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sherbo's Achievements


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  1. Hello guys, I'm using the UA741 op-amp but theres a problem.. offset voltage ! I always get (saturated +ve output) until the inverting input (V-) is 1.8 volts greater than V+. Now 1.8V... isn't that ALOT ? Anyway, I tried using the offset null pins but they didn't work ! Here's what I did exactly: Pin 2 (V-) : GND Pin 3 (V+) : GND Pin 6 (Vo) : DMM Pin 1 (offset null) : 10k Pot beginning Pin 5 (offset null) : 10k Pot end Pot slider ---> GND Supply pins: +13v & GND. the opamp insists on giving +13V (sat.) regardless of the pot. setting. Does this mean a bad IC ?? I've tried 3 of them so far.. maybe the whole lot was bad ??
  2. Okay one final question. You said I should connect the stereo via an attenuator. Well the mixer circuit has the inputs connected to a pot & a resistor, isn't this enough ? Thanks & sorry for all the trouble :)
  3. My car stereo doesn't have any inputs. It only has an amplified output. I want to connect my mobile phone to the car speakers to emulate a (mobile car kit). Here is what I'm thinking right now: stereo (amplified) ----->Mixer ----> Speakers Mobile -------> Amp --->| Would this mixer work ?? http://www.electronics-lab.com/projects/audio/009/index.html I'm mainly worried about the sound quality deteriorating, with only one BJT the circuit seems too simple. Btw, are the component values critical ? I'm not sure if I'll find 5 uF caps, and I'm thinking of powering it directly from the car battery (with a cap to reduce noise). It's crucial to me that I take both AMPLIFIED signals then mix them. I want the circuit to act like a (black box) that I just plug into my speakers.
  4. Hi all, I need to connect this amplifier to my car speakers, which are also connected to a car stereo. That would lead to 2 amplifiers connected in parallel, giving different output signals. Do I risk damaging this amp and/or the stereo's internal amp ?? I mean will something really get burned ? If so, please suggest a *simple* way of connecting both at the same time. It doesnt matter with me if they can run together (mix) or if one of them gets priority over the other, just as long as all hardware is protected. The amp I'm referring to http://www.electronics-lab.com/projects/audio/006/index.html Thanks in advance :)
  5. Thanks audioguru for your great explanation :) It'll take me a few days to try it (exams), but I'll keep you informed.
  6. Audioguru: So what you're saying is the transistor is already damaged ?? Is this a common transistor fault ? btw, the 10A came from 2 transistors in parallel - I added a similar one with the base resistor and all. audioguru: So theoretically, should this circuit run fine under all loading conditions ?? If you give me a yes here I'll go and buy some replacement transistors (those things aren't cheap...) Another question (sorry I'm kinda new) I was trying to analyze the circuit, and wondered - is there a model for the 78XX regulators ?? Thanks for your time :)
  7. Hey guys, I'm trying to build a power supply for a car-based MP3 player (a stripped down computer). I've tried this link for the +5v rail, it gives very good current (upto 10A now) but there's one CRITICAL problem: when not loaded, the output voltage is 12V !! Just to make it clear, I'm using the 7805 regulator not the 12v ! (I'm stressing this because the description doesn't match the schematic) The link: http://www.mitedu.freeserve.co.uk/Circuits/Power/boosti.htm What do you think needs to be done ?? I know that linear supplies would waste alot of energy, but I can't build a switching PSU - they're too complex & the ICs aren't easily obtained from where I live. Thanks in advance for your help.. :)
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