Help me take my G08 apart

demogo

Well-known member

Donor 14 years: 2012-2025
Joined
Jun 30, 2007
Messages
14,951
Reaction score
2,102
Location
Texas
So I recently lost deflection on the bottom half of my G08 screen. (Bottom half of the screen is now scrunched up into a horizontal line).

Anyway, there's someone here on KLOV willing to help me out and look at my chassis and has asked for the following things to be boxed up:

The deflection board
The transistor assembly
The input protection board

Of all the monitors on my games this is the only one that I'm leery of and I don't have any idea of which pieces parts are which.

Can someone please walk me through the steps for taking out the required components without frying anything or myself?

I've included some pictures I just snapped below to make things easier:

attachment.php



attachment.php


I have more pics if that will help.

Thanks in advance!
 

Attachments

  • DSCF3283 (Small).JPG
    DSCF3283 (Small).JPG
    77 KB · Views: 183
  • DSCF3284 (Small).JPG
    DSCF3284 (Small).JPG
    75.3 KB · Views: 185
Hi;
It's not as tough as it looks but you will need to desolder a lead going to the focus assembly on the HV PCB, (left side of monitor frame while looking at the NECK PCB).

The INPUT PROTECTION PCB is the little rectangular PCB mounted on the cross rail that connects the left and right sides of the monitor frame, this is the board that accepts the input signals from the game board, should be 2 screws. Don't loose the little rubber spacers that go inbetween the board and the metal rail, these are necessary to prevent a short.

Then remove the metal cross member as well, unplug the neck PCB to make it a bit easer.

The DEFLECTION TRANSISTORS are inclosed in the metal heatsink assembly which is attached to the right side of the monitor and has the small fan attached, which is facing you when you are behind the display. Unplug the 2 molex connectors that lead from the heatsink assembly from the DEFLECTION PCB. Unplug the fan power connection from the DEFLECTION PCB as well, then remove the 4 screws that attach the heatsink assembly from the monitor frame.

Now all that is left is to remove the DEFLECTION PCB. You should already have the NECK PCB unplugged from the back of the CRT. Unplug the molex connector from the top of the HV PCB. Unplug the YOKE CONNECTOR, DEGAUSSING COIL and the DAG connection from the DEFLECTION PCB. Desolder the wire connecting to the FOCUS ASSEMBLY, remove the 2 screws retaining the DEFLECTION PCB and you should now be able to remove the board.

I am doing this from memory so if there are any problems, or if I missed anything, please let me know.

I hope this helps........
Jeff
 
Last edited:
Jeff, thanks -- will look the monitor guts over tomorrow with your notes and see how many more questions this brings up for me. :)

I assume I should discharge it in the standard way, one wire under the anode cup and the other hooked up to the monitor frame?

And is it just me, or isn't it a little crazy to have to desolder things while they're still in the cabinet?
 
Hi Demogo my 2 cents for yer G8 problem

hi demogo,

i have a little experience with this monitor..as i at one time owned a Sega star trek SOS as you do...and from that i remember yes you can discharge the second anode to the chassis frame...also as a side note for you...that heatsink with the transistors on it the transistors were supposed to be on the OUTSIDE..but i also think that is user preference...but also watch for the Standing transistors on the main chassis board ( the copper traces tended to break and the transistors always needed better heatsinks that were Isolated from the board if i recall...this is from memory so ANYONE feel free to Correct me :)... i always had Issues with my Electrohome monitor till i got all the board bugs worked out ...dunno if that helps but a good inspection of the trace side tends to reveal things ya hadn't notied before ;)

Super Good Luck..hope that helps !

Daniel.
VoicesInTheWind.
 
Last edited:
hi demogo,

i have a little experience with this monitor..as i at one time owned a Sega star trek SOS as you do...and from that i remember yes you can discharge the second anode to the chassis frame...also as a side note for you...that heatsink with the transistors on it the transistors were supposed to be on the OUTSIDE..but i also think that is user preference...but also watch for the Standing transistors on the main chassis board ( the copper traces tended to break and the transistors always needed better heatsinks that were Isolated from the board if i recall...this is from memory so ANYONE feel free to Correct me :)... i always had Issues with my Electrohome monitor till i got all the board bugs worked out ...dunno if that helps but a good inspection of the trace side tends to reveal things ya hadn't notied before ;)

Super Good Luck..hope that helps !

Daniel.
VoicesInTheWind.
Hey Demogo...after my last post i started thinking about the monitor issue a little more and went internet Digging...lol...i dunno if this will help but the info in it sounded great and i'm thinking it might help....BTW to anyone including admins...i don't know if posting a URL is wrong ..if it is i Apoligize...i'm only trying to help ..and if i'm wrong please inform me...thank you.... try this Demogo...it MIGHT help ya ..

http://www.biltronix.com/pdf_files/Simple_Sega_G80_Vector_Mods.pdf


Daniel.
VoicesInTheWind.
 
Hi;
There is a certain way to discharge the CRT, you cannot just ground the annode to the frame.. I fabricated a tool that uses 10 - 100k ohm resistors in series to ground the CRT annode and prevent damage to any components. Do some Googling and research this before you zap something.

It would be much easier to work on the monitor if it is removed from the cab.

Regarding the deflection transistors, some people (including myself) believe the transistors run cooler if the cooling air is blowing directly over them, hence the installation with the "bottle caps" inside the heatsink assembly as opposed to the factory exterior install.

Jeff
 
You almost certainly have to pull the monitor from the cabinet before you try to pull the parts off of it.

This will make unsoldering the focus wire much easier. Unsoldering it isn't strictly necessary, but it makes it easier to handle the separate parts and prevents it from ripping something off during shipping.

To remove the monitor from the cabinet, unplug the video connector, the power connector, and possibly a ground braid from the back of the monitor.
Open your control panel to see the front of the monitor.
The cardboard monitor surround is attached to a wooden frame that pulls out.
There is a square wooden sheet that the monitor frame is bolted to. You want to leave that attached to the monitor, but remove a few screws that hold it to the cabinet.

Then, the wooden sheet can be pulled straight out from the front of the cabinet. It has cut-away sections to provide hand holds. Watch out for snagging the frame on any wires.

Careful not to break your tube.

With the monitor out of the game, you can access the screws that hold the power transistor assembly and the heat sink to the frame. I can't imagine how anyone could remove them while inside the game.

If you want to do some troubleshooting, you could swap the two connectors for the power transistors before you remove everything. If your 'missing' half of the screen moves from top/bottom to left/right, then all you may need is some replacement output transistors. You could probably handle that repair on your own for about $20. Otherwise, $20 is roughly the cost of shipping one way.

I'd try that first.

Kerry
 
I knew i forgot something else

Jeff...your right...it was late last nite and i forgot to add what you said about grounding the anode...KUDOs for you sir :)

Thank You for that..

Kerry... GOOD INFO...yer right about that :)

Kudos as well !


i'm getting slow in my young age...LOL


Daniel
 
Guys, thanks.

I'll give this a shot.

Every time I've discharged a monitor in the past I've always just grounded it to the frame and never had any issues but this monitor scares me so if there's a better way then I'll do it. I vaguely recall someone hooking it up to a 100w light bulb or something like that.
 
OK, had some help from folks here (big thanks to smalltownguy2) and was pointed to a thread that says it's really bad to discharge vector monitors directly to the frame:

http://forums.arcade-museum.com/showthread.php?t=57544&highlight=discharging+go5

Apparently chaining 10 of these resistors together in the discharge path knocks the discharge down to safe levels for the monitor.

http://www.radioshack.com/product/index.jsp?productId=2062334&filterName=Type&filterValue=1%26amp%3Bamp%3B%23047%3B2-watt+resistors

It's all of $2.50 in parts as well so it'll become a standard part of my anode discharging from now on.

Got the resistors; tomorrow I'll solder them all together.
 
Last edited:
You almost certainly have to pull the monitor from the cabinet before you try to pull the parts off of it.

This will make unsoldering the focus wire much easier. Unsoldering it isn't strictly necessary, but it makes it easier to handle the separate parts and prevents it from ripping something off during shipping.

To remove the monitor from the cabinet, unplug the video connector, the power connector, and possibly a ground braid from the back of the monitor.
Open your control panel to see the front of the monitor.
The cardboard monitor surround is attached to a wooden frame that pulls out.
There is a square wooden sheet that the monitor frame is bolted to. You want to leave that attached to the monitor, but remove a few screws that hold it to the cabinet.

Then, the wooden sheet can be pulled straight out from the front of the cabinet. It has cut-away sections to provide hand holds. Watch out for snagging the frame on any wires.

Careful not to break your tube.

With the monitor out of the game, you can access the screws that hold the power transistor assembly and the heat sink to the frame. I can't imagine how anyone could remove them while inside the game.

If you want to do some troubleshooting, you could swap the two connectors for the power transistors before you remove everything. If your 'missing' half of the screen moves from top/bottom to left/right, then all you may need is some replacement output transistors. You could probably handle that repair on your own for about $20. Otherwise, $20 is roughly the cost of shipping one way.

I'd try that first.

Kerry

> If you want to do some troubleshooting, you could swap the two connectors for the power transistors before you remove everything.

OK, for the sake of clarity, you mean the molex connectors for the deflection transistors? So swap these, circled in the picture below?

Also, should I discharge the monitor before doing any of this?

attachment.php
 

Attachments

  • DSCF3284 - Copy (Small).JPG
    DSCF3284 - Copy (Small).JPG
    75.5 KB · Views: 75
Finally took this beastie out of the cab tonight.

Tomorrow I'll start messing with it when I have more time.

In the meantime, I had to cut the cabinet groundwire to the monitor frame to remove the monitor and I'd like to re-attach it. I'm sure this will not be the last time I have the monitor out.

I could just crimp the cut wires together but would a quick disconnect work too as that would mean I wouldn't have to cut and crimp every time I take out and put the monitor in.

Thoughts?
 
Back
Top Bottom