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  1. (*steve*)

    One of my colleagues...

    I think I promised I would test a transistor using Ross's tester. This a BC547 that was lying on my bench The datasheet tells me that it has a hfe of between 110 and 800 with an Ic of 2mA and a Vce of 5V. Some datasheets go further and give ranges (or typical values) of hfe at other...
  2. (*steve*)

    For Sale: Silicon Chip magazines

    After filling in all the missing back issues in my collection of Silicon Chip magazines, I have a stack of issues to get rid of. Silicon Chip magazines 1989 Oct Nov 1990 Apr Sep 1991 Mar Nov Dec 1992 Feb May 1993 Jul 1994 Mar Sep 1995 Jan Mar May Jun Jul Dec 1996 Jul Nov Dec 1997 Jan Feb Mar*2...
  3. (*steve*)

    VFD (Variable Frequency Driver) for 3-phase motors.

    Aaaah, that makes more sense. Because that 120V isn't just one of the phases, it's some funny "half a phase" thing isn't it. Most new properties built here these days have underground power. This is delivered to a green "mushroom" that is placed close to a corner of the property near the...
  4. (*steve*)

    VFD (Variable Frequency Driver) for 3-phase motors.

    Really? I just asked and paid the money. But that was when the house was being built. As I recall, the major expense was several hundred dollars for the meter, and under $200 for the additional cable cost. They may have asked me why, but it was just curiousity.
  5. (*steve*)

    Create controlled 50v pulse

    A solution to this is to manually focus when the blade is not moving, then arrange a trigger to fire the flash when the blade is in that position. Typically you'll use an optical trigger that uses an infrared beam to detect the blade (positioned well out of shot). In a darkened room you set...
  6. (*steve*)

    One of my colleagues...

    Versatile Bipolar Transistor DC Beta Tester This device was a featured by Ross' family at his funeral. I think it was an excellent selection by them. They have recently passed it on to me and I thought it would be the next thing to show here. Clearly built to be versatile, this allows the...
  7. (*steve*)

    Possible PC motherboard failure?

    It could also be a power supply. Is it producing a power good signal?
  8. (*steve*)

    Will 13v led lamps run on 12v?

    The power supply, as others have suggested, is a constant current driver. Note the current is specified as "700mA(const)". I suspect the light fitting just contains three LEDs in series and that the input power marking referees to the transformer. If this is the case then you need one driver...
  9. (*steve*)

    Will 13v led lamps run on 12v?

    There are a couple of possibilities. The first is that the original power supply is a led driver that delivers a constant current. In this case, replacing it with a voltage source could result in the LEDs not lighting at all, it them immediately being destroyed. There may be a little leeway...
  10. (*steve*)

    Is anyone an expert in wafer fabrication?

    I question some of your assumptions. Wikipedia lists over 500 semiconductor fab labs in China.
  11. (*steve*)

    Power rating of WEL resistor

    What voltage is on the capacitors? Use the formula P = V*V/R to determine the actual dissipation. If the voltage is 25V, then the power dissipated is 25*25/100 Watts. That's 6.25W. in this case of use a 10W, or maybe even a 15W resistor. Always leave plenty of margin of you can. Also...
  12. (*steve*)

    Sony VCR blows fuse

    Do you have a multimeter? If so, I suspect that if you read the resistance across the pins of the power cord (obviously with it NOT plugged in to a power point) after replacing the fuse again, you'll find an almost dead short across them. There are a few relatively common and easy to repair...
  13. (*steve*)

    One of my colleagues...

    I've just measured the input vs zener current for a selection of zener voltages. The output capacitor is rated for 63V, so I used a string of zeners that added up to about this and measured as around 65V. I had a meter in series with the zeners, so the zener voltage read included the burden...
  14. (*steve*)

    G & E Bradley CT471C

    Thanks Edd, that makes it so much easier to read and understand.
  15. (*steve*)

    Dimming an over bright LED

    A voltage source provides a given voltage and the current is determined by the nature of the load. A current source provides a certain current and the voltage is determined by the load. Batteries seem like a voltage source, but if the load demands too much current, the voltage falls. The...
  16. (*steve*)

    Dimming an over bright LED

    If the led is being driven by a current source then a parallel resistance is the correct approach (unless you can modify the current setting).
  17. (*steve*)

    G & E Bradley CT471C

    Sorry, I thought you had replaced the transistors in the chopper. My first step would be to take the meter out of circuit and replace it with an equivalent resistor. That way you can leave the unit powered up for extended periods without writing about damaging the totally irreplaceable meet...
  18. (*steve*)

    One of my colleagues...

    A "Zener tester"/ This is one of the few odd bits of Ross' gear that has a label, but no instructions! The banana plugs fit into a meter, the crocodile clips obviously connect to the device under test, and the banana jacks on the left to a high voltage source??? And then press to test? If...
  19. (*steve*)

    Altec Lansing BX1121 Pinout

    Maybe they changed the colours of the wires? Are the colours in the same order at the other end of the cable?
  20. (*steve*)

    G & E Bradley CT471C

    I've just looked at the schematic again, and also had another read through the thread. Have you checked the two BAY31 diodes? A failure of either of these could damage the silicon transistors far more easily than to the original germanium devices (ge devices allowed reverse base emitter...
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