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Once again I am playing with an IC I dug out of an old piece of equipment. Today it is the Texas Instrument TL 494 Pulse-Width-Modulation Control Circuit. The Data Sheet:   http://www.farnell.com/datasheets/1962656.pdf   which indicates that it was originally designed cerca 1983 but it remains relevant as Newark Electrons continues to supply it.   http://www.newark.com/texas-instruments/tl494cn/voltage-mode-pwm-controller-40v/dp/60K6995   The TL 494 has everything needed ...
Today I salvaged out a circuit board from an ESPE Dental Cure light. To my delight there was Kelvin precision resistor on the board. Specifically it was an Isotek PBV R033 which is a heat sink mounted 10 Watt Kelvin resistor with a value of 0.033 Ohms 1%. Here are front and back photos of the device. I first learned about these resistors a couple years ago from one of the great tutorials posted by peteroakes on building power supplies.       Now in the big scheme of things t ...
There are three components routinely used in the power input section of many linear and switching power supply that have confused me over the years and have often been difficult to identify. In this blog I would like to call your attention to them, show how they are used in the circuit, and give some tips on how to identify each of them. Since I am not an expert on any of these devices, comments, clarifications and corrections to this blog by my friends here on the forum who are the experts will ...
The other day while trouble shooting a control panel from a Pelton Crane Delta Q Dental Sterilizer I noticed that two of the required voltages were not being supplied by the main power supply but were instead being synthesized by a small group of components on one end of the circuit board. The display on the sterilizer was totally dark and the problem was going to be in one of 2 boards. The ultimate decision we faced was which of the two boards costing $1000. and $600 respectively was bad. Unfor ...