REPAIRING AND NOT THROWING AWAY

REPAIRING AND NOT THROWING AWAY

Richtige Fernseher haben Röhren!

Richtige Fernseher haben Röhren!

In Brief: On this site you will find pictures and technical information about Service Modes, Circuit Diagrams, Firmware Update procedure, Disassemble procedure, Universal remote control set-up codes, Troubleshooting and more....

If you go into the profession, you will obtain or have access to a variety of tech tips databases HERE IT IS Master Electronics Repair !.

These are an excellent investment where the saying: 'time-is-money' rules. However, to learn, you need to develop a general troubleshooting approach - a logical, methodical, method of narrowing down the problem. A tech tip database might suggest: 'Replace C536' for a particular symptom. This is good advice for a specific problem on one model. However, what you really want to understand is why C536 was the cause and how to pinpoint the culprit in general even if you don't have a service manual or schematic and your tech tip database doesn't have an entry for your sick TV or VCR.

While schematics are nice, you won't always have them or be able to justify the purchase for a one-of repair. Therefore, in many cases, some reverse engineering will be necessary. The time will be well spent since even if you don't see another instance of the same model in your entire lifetime, you will have learned something in the process that can be applied to other equipment problems.
As always, when you get stuck, checking out a tech-tips database may quickly identify your problem and solution.In that case, you can greatly simplify your troubleshooting or at least confirm a diagnosis before ordering parts.

Happy repairing!
Today, the West is headed for the abyss. For the ultimate fate of our disposable society is for that society itself to be disposed of. And this will happen sooner, rather than later.

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..............The bitterness of poor quality is remembered long after the sweetness of todays funny gadgets low price has faded from memory........ . . . . . .....
Don't forget the past, the end of the world is upon us! Pretty soon it will all turn to dust!

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All posts are presented here for informative, historical and educative purposes as applicable within fair use. NOTHING HERE IS FOR SALE !

Monday, 24 February 2020

USB MULTIMETER POWER SUPPLY

Typically, the multimeter is powered by a nine-volt battery type "Krona". It is inexpensive, but it ends abruptly. Moreover, now almost everyone has a device powered by a USB port - laptops, tablets, smartphones, and the corresponding chargers. Here is a description of the voltage converter unit to power the multimeter from any USB port or from a charger with a USB connector. The task of this unit is to increase the voltage 5V, available on the USB-connector, to a voltage of 9V, necessary to power the multimeter.
The figure shows a diagram of a simple unit that allows you to get a stable DC voltage of 9V from the USB port, provided that the load current does not exceed 150 mA. Using such an adapter, it is possible to power not only a multimeter from a USB port, but also other circuits and devices powered by Krona.
The circuit is based on a DC-DC converter on the LM3578AM chip. Since the converter is pulsed, an inductance L1 is installed at the input, which prevents the penetration of pulsed noise into the circuit of the device, the USB port of which serves as a power source. As part of the A1 chips, there is a pulse generator with PWM, and an output key. The key goes to conclusions 6 and 5. Pin 7 is the input of the control protection circuit, which determines the current through the key by the value of the voltage drop across the resistance of the resistors R2-R4. And when it exceeds the permissible value, protection is triggered.

Voltage is pumped at inductance L2. Then, this alternating voltage is rectified by the Schottky diode VD1 and smoothed by capacitors C6 and C7. The output voltage is stabilized by comparing the voltage removed from the R5-R6 divider with the reference voltage generated by the stabilizer, which is part of the microcircuit. The control input is terminal 1. Resistors R5 and R6 form a voltage divider, with which the output voltage is divided so that with the required output voltage of 9V, terminal 1 A1 has a voltage of 1V.
The output voltage is greater, the greater the division ratio of the divider R5-R6. In principle, the maximum output voltage can be made much higher (but not more than 30V). You can increase the output voltage by decreasing the resistance R6 or increasing the resistance R5.
Mounting the converter is most conveniently done on a small printed breadboard.
Chokes L1 and L2 - finished, industrial production.
Conventional resistors have a significant variation in resistance, so if the output voltage is less than 8V or more than 9.5V, you need to choose R5 or R6.
Author: Zhurbin A

Posted By: FRANK at 08:19
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