G07 question

Bonecollektor

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This is my first monitor fix and I have a question: What are the two white wires that connect to the round studs directly below the F902? They are soldered to what looks like a large resistor but, like I said. This is my first fix so I'm still learning.

Here's a link to a pic (look below the call out for F902):

http://i414.photobucket.com/albums/pp224/Bonecollektor/g07s_08.jpg

Thanks.
 
That is the degauss coil that runs around the tube.
Each white wire plugs into one of those posts, doesn't matter which one.
 
Ok....I understand what a degauss cable is used for but, I didn't think it held a charge. The reason i ask is because after discharging the monitor (several times to make sure) everything was going smooth until I removed these cables. One of them landed on a ground prong on the frame and the prong touched the metal inside the insulated terminal and let off a big bang almost like a fire cracker had went off. Unless it was something else and it just happened to occur during the same period of time. But what could it be?
 
If you small fuse is blown and you are attempting to fix this model, the filter cap will not discharge when powered off (like it does when the chassis works). If you connect the opposite sides of the filter cap circuit, you'll get a real big bang as it discharges.

This is why the experienced techs always recommend discharging the filter cap before attempting repair. The best (and quietest) way is with a lightbulb....
 
I thought I checked the fuses....hmmm. Anyway, what's the light bulb thing?

you can use a socketed 100 watt electric light bulb and touch the two wires coming out from the light bulb on the leads of the capacitor. This method had been used by many electronic repairers around the world for the light bulb will act as an indicator to see if the capacitor still holds the charge. If there is a charge the light bulb will light and after discharged the light bulb will goes off.
 
That's what I though you were going to say. Neat trick. I remember checking the fuse for continuity and it was reading fine. Was I getting a false positive because I was reading through something else? Is it just safer to go ahead and discharge this cap every time just to make sure? Sorry for all the questions, this is all completely new to me. I've been searching the forums but haven't found really any tutorials just a lot of random info. Thanks for the quick replies! I appreciate it!
 
There are two fuses on a G07. One B+ fuse and one line fuse. When the flyback fails, it blows the horizontal output transistor and takes out the B+ fuse. The B+ circuit (which contains that large capacitor) is usually discharged automatically through a bleeder resistor, but if the fuse is blown, the circuit is not complete and the capacitor won't discharge. So, if you've plugged the monitor in recently, the cap will be charged - and has had no way to discharge.

Monitors contain very high voltages - always be wary of what you're doing. Things like this won't kill you, but it sure will hurt like hell.

-Ian
 
So my question remains: is there really no way to check this fuse without pulling it off the board? Do you check it with voltage applied? Is it best to just use the "light bulb" trick after doing the discharge and then pull the fuse off the board and check it? I understand the circuit but, I'm just trying to get the best troubleshooting/repair methods down. :)
 
Clean the glass of the fuse and eyeball it. Often you can see if its blown or not. Sometimes yes, sometimes no.

If the main filter cap was charged then the small fuse is almost certainly blown. I'd just assume that it is and move from there.
 
hey bud i just wanted to let ya know if you have any newbie questions dont hesitate to ask. My first monitor repair was on a G07 as well. And i bought the deluxe repair kit from bob roberts and went from there. A few tips and problems i ran in to>>

1. Be careful if you replace the flyback. It takes a good while to suck out all that solder around where its soldered in. And you dont want to pull on the flyback too hard cause it could rip the traces out of the board (the light green stuff) Then you have more problems. Take it slow and also make sure you put the caps in correctly. (positive legs on caps are longer)

2. Broken Solder joints. This is a big thing with G07 chassis. The solder either gets cold or breaks and then even though you replace all the parts there's still problems with it. ( i ended up replacing all the components on my first G07 and then still had to send it away for repairs to Peale and come to find out it was just a simple fix. The solder joints needed reheated up so they made a better connection in circuit. And in important parts its good to suck out the old solder and replace with new solder.

3. I found getting some tuning spray and blasting on the h sync and v sync pots made them work way better and take hold better.

4. Be careful messing with the B+. I blew my HOT by having the B+ cranked to full blast by accident and letting thepower on. make sure to learn how to test the B+ and make sure its in check after your repairs. I believe you put your positve lead on the big white ceramic resistor to the left of the chassis (when viewing from behind it). and black lead on the frame (gnd) should get a 120 Volts DC.

Any more ?'s feel free to ask. Im still a newbie myself but sometimes its easier to hear advice from newbies than it is experts lol. i like dummy terms myself. :) But there are many many many arcade gurus here to help.
-Mark
 
well my deluxe cap kit shows up today along with some other goodies I ordered. I picked up some more desolder wick and was planning on doing the solder joints over again just to make sure. So it's nice to hear that this is a good practice. Honestly, I was thinking of swiping the soldering station from work and using that sucker. It has the built in desoldering station and all the goodies! :D Wish me luck. I'll keep this updated and let everyone know if I have any further problems. Thanks for all the help everyone it's much appreciated!
 
Ummm, don't forget to remove the 2 screws on the side of the chassis that hold the flyback onto the chassis. I know somebody who has repaired about 30 of these chassis and forgot to undo those screws once. Boy did he feel foolish.
 
Ummm, don't forget to remove the 2 screws on the side of the chassis that hold the flyback onto the chassis. I know somebody who has repaired about 30 of these chassis and forgot to undo those screws once. Boy did he feel foolish.

YES! Good point there too!

Check bob roberts site for other tips as well.
 
Well the cap kit came in and I'm still busted. I've been following the flow chart and it looks like i might have a bad X501. i took it off the board and tested it with my meter and it's not looking good. I'm going to take it to work and check it with a more reliable meter. more than likely I will have to buy the IC501 chips as well. :(

Here's the flow:
1. Blank screen --> yes
2. F901 ok --> yes
3. F902 ok --> yes
4. Check voltage at R1 --> +167VDC
5. Remove X701 --> voltage still too high
6. No cracks or problems with solder
7. check voltage at metal case of X01 --> +167VDC
8. test X501, T501 & swap IC501 --> this is where I'm at now.

Does anyone else know of anything I could check? Should I try adjusting the pot for the B+ voltage or is it not going to help at this point? I would like to order the parts but it looks like X501 from MCM isn't available until June 22. :(
 
I replaced the R908 just to be safe. I don't think I've looked at the 900 series transistors yet. I'm going to do some more work on it tonight.
 
That fusible resistor has gotten me a couple times. Anyone have a source for them like digikey? I normally have plenty of parts chassis around to steal stuff off but eventually they are getting fixed so the parts need to be replaced.
 
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