Re: Clean and Lubricate Pots in Tek 475


Ed Breya
 

Yes, getting the pots out may be the hardest part, whether you refurbish them or replace them. Again, I don't know how accessible they are, but at least they're on the periphery of the front panel. If the pots are those square black or blue "modular" type, with screws on the back, they can easily be opened up for cleaning and re-lubing. Just keep track of all the pieces as you go, and how they need to fit back together. Some of these pot types are riveted together rather than held with screws. Even these can be worked over by carefully drilling out the ends of the rivets, and replacing them with 2-56 screws, long enough to go through the assembly.

If it is just too much grief to get the pots out, and soaking the bushings isn't enough, there other tricks to help with getting more oil into them. If you have a well stocked parts/junk department, you may have some "pot spacers," which are typically hollow hex tubes of various lengths, threaded the same as the pot (1/4-30 or 1/4-32 I think). These are commonly used in equipment to recess pots behind the front panel. If you find one, you can remove the original pot nut, and thread the spacer on in its place, just a little more than hand tight. Then put the scope on its back with the front panel up, and flood the spacer with oil and let it soak overnight. If this is still not enough, the next degree is to do vacuum assist, if you have any kind of vacuum source available. It just has be rigged up to put suction on the temporary oil reservoir that you made with the spacer. If you can get decent vacuum on it for maybe a few seconds to a minute, some air from inside the pot should bubble up through the oil, and then pull some more oil in after the vacuum is released. This can be repeated a number of times. The pots are not truly "sealed," and will gradually leak everywhere, so any pressure difference is only temporary.

If you don't have any pot spacer hardware, you can do the same with a piece of rubber or plastic tubing, but it's trickier to attach. You want a tight fit, so the tubing is deformed and self-threaded onto the pot, to minimize oil and air leakage.

An alternative to vacuum is to put air pressure on instead, to force some oil into the pot. As you can imagine though, this could get quite messy - especially if you have a blowout in the tubing attachments.

Ed

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