Monthly Archives: December 2005

UTP lightning protection schematics

First of all examine APC (American Power Conversion) LAN surge protector. It is removed from some APC UPS. The circuit is very simple. Diodes D1-D4 and D6-D9 are IN4006. The D5 diode is more interesting. It is 1.5KE6.8CA. This is … Continue reading

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DVD/DivX player on MTK1389

If you want to build DVD/MP3/DivX/Xvid and etc. player you need only to design box. Take cheap power supply for +-12, 5 and 3.3V any DVD reading hardware and simple mainboard based on MTK1389 chip. Order MediaTek firmware and enter … Continue reading

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Irwin Unibit drill

For drilling wide holes in thin sheet metal I bought Irwin Unibit drill bit. It is self-starting drill. For testing purposes I used steel sheet from ATX power supply box. Starting hole is a bit angular, next sizes are quite … Continue reading

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Thermocontrolled Fan, ver 3

In previous circuit, the temperature turn on the fan instantly. The regulation period is very short. To make it more wide just add only one resistor (R5): While adjusting sensitivity of your schematics use potentiometer instead of R5. It must … Continue reading

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Thermocontrolled Fan, ver 2

This small modification in the older schematics made it sensible to temperature. Main difference from older circuit is that I used one of error comparators for NTC thermoresistor. R3 and R4 must be equal or something near to make temperature … Continue reading

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PWM Fan control

It is simplest PWM fan speed control circuit from scrap. The detail values are not very critical. Here is the schematics: R1-~10K, R2-~100K, C1- 0.01μF, chip- TL494, KA7500. It would be good practice to put some electrolytic capacitor between Vcc … Continue reading

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Values of the capacitors

In every schematic you can find few capacitors. Sometimes you remove old caps from some junk boards. And sometimes it is difficult to determine the cap value. There is some standards for cap coding, but not every manufacturer take care … Continue reading

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More tubes

As I wrote in other article, we received some old Japanese made old hardware. On Friday I opened some big device and removed few more lamps. This was power supply. And one heavy used and another quite new 6AS7. Also … Continue reading

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