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Recent content by rfredel

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    Help to identify devices by photos

    Hello, the device in the first picture looks like an old VTM. I think it is DIY. The devives in picture 2 and 3 looks also DIY, because I can not see any logo . Device no. 4 is especially made for weatherforecast. Here in Germany it was built by Lambrecht GmbH...
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    Power Amplifier safety modifications.

    Hello, you can calculate the current by ohm' law. For the primary fuse use the mainvoltage in worst case (-5%). According to the soft start circuit, the 500 VA transformer needs I = P / U = 500 VA / 215 V = 2,32 A. Use 2,5 A very slow blow up or 3,15 A slow blow up Type. The 60 VA...
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    RGB to PAL video encoder with MC1377 works but no with everything...

    Hello Axxel, is it only a writing error, or do you use a 3,58MHz quartz? European Pal needs 4,43MHz, 3,58MHz is for NTSC. I think your TV will be Multi-Norm and so you get color. Regards Rainer
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    Accuracy of DVM is "+/-0.8% +1"...what does this mean.

    Hello treez, the accuracy means that you have + / - 0,8% of 400mV = + / - 3,2mV of the final value. So your final value of 400mV that is displayed can be 396,8mV - 400,0 - 403,2mV. Is it a digital meter it can be a reading of 399,9 - 400,0 - 400,1 about the ADC. That means + / - 1. I hope it's...
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    TTL waveshaping, RC networks

    Hello Danny, X means that the input can be high or low. Yes, thats right. Normal Gates and chips don't have schmitt trriggers. First I look for the specifications of the power supply and if the LOW and HIGH voltages of Input and output are OK. These specifications I wrote in post #7. The I...
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    TTL waveshaping, RC networks

    Hello Danny, I think, you don't know the real function of schmitt triggers. So I give you this link from TEXAS Instruments Also I give you a datasheet of a NAND gate with internal schmitt trigger If you have a gate, like a NAND gate with two inputs, you can see at the function table, that if...
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    TTL waveshaping, RC networks

    Hello danny, That's right. A schmitt trigger is a finish and cheap device, that also can use as normal gates (for example: SN 7413). An op amp needs more things around, but it's right that you can adjust the switching points and hysteresis. A finish schmitt trigger is easy to use and an op...
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    What is an "audio grade" electrolytic capacitor?

    Hello Brian, I agree with you, but I think we are to good and to honestly to sell Voodoo devices. :-D Regards Rainer
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    TTL waveshaping, RC networks

    Hello danny, All waveforms and switching events have slewrates. The slew rate is the time between 2 switching points. It's equal if you use non - inverting Schmitt triggers or inverting. That is dependent from the use. There is no difference. An Op amp can connected as a schmitt trigger. With...
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    What is an "audio grade" electrolytic capacitor?

    Hello treez, every good elektrolytic capacitor or normaly capacitor is "audio grade". Some "Audio gurus" think, that they can hear differences between capacitors. They say, this one have a better "sound" than the other. So they say this is "audio grade" and that not, but by measuring they can...
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    TTL waveshaping, RC networks

    Hello Danny, The slew rate must be high, to change quickly from low - level to high level or back. Slew rate is not an input source, it's the time from changing high to low or back. TTL and CMOS chips are digital chips. They only know low and high stages. The voltage between max. low - level...
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    OP-AMP Design with BJT

    Hello Abber, follow the link to my homepage and look at page 10 **broken link removed** I hope it helps. Regards Rainer
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    TTL waveshaping, RC networks

    Hello Danny, TTL devices have defined voltages for supply voltage and low and high level. VCC = 4,75V to 5,3V[/B] Input LOW = 0 to 0,8V Input High = >2V to VCC Output High = VCC to 2,4V Output Low = 0 to 0,4V CMOS devices have also defined voltages for low and high level, but they are...
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    TTL waveshaping, RC networks

    Hello Danny, the picture 1 shows a squarewave, but the probe of your scope is not correctly adjust. The capacitance of the probe cable is uncompensated. Look for your manual to adjust it correct. Picture 2 and 3 shows a sawtooth with the same frequency. You only use different horizontal...
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    [SOLVED] Relay switching AC inductive load

    Hello Tim, Zener diodes is not good, because if they break down, you have a short circuit. Better is to use a Varistor. Also look for your relay. Is the distance between the contacts great enough, to open it without an electric arc. The arc must be off, before the other contact is close. else...

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