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  1. Miguel Lopez

    Uploading Image problems

    Well, ir seems that I can access the website that you gave me. Usually I can not access file hosting websites, cause I'm not allowed to do so by my webmaster. Thanks Ian and Kris. Ian, I think I can go on with the thread. Anyway, I'll wait until you have moved the picture-related posts to...
  2. Miguel Lopez

    Uploading Image problems

    Sorry no results. Without pictures, this thread should be closed and deleted, cause it is empty words only. Sorry again. It should be one of the lots of restrictions that I have. Thank you very much for help.
  3. Miguel Lopez

    Uploading Image problems

    Hi Kris I did that. The problem is that when I click on the picture, the program begins to upload it, and then inmediately, the following error message appears: The following error occurred There was a problem uploading your file. <filename> And nothing else. I'm not sure what the error is...
  4. Miguel Lopez

    Uploading Image problems

    I found that I don't know how to upload pictures now. :( Can you explain me how to do that, please? ;) Thank in advance
  5. Miguel Lopez

    Home made valve oscilloscope. Version 2.0

    Hello everybody A couple of years ago, I began to build an oscilloscope from scratch. I had a Soviet C1-94, but the CRT failed, as well as several parts of the circuit that I had to repair from time to time. Finally the C1-94 got out of service and i wasn't able to fix it, mainly due to the CRT...
  6. Miguel Lopez

    Capacitance between two wires

    If you need to calculate the true value of capacitance, I have no idea. But if you need to know if the capacitance would be high, I can tell you the in the college we used a mnemonic in which a pair of twisted wires would have about 2pF/cm. So, in your case, I think the capacitance will be...
  7. Miguel Lopez

    Constant current power supply

    I think that a continous current adjustment won't be required (just my humble opinion). A step-selector will do the job at the exact value of the several required current. Fixed resistors can be selected to stand high power dissipation. This way, an ammeter is not needed.
  8. Miguel Lopez

    Constant current power supply

    Use a 7805 or an LM317 with a variable resistance between output and adjustment pins. Take output from the adjustment pin. This will provide a useful and simple constant current source. Surely you will need a TO-3 to stand 0-5A, and a big heatsink.
  9. Miguel Lopez

    Help with synchro sawtooth generator

    Thanks for your comments. I mounted the circuit on the breadboard, using BC546 transistors and it worked too, but I noticed a non-predicted behaviour. It gets synchronized with the signal up to 15-18kHz (red trace pulses get narrower as the frequency increases), then the pulses (red trace on...
  10. Miguel Lopez

    Help with synchro sawtooth generator

    Simulated with 2N3904 NPN transistors. It works!!!! Now to make test on the protoboard. In the oscillogram it is in red the output of the synchro oscillator and in orange the synch pulses using an RC network ****************************************************************** Is the word...
  11. Miguel Lopez

    Help with synchro sawtooth generator

    I tried with N-JFETs on the simulator and it didn't worked. Maybe I have try iy in the protoboard with both nJFETs and NPN BJTs. Negative. That circuit just provide pulses to trigger the sawtooth generator which in my case is a Miller timebase generator called "Phantastron" or something like...
  12. Miguel Lopez

    1.2 V Power Supply Voltage drop

    The LM317 will supply 1,25V with (I guess) enough current capability to drive the circuit.
  13. Miguel Lopez

    Help with synchro sawtooth generator

    Thank you Arouse1973. Well, I need an oscillator capable to work both in free running and synchro mode at the same time. When I built my valve oscilloscope, used the circuit shown in the attachment. That circuit, if there is no signal applied from any of the Y-plates (or there is a DC...
  14. Miguel Lopez

    Help with synchro sawtooth generator

    Hello all I'm trying to design a sawtooth generator circuit capable of free running and synchro operation. The purpose is to built a transistor scope in the future to replace my homebrew valve oscilloscope. I have designed a circuit capable of synchro operation and I have tested in the...
  15. Miguel Lopez

    Problem with P2015 HP printer.

    Not sure what you mean. How can I do that?
  16. Miguel Lopez

    Problem with P2015 HP printer.

    Hello I have a P2015 Hewlett-Packard printer at the office that is presenting a problem. When it takes the paper from the bottom tray, it prints the page you ordered, and then it takes another sheet of paper and pass it throught the printer leaving it blank. It does that with every single...
  17. Miguel Lopez

    Suggestions for a new oscilloscope (looking)

    Don't buy any. Build one on your own. :)
  18. Miguel Lopez

    Voltage to current amplifier

    That's right. Very useful in instrumentation, where a 4-20mA loop is used.
  19. Miguel Lopez

    Voltage to current amplifier

    The output of this kind of amplifier is a constant current, which depends only on the input voltage, not on the load (between certain limits). You can vary the load, and the current will be constant.
  20. Miguel Lopez

    Transistor Resistor Help please

    He can connect the LEDs in parallel. With such transistor, there will be no problem with the current increase.
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