pot bad or something else?

Thanks, y-bot

[y-bot]

I cleaned it today and it didn't do anything. Now, no matter what I do with the contrast knob the screen is solid white. Are there other electronic components tied in to that contrast pot that could go bad?

y-bot

[InsaneDavid]

Possible that the pot itself needs to be replaced considering you were able to use it to tune the picture for a split second and now it's completely unresponsive after cleaning?

[y-bot]

My friend who knows a little more than me about general electronics looked at it today and thought it might be a resistor or capacitor. If you turn the brightness all the way down and turn the contrast knob back and forth it still makes the correct screen appear for a split second. he had some explanation for it but I can't remember what he said. He's no monitor expert though so I'm taking his advice with a grain of salt.

y-bot

[y-bot]

I installed a cap kit but that didn't change anything. I guess I'll replace the contrast pot next. Where's a good place to buy one? Any chain stores that might be in my area carry these. I don't see them on Radio Shack's website and I don't know of any other places that carry that kind of thing. The pot is marked "1377813" and "40X0585-090" and according to the manual it's 250 ohm. Any other suggestions on what could be wrong?

Thanks, y-bot

[y-bot]

My friend and I tested the contrast potentiometer and it seems to be functioning correctly. Any idea what else could be causing this problem? I'm having no luck finding any sort of troubleshooting guide for this monitor besides the manual.

y-bot