If you're talking the variable resistors (not variable capacitors---e.g. coils), the small white/cloudy clear ones on the back end of the board.. Then, they're fairly easy to replace.
Basically, you'll need a good 30-35 watt soldering iron with a good clean tip. The $4 ones in your dollar store might work for this project, though they tend to burn out the tips quite fast, so a better soldering iron with replacable tips and variable wattage might work better.
Invest in a solder sucker.. About $5 ?? From radioshack. A red squeeze bulb with a high-temp nylon nozzle (to keep it from melting). You want this to remove the solder from the old ones before you try to remove them (otherwise, if you try to "wiggle out" the old ones while holding the iron there, you will end up either burning yourself or breaking a wire trace on the board, and have to fix more stuff later.
No, you will not have to discharge the monitor. You can to be safe, but you don't have to. If you've never worked on these before, I would HIGHLY suggest you do it.
Also, on the G07's especially, that huge electrolytic capacitor (adjacent to the 2 fuses) can hold quite a punch in it. The electronics SHOULD discharge it when it's turned off, but it wont if something is wrong OR one of the two fuses blows. You can get quite the zap from the board even if disconnected from the tube unless you ensure that capacitor is discharged.
To remove, if you want to for some reason keep the old pots without wrecking them more, then heat each of the 3 leads comming out of them, then sucking off the solder on each one, then move to the next (from the bottom). Eventually it should be free or near free of solder. Then pull it out. Not everyone can desolder quite the same so you might have to heat up one or more of the leads really quickly to be able to GENTLY slide it out. Don't work too hard and NEVER press back down from the top thru the bottom without the solder being hot... you will rip the trace from the bottom of the board and have more problems fixing that with a wire jumper later.
If you DONT care about saving the old pot bases, then to make desoldering easier, take an old nail cliper, and cut off the lead as far off the TOP of the board as possible (as close to the bottom of the pot as you can). Clip off all 3 and the pot will fall off leaving 3 leads sticking up from the board. This then lets you remove them much easier, no need to rock out 3 partially soldered leads at once.. just pull each one out with a needle nose plier after removing the solder from them.
Once removed, ensure you can see thru each of the 3 holes, and press in the new pot gently. If it meets resistance, you may not have got all the solder out of the hole. If it's only one hole, heat it up and press it thru while the solder is warm. If more than one, you'll need to try to remove more solder. (A larger needle, pressed thru the bottom towards the top can help "spread" the cold solder enough in most cases. Again never press from the top down as you'll rip the trace off)
Once seated, heat each of the 3 leads and use new electronics grade solder, flowing enough around the lead and trace. Remember: 1st rule of soldering. Heat the metal, NOT the solder. Otherwise you will end up with "cold solder joints" where through a bit of vibration the solder will separate from the metal and/or trace, and then cause intermittent problems and have to be reflowed. Dont heat the leads too long, as you might end up melting the plastic disc on top or something, and when flowing the new solder, press the solder against the heated lead...NOT the iron's tip.
Make sure you match the OHM resistance of each pot... They may not be all the same. (I've never replaced them on a G07 myself).. Putting the wrong one in will result in very very bad control over the screen, or worst, frying some component due to too much resistance.
To double check.. Get an OHM meter, and set it on the 20Kohm or 200Kohm setting or so. Using the OLD pot from the board, touch the black lead to the left most post, and the right lead to the right most post (skipping the middle post). Note the resistance. (Make sure you have fresh batteries in your meter too, otherwise it might read wrong). Now compare that against the new one you're going to put in. Ensure it's the same or within reason.
E.g. If the old one showed 4.6 Kiloohms resistance end to end, the replacement one should be the same or can be SLIGHTLY more (e.g. 5.0, 7.0). Dont go less, other than by some small .0Kohm (e.g. 4.5 might work, 2.0 likely wont). The reason is, if you go less, then you restrict the amount of resitance you can set, and you may find you can't adjust the screen "as tall" as it once was. The reason you dont want to go to high is that you now lessen the "exactness" you can adjust. Getting one that is twice as much will result in you turning it half as much to adjust it, and trying to find the "sweet spot" might end up with you jumping from "too small" to "too much"... Pretty simple.. Think of a volume control only having 10 positions, or 5 positions. 10 is MUCH finer control!
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