Asteroids Spot killer, plays blind.

annaks13

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Hi everyone,

New to the forums here, so I figured I would say hello at first!

I'm trying to open an arcade in the area, and I picked up a sweet Asteroids machine. When it was at the shop, it worked for the most part. It exhibited a strange issue...when the game played, the spot killer would turn on at random intervals. then the vectors would disappear. Sound would stay, and controls still seemed to work (the thruster button would 'woosh').

I looked at it once we got it home, and everything seemed fine, except the wire-wound resistors on the deflection board. The guy I bought it from replaced R100 because it seemed to bake itself. When I would wiggle the wire harness around and play with the pots on the board, the screen would get better, but it would always go back to the spot killer/vector blinking. I know for a fact that the X potentiometer was bad. When I pushed on it with a screwdriver, the monitor would jump around like crazy.

I ordered some parts from Bob Roberts and replaced the caps and pots on the deflection board. Upon placing it in the machine, the spot killer is on constantly now. No intermittent vectors. It plays blind essentially. R100 started to get EXTREMELY HOT, so I unplugged the power, but not before the ceramic crumbled off of the resistor itself (picture attached). I started digging and read that those can be replaced with wire jumpers, so I did so, but that made no difference.

So here's where I sit now: The machine plays blind, spot killer is on constantly. 5.13v on the game board. Monitor has neck glow. If I turn the brightness up, there's a faint glow on the left half of the monitor screen that flickers. Playing with the pots makes no difference. The monitor makes a faint hum. All the fuses have continuity with my multimeter, no caps have blown. I assume that the board really isn't getting an X or Y signal now, but I'm not sure of how to check that. I don't have a decent scope at the house. I reflowed the headers, but that made no difference as well. The plug wires on the board had some very loose connections, so I cut the wires, removed the metal cap on the ends, and resoldered them to the board.

I tried emailing the guys at Elektron Forge, who were VERY nice and gave me some tips, but told me they were too backlogged to look now.

My only hope is to head home and check continuity on the wiring harness. I'm hoping to find that a couple of the wires have come loose from the pins, but that's very wishful thinking.

Can anyone help me figure out why Asteroids hates me? :)

Thanks for your help!
 

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Okie dokey, so here's an update. I checked the board and all of the connections seem good. The harness is in good shape. However, upon closer inspection, F600 has blown. I'm going to see if I can run down why after I get a new pack of fuses.
 
Solder a heavy gauge wire to the underside of those large resistors. Essentially creating a short over the resistor.

That will take care of that problem.

Next reflow all the headers on the deflection board.
 
Solder a heavy gauge wire to the underside of those large resistors. Essentially creating a short over the resistor.

That will take care of that problem.

Next reflow all the headers on the deflection board.

Hey there! I got some thick wire and went across them. I also reflowed all of the headers and doublechecked all of the cables. I replaced F600, and while it hasn't blown again, I am still getting the spot killer and the shadow on the screen.

I started looking at the bottlecap transistors. I put one leg of my multimeter on the chassis and touched each individual leg while in continuity mode. None of the legs are grounding out, although when I have the plugs plugged into the deflection board, there IS continuity between the legs of one, and the legs of another. I'm not sure if it's supposed to be this way or if there is a short somewhere on the deflection board. Just to doublecheck, I took the board out and looked over things one more time. I didn't see any soldered together pads.

I've also started putting components back. First I replaced the bridge rectifier with the old one, and now I replaced one of the smaller .5uf caps at the bottom of the board. No difference. :(
 
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Just as a helpful reference, I've attached pictures of the top and bottom of the board. Thanks for any advice you can give me!
 

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Get yourself a copy of the B&W vector monitor FAQ:

http://www.ionpool.net/arcade/tech/bw_vector_monitor_faq.pdf

and read it several times. Page 51 even has instructions on basic testing the XY output of your game board. After you do the AC test, check for DC voltage present in the Y output of the game board - if there is any, that's bad. But rereading your first post, it seems the game was working ok.

So the next thing to check is the bridge rectifier at DB100. See page 19. After that, see page 55 for a more thorough way of testing the bottle caps.
 
So the next thing to check is the bridge rectifier at DB100. See page 19. After that, see page 55 for a more thorough way of testing the bottle caps.

For the heck of it, I swapped the old bridge rectifier back into the board and checked it out. My multimeter tells me it's good.

I'll do further checking after work tomorrow. I really hope I can get this working. The whole neighborhood could enjoy this one in the shop :)
 
Ugh. This is annoying.

So I metered everything at the large connector coming from the game board, and it all looks like it's in spec. It's definitely the deflection board, based on the fact that the game plays blind, worked (somewhat) before, and that is what last changed. Because the fuse keeps blowing in F600, I'm narrowing my focus down to the transistors at Q605, Q606, Q608, and Q609.

My best guess is that when I put the new caps in, I stressed something that was barely working to begin with, causing a cascade of misery. I didn't want to have to take the monitor out of the cabinet, but it's looking more and more like this weekend will include my boyfriend and I lifting this thing out.

For future reference of anyone finding this thread, these are the proper voltages of those transistors, from the extremely sweet B&W Monitor guide as suggested by douglasgb:

Q605
Base should be +32.3v
Collector should be +32.9v
Emitter should be +30.5v

Q606
Base should be +30v
Collector should be +30.6v
Emitter should be +.2v

Q608
Base should be +.2v
Collector should be -.1v
Emitter should be +34.6v

Q609
Base should be -.5v
Collector should be -.1v
Emitter should be -31.5v

Because I have been pretty busy getting some other stuff in place for the shop, I'm not sure if I have the time to run down everything, so I'm also going to start looking for a new deflection board. It'll be a race between my Paypal account and my willingness to keep troubleshooting. :)
 
I had a similar issue with mine, and I ended up replacing two identical large capacitors on the monitor chassis. I can't remember what they were but that did it. I'll try to look it up after work.

EDIT: C100 and C101 on the regulator PCB. I have the G05-801 monitor.
 
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The nice thing is the X and Y sections are just about the same, so you can probe a 7xx part and then compare it to the same 6xx part and see where things start to differ. Same with testing the big chassis mounted bottle cap transistors - you can leave them in and compare them at the harnesses (but do check for shorts to chassis). The transistors are a good place to start and also check all the diodes.

The schematic on page 10 will help:

http://arcarc.xmission.com/PDF_Moni...Electrohome G05-802 G05-805 Monochrome XY.pdf
 
Hey everyone,

Yet another update. I replaced Q606 and 607. Now the spot killer is on, but there has been a change. Before, when I would turn the brightness up the entire way, there was just this strange flickering blob on the screen. Now, there's a single, solitary white dot. I'm not sure if this is good or bad, but either way, I kind of feel good because I've got something on the screen. I'm going to re-meter the large connector plug's voltages to make sure everything is kosher.
 
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Aaaand...back to square one. Only this time, F700 is blowing out. The only thing I am changing is the chassis transistors. If I swap Q607 out for another, F700 fries. If I leave the two transistor connectors off of the deflection board and power up, no fuses are popping. The only change is, yes, now I have a single white dot in the center of the screen if I crank the brightness up.
 
Aaaand...back to square one. Only this time, F700 is blowing out. The only thing I am changing is the chassis transistors. If I swap Q607 out for another, F700 fries. If I leave the two transistor connectors off of the deflection board and power up, no fuses are popping. The only change is, yes, now I have a single white dot in the center of the screen if I crank the brightness up.

I think you're making progress. From page 19 of the FAQ: "If at first you do not get a picture and the LED on the monitor (D504) stays lit, every time you go back to determine what else has failed in this amplifier circuit, ALWAYS check the out-put transistors Q608, Q609, Q708 and Q709 because you can destroy them as fast as you replace them."
 
Aaaand...back to square one. Only this time, F700 is blowing out. The only thing I am changing is the chassis transistors. If I swap Q607 out for another, F700 fries. If I leave the two transistor connectors off of the deflection board and power up, no fuses are popping. The only change is, yes, now I have a single white dot in the center of the screen if I crank the brightness up.

Dumb question, but are those Transistors isolated with mica insulators?
 
Dumb question, but are those Transistors isolated with mica insulators?

Hey there!

Yep, when I replaced them, I also made sure to check the casings for continuity with the chassis of the monitor. Interestingly enough, continuity IS THERE when the harness is connected to the board. Without it though, there is no continuity. So if there is a short to ground somewhere, it's happening on the board.

Just to be safe, I ordered 4 a piece of the transistors (enough for two changeovers of the complete set) and I also got some silpads coming. I know that some people prefer mica over silpads, but I could really only find silpads at the current moment.
 
Yep, when I replaced them, I also made sure to check the casings for continuity with the chassis of the monitor. Interestingly enough, continuity IS THERE when the harness is connected to the board. Without it though, there is no continuity. So if there is a short to ground somewhere, it's happening on the board.

What if you plug in the harnesses then unplug the yoke - still have continuity from case to chassis?
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The case of those transistors is the collector, which is connected to pin 3 (Qx08) and pin 6 (Qx09) in the harness. Check the pins on P600 and P700 to see which of the four are grounded, and then follow the schematics. I'd suspect D608/708 and if they're bad then Q606/706 and/or Q607/707 were probably casualties as well. See page 43 of the FAQ.
 
Okay, I went through I metered all of the transistors (mostly checking Q606/706 and Q607/707) on the board, and I found something strange...

When I meter Q503, I get a closed circuit off of the collector and emitter from the base. When I reverse the polarity and try to test it the other way, base to collector measures infinite. Base to emitter is showing closed. I don't think this is right, but I could be mistaken. Is this correct? It sounds bad to me, like something is shorted there.
 
Make sure that the wiring to the mounts for the chassis mounted transistors is intact and that they are wired correctly and not shorted. I had an issue like yours and found that someone had reversed 2 wires going to one of the mounts.
 
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