Everyone who has been repairing electronic equipment knows that sometimes it is necessary to determine its value by the appearance of a resistor. The easiest way is to measure the resistance with an ohmmeter, but the trouble is, it is not always possible to solder it without damaging the circuit board, especially the multilayer one, but it happens that there are doubts about the integrity of the internal contacts. If there is a circuit, everything is simple - you can look into it and see that R18 is, for example, 47 ohms. And if it is not there, but you need to figure it out, and you will have to draw the scheme yourself?
Fortunately, manufacturers of electronic components have agreed among themselves, and there is a standard marking of resistors. True, and it has changed over the past decades.
The color marking of resistors is the most common nowadays. It is very simple, and reading the denomination, holding a simple cardboard decoder in your hands, is a matter of seconds. This device is widely available, available in any radio store and is very cheap, so it is not worth remembering the color values. The marking of resistors consists in the fact that rings of different colors are painted on the resistance,each of which means a digit, a multiplier, or a degree of precision.
Strips available from three to five. They should be read from the first, located closer to one of the conclusions. For example, there are four lanes. The first is brown, the second is black, the third is red, the fourth is grey. You should dial these colors on the decoder, skipping the third one (there you should select the “no” position). Done, that's 1 kΩ with an accuracy of 0.05%. If there are three bars, the accuracy is 20%.
Sometimes there is a need to deal with old Soviet equipment that is still in use. Once she was scolded, she seemed clumsy and ugly, but time has shown the amazing vitality of some samples of this equipment, and now it is even sometimes called "vintage". The marking of Soviet-made resistors is even simpler than color, the value is simply written on them, for example, 4K7 means 4,700 ohms. And that's it. Simple and clear. One drawback - this inscription may be at the bottom, Soviet radio factories very rarely used "standing" mounting of resistances, the Japanese loved it to save space on the board.
The miniaturization of electronic technology has put its manufacturers in front of the need to invent new ways of mounting. The classic soldering of resistors through the holes on the board in a “standing” or “lying” position takes up too much space, and now a new way to assemble microcircuits has appeared - smd. In this English abbreviation, three words are encrypted: “surface” - surface, “mount” - installation, and “technology” - this is clear what it means. smallparts are soldered directly to the track on the surface, without holes and legs. The resistors needed to be re-labeled, and other components such as diodes and capacitors too.
Marking smd resistors is somewhat reminiscent of the good old Soviet way. They also have numbers and letters printed on them. There is still a difference. The letter is not always present, if necessary, "R" is used as a separating comma.
For example, 2183 means that 218 needs to be multiplied by 1000 to get 218 kΩ. Resistances with a tolerance of up to 10% are marked with four digits, the last one means the power to which you need to raise the ten, and multiply the three-digit number formed by the first two digits by this result.
Slightly harder with higher quality smd resistors, with 1% tolerance. Here, the degree of tens is given by the letter, for example, D is 10 cubed. If 10D is written on the resistance, it means 10 kOhm.
Besides the lookup tables, the repairman will need a magnifying glass as the characters are very small!
