some explanations - long
Hi Brent,
A few answers to your questions:
2. When you spray anything other than air on the vanes of a tuning capacitor, they coat the vanes or fins. Tuning Capacitors are variable air capacitors where the insulating component between the vanes is the air itself and the vanes are the capacitor plates. As the plates are rotated, there is more or less surface area opposing each other which then varies the capacitance that the system sees.
But this assumes that air is the only insulating medium and that its consistent. Most tuners will accumulate a slight coating of dust on the vanes usually evenly distributed so commonly tuning doesn't get intermittent but the whole scale may be thrown off a little. Blowing the dust out with air can correct that. If you're braver than smart, one can try cleaning the vanes also with a q-tip and airdrying solvent. Anyway, if anything is sprayed on the vanes that leaves a residue (like oil or propellant), then the plates see the residue and air which will change the capacitance value which will make the tuner go way off. Or if the residue is unevenly coating the vanes, the capacitor will no longer be linear in its rate of change and the tuner will go way off. Either way, anything other than air between the vanes will screw up the tuner. Then you'll have to clean it carefully with pure IPA carefully. I think others here will tell you its a royal PITA!
A side explanation is tuner gangs means Ganged capacitors -more than one variable capacitor is hooked together on a common shaft so that all sections are moved together (like a chain gang working together). A rough estimate of tuner quality has to do with how many caps are ganged together - the typical for most analog receiver/tuners was 3 section gangs, best I've heard are 5 section gangs on TOTL units.
3. The term "pots" refers to the controls named potentiometers - devices to control voltage potential between two points (or more) in a circuit. They are also called sometimes variable resistors and can handle voltage at usually low current levels, say less than 0.5 amps. Most potentiometers are made from conductive carbon, conductive plastic, or fine wirewound resistive elements. Newer units are made from metal or carbon film elements laid down on a substrate with a wiper attached to the shaft.
Stepped attenuators are the same type of pot above with a mechanical device to provide stepped rotation instead of continuous rotation. This provides some repeatability in resistance value per rotation position. True precision stepped attenuators may be built from 24 position switch-like devices with discrete resistive elements between each position.
High power potentiometers that handle high current (>1 amp) are mostly wirewound elements on a large core to dissipate heat generated by the element. These are more commonly called rheostats (which I don't know the derivation of). Typical are analog light dimmers, Variacs (really high power and voltage), and heater control elements.
4. Typically, compressed air cans for me last about 1 per 3 units cleaned. But I can blow 1 can into 1 unit if its big, complicated, and very dirty. But for $3-5 dollars, what a difference it can make in appearance and function when the unit is properly cleaned.
5. Brushes - you're on the right track. I use common soft to firm haired paint brushes, with good sized handles. Buy an assortment from your local hardware/paint store ranging from 1/2" to 3 inch widths, will cover most anything you need to clean. An assortment of non-lint producing Q-tips or swabs and cleaning pads from an electronics parts store will help with those hard to reach spots. You just don't want to leave anything like lint or brush hairs behind if possible.
Hope this helps.
Regards,
Bart
