My G08 troubles

demogo

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This thread is continuing from here:

http://forums.arcade-museum.com/showthread.php?t=237821

and here:

http://forums.arcade-museum.com/showthread.php?t=249208

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This is my OMG I can't believe I'm doing this blog along with an appeal for advice because this is the first time I've tried anything more complicated than recapping a monitor.

At the end of the day hopefully I'll have learned something, fixed this monitor, and people that come after me reading this thread will have something useful.

I lost deflection on the bottom half of my G08 on my Star Trek. Before that the image was *okay* but had issues with the graphics being jittery.

So I pulled the monitor and started by checking to see which of Mongo's G08 mods had been done to it. The voltages going in had been modded for 120v operation or 45v AC to the monitor -- just what it should be. Check! And the deflection transistors were mounted inside the heat sink rather than the default outside. Check! The power supply had been supplemented with a switching power supply to handle the +5. Check!

So all of Mongo's recommended G08 mods were complete.

So per Kstillin's advice, I swapped the connectors for the deflection transistors and fired the game back up. Surprisingly, I had deflection although I didn't exhaustively test it. When I flipped the connectors back to normal I went back to intermittently having deflection on the bottom half of my screen.

So my current advice was to start by re-pinning those connectors to the deflection transistors. Fortunately they look like standard .156 connectors and I have some .156 pins on hand. I don't have any 7 pin connector shells on hand so my plan is to remove each wire/pin, cut it, re-pin it, and re-use the same shell. Hopefully that'll be a better, more robust solution than what I have now and it certainly isn't going to hurt.

Before I started doing this I decided to test the deflection transistors with my DMM. The G08 FAQ has a nifty section on testing these involving testing each transistor in 6 different ways through their wiring harness so you don't have to even pull them to test them.

Here's what I did. I started with these instructions (formatted better for posting here). These transistors are NPN.

[FONT=Arial, Helvetica, sans-serif][SIZE=-1]1) Set your meter to the diode test. Connect the red meter lead to the base of the transistor. Connect the black meter lead to the emitter. A good NPN transistor will read a JUNCTION DROP voltage of between 0.45v and 0.9v. A good PNP transistor will read OPEN.

2) Leave the red meter lead on the base and move the black lead to the collector. The reading should be the same as the previous test.

3) Reverse the meter leads in your hands and repeat the test. (EDIT: Does the text just before this go with #2? Wasn't sure what to do with this so did nothing). This time, connect the black meter lead to the base of the transistor. Connect the red meter lead to the emitter. A good PNP transistor will read a JUNCTION DROP voltage of between 0.45v and 0.9v. A good NPN transistor will read OPEN.

4) Leave the black meter lead on the base and move the red lead to the collector. The reading should be the same as the previous test.

5) Place one meter lead on the collector, the other on the emitter. The meter should read OPEN.

6) Reverse your meter leads. The meter should read OPEN. This is the same for both NPN and PNP transistors. Thanks to Randy Fromm <[email protected]> for this excellent summary of the diode test method.

And here are my results with my DMM set to diode test where a green cell is a passed test and a red cell is a failed test:

[/SIZE][/FONT][FONT=Arial, Helvetica, sans-serif][SIZE=-1]
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[/SIZE][/FONT][SIZE=-1]So according to my testing one of the 4 transistors is good, two are train wrecks, and one is marginal.

I tried double checking some of these tests with my other el-cheapo DMM and it came up with different numbers that were higher but basically only changed one lower failing score to a pass on DT1.

Comments? Can I basically mostly have deflection with numbers like these? Or is it a "there's no way you could have deflection with numbers like that" and there's something wrong with my testing or DMM?
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Hey Rob,
I'll start out by saying wile I know a little about the workings of the game I am far from an expert and as far as the G08 monitor I have read everything I could find over the years and collected all the info I could find to prepare for the day I would have to repair one of my 3 monitors. That's right my 3 G08 monitors after all these years are still going strong and have never caught fire and I have never installed my new cap kits which I have had for over 10 years. I guess I have been extremely lucky but I always say if it isn't broke don't fix it.
With that said I did have a slight problem with one of my G08's a few years back which seems similar to your problem. I had the bottom of the screen collapse into a straight line. The problem for me was corroded pin connections on one of the paddle boards. I pulled both paddle boards and cleaned both ends of the connectors and it's been rock solid ever sense. One other problem I had was with jittery vectors. That turned out to be corroded pin connections at the power supply so it may have been a bad ground issue. Cleaning up the pins fixed that problem. I do have a forth G08 monitor which is just a pile of parts which I hope to jump in head first and do a complete rebuild to sort of get my feet wet and gain some experience with the G08 before I cap my other working monitors.
From what I have read if your monitor was working sometimes with full deflection then I don't think you would have a bad deflection transistor. They either work or they don't and when they don't you see smoke and fire.
My bet is a bad connection somewhere between the paddle boards all the way up to the deflection transistor sockets. I think they have sockets instead of being soldered on but I could be wrong.
I am sure their are a few G08 experts here that will help you figure out your problem.
Good Luck
 
wow you picked a hum dinger to start with! Im gonna guess that the transistors are fine, these generally dont fail quietly, and they take a paddle board with them. Check all solder joints on the connectors on and adjacent to the paddle board. Then check the input connectors and the connectors on that protection board.
 
wow you picked a hum dinger to start with! Im gonna guess that the transistors are fine, these generally dont fail quietly, and they take a paddle board with them. Check all solder joints on the connectors on and adjacent to the paddle board. Then check the input connectors and the connectors on that protection board.

Yeah, I was actually kind of scared to work on this monitor given it's reputation for being difficult. But it had to be fixed so what other choice did I have?

OK, I'll start by repinning the connectors coming from the deflection transistors and then look at the paddle boards.

I wish I understood why I'm getting DMM readings from the DTs that indicate bad parts.
 
Since a swap of connectors at the paddle boards restored deflection, you know you have an intermittent connection problem at the paddle board headers, the PCB headers, the connectors, the wires at the transistor sockets, the socket connection to the transistor legs. I would look at the header on the main PCB to the paddle boards, the top of the paddle boards, and finally the sockets for the transistors.

When I have been stumped by this problem in the past:

One deflection wire had the metal connector crimped so hard it cut through the wire but held onto the insulation. In some positions it made contact in others it didn't.

Solder connection broken at the socket but wires were so stiff it wasn't obvious until I removed the socket.

The tab that the wire is soldered to on the socket gets sandwiched between the insulator before it makes contact with the transistor leg. I have seen these broken in the insulator where you can't see it.
 
Thanks guys.

I decided to start with something on the list that's easy to work up some confidence so I re-pinned the connectors going to the paddle boards from the deflection transistors. Then I sprayed the paddle board header pins with Deoxit and sprayed some Deoxit into the connectors and worked them on/off the pins. So all new pins now and the paddle board header pins are gleaming.

Then I pulled a paddle board out and carefully turned it over to look for problems and I saw this:

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Some questions:

1) I drew some arrows to things that looked obviously bad to me. Looks like some broken solder joints and a solder bridge between the 3rd and 4th solder joint on the right. Do you guys agree?

2) Should there be a solder bridge between that 3rd and 4th solder joint? I got continuity on my DMM with the 3rd and 4th joints, should it be there?

3) Do you see anything else that looks bad to you that I missed?

You guys are terrific, thanks!
 

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Yea, some of your solder joints could stand to be soldered wicked and re flowed with new solder.
The solder bridge between the 3rd and 4th pin on the red female connector end is actually a trace connecting the 2 pins so thats OK. Here's a picture I found somewhere of the top and bottom of a paddle board.
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Here's the back of my second (upper) paddle board.

The solder joints look good to me but I'm a novice at this.

The only question I have is this trace near the bottom (with the red arrow pointing at it). It's covered midway with something brown -- not sure what that is or if I should be concerned.

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It looks like the bare copper trace that was never covered with solder like the rest of the traces. It should be fine unless the trace is cut or broken. You could always clean it up and put a little flux on it and flow some solder on the trace.
 
It looks like the bare copper trace that was never covered with solder like the rest of the traces. It should be fine unless the trace is cut or broken. You could always clean it up and put a little flux on it and flow some solder on the trace.

It could be just flux. Look at the rest of that board......there's a bit of flux, everywhere. It won't hurt anything. If you wanna clean if up, use a little alcohol and a q-tip.

Edward
 
Thanks guys.

So on the solder joints on the pins that look okay; should I reflow them? Or leave them alone?
 
I think the joints that are pulled away from the center of the board are OK.
I'd resolder that one at the connector header though.

All of the joints that go to the header pins that feed to the transistor sockets, I'd resolder those.
 
OK, so I guess the next step is to discharge the tube and take the monitor apart with the aim of pulling the main deflection board and looking for solder joints that need help, especially where the paddle boards plug in.

I'm not seeing which wire is the focus wire that I'm going to need to desolder to get the deflection board out? Can anyone point it out in one of my pictures or describe it so that it's obvious to me?

Thanks!
 
Pictures of my G08 here:

http://forums.arcade-museum.com/showthread.php?t=237821

Can anyone describe the wire going to the focus assembly that needs to be desoldered to remove the deflection board? I'm just not seeing it.

In the meantime I'll start by taking the other stuff out. Maybe it'll become obvious when there are less wires plugged in.

Edit: still don't see this and also don't see a connector on the deflection board to the DAG that was mentioned to me. Guess I'll just take it out as-is.

Edit 2: OK, now I see it. It doesn't run to the deflection board, the focus connector runs to the neckboard. I removed mine and it was a mess; it was barely hanging by a few strands so this will be a mess to reattach.
 
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OK, so I've gone from one extreme to another today. Unfortunately the trend is downhill.

So I did as I described above, took everything apart, fixed the broken solder joints on the paddle boards, and reflowed all of the headers on both sides of the paddle boards and on the deflection board. I'd already repinned the connectors that plug into the paddleboards yesterday.

Also used more Deoxit on the paddle board pins since I had it out anyway.

Put everything back together and triple checked that everything was hooked up correctly. The focus wire was a real PITA but I got through that although I'm not sure how good a job of attaching it I did.

Powered it up and the game came up without any red colors so I seated/reseated the connector to the xy boards and the input connector on the G08. That fixed the problem so evidently there is something going on there too.

Anyway, fired the game back up and everything seemed okay but the focus seemed off a bit so I tweaked that control and things looked nice!

In the past at times when I'd get game sounds the monitor image would sometimes shimmy a little but that seemed to be resolved. Image was solid when game sounds were happening and I powered it off and on 3-4 times and played some nice games (hit 600K once which is good for me).

Then I decided since that was all resolved that I'd fix my "sometimes flickers a lot marquee when first turned on" issue that I'd been ignoring. So I opened the marquee area up and thought I'd try the simplest solution first so swapped in a new FS2 starter. Nope, didn't help.

I noticed at that point that I was hearing kind of a hissing sound from the monitor when it was first turned on but the image was fine.

Swapped light bulbs in -- that didn't help either. Hmmmm, must be the ballast so I cut the old ballast out and wired a new one in and was surprised that I still had the same issue. WTH? I'd replaced the ballast, starter, and bulb at this point?

So I got mad and ripped out the whole marquee lighting system and swapped in one from my MAME cab. It developed a problem in the Star Trek cab as well and I moved it back to my MAME cab and it was good. And I hadn't changed anything in the process so I hooked my DMM up to the wires feeding the marquee light in the Star Trek and it reported 108V AC going to the marquee light. WHAT?

In the meantime I'd been powering the game off and on 3-4 times as part of the testing and now the hissing I'd noticed earlier was more dramatic and the monitor's image would "shudder" when it would happen. After it was on for 15 seconds everything would be good again.

So now I'm really stumped -- why am I just getting 108v to my marquee light? That's probably why it's having so hard a time starting when the game is turned on?

Oh, forgot to mention that I ohmed out the original ballast, the new one that I'd put in, and a spare and they all ranged from 28ohm to about 32ohm so I think they're all good.

So I seemed to have picked up a new problem with my G08 now -- sounds like something is arcing maybe? Not sure.

Thoughts? How the hell do I attack this problem or these problems if the weird voltage to the marquee is unrelated to my new monitor issue?

Thanks in advance!
 
First, what ST cabinet are you working on ? A dedicated or conversion cabinet. That would depend on where the marquee gets it's power. If it was a kit they provably used the original marquee fixture and wires and could have connected it to any switched AC point in the harness. If it's a dedicated cabinet then it's connected to the 115 volt AC off the transformer, the same connections as the cooling fan. 108ac is not that far from 115ac so it should not be a problem but you can try wiring the marquee directly to an ac plug and plug it into a wall plug and bypass the game cabinet and see what happens. Have you measured the AC voltage at the wall plug?
As far as the hissing sound from the monitor, that doesn't sound good. Sounds like Hi Voltage arcing. Recheck that focus wire. Not sure where it is soldered but did it have a rubber boot on it? It could be arcing at that point but to find out fire up the monitor in the dark and look for anyplace you see sparks jumping and use a flashlight so you can quickly find the exact spot where it's arcing from. I hope it's just the focus wire and not the flyback.
 
You should be able to figure out where the arcing is with all the lights out.
Look around the anode cap, all along the anode wire where you may have an insulation break, around the HV cage where wires come through the metal cage, the focus assembly, etc.

There are two different places that I remove the focus wire. You only need to do one, and that's only if you want to get the HV unit separated from the main chassis.

1- the focus wire attaches to the focus assembly at a solder joint covered by a rubber boot.

2- the other end is soldered to a tab on the tube socket. A small plastic cover pops off when pried by a small screwdriver to reveal the joint.

Kerry
 
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