aha okay, thanks 

Hi,
I've built this project in a wiring board and it works, so I'm studying the whole ciruit now... but i wonder what function the diode D1 together with R2 has 
And if i want to increase the frequency of the (piezo sounder and the LED), i can easily decrease the resistance (R3) or the capacitance (C1), right?

Thanks in advance

Thank you so much Audioguru for the help 
I'll ask again if i face a trouble ... 

Hello,
Can i use surface mounted capacitors instead of the two capacitors in this curcuit?
http://www.electronics-lab.com/projects/oscillators_timers/008/index.html
And what's the value of C2 ? is it nano, piko ...? and can i use a LED instead of the piezo sounder (just to indicate).

That part model (7447) in Multisim is known to be faulty over a few issues. Even in the latest release it is still not working. They never bothered to fix it. Use a 74HC4543 or 4543 to get it working

Thanks to inform me about the 7447, i didn't find 4543 in multisim so i used 4511 instead (but changed the display to "commen cathode" instead) and finally it's working now ... Thanks again

Hi Mukhalled,
I haven't used old TTL ICs for many years and I have lost my TTL Cookbook.
The datasheet for the 74LS90 shows an inverting clock input pin 14, so I think it counts each time it goes low.

Yes, i think so too that it should count when it goes low. But it doesn't in the simulating program 

Connect that to your input pulse you want to count. It won't count on its own. The count pulse must be a logic level input

i connect pin 14 to pulse generator (1Hz, 10Vp-p), but it doesn't count... i think there is something wrong in the circuit i connect in Multisim.

Hello,
I tried to simulate this circuit http://www.electronics-lab.com/projects/misc/012/index.html in Multisim, should pin 14 (count in) be connected to a 5V or GND or ...?

Can you help me please 

Hi Audioguru,
Yeah, i saw it. It's so cool, amazing products... they are the leader in automotive audio systems.  ( speakers, amps, navigators ... in best cars Lexus , Porsche & Chrysler  ...  )

aha, thanks for the info 

Hi,
Is "Harman Kardon" a swedish enterprise/company?

I'm just curious to know... 

Thanks

Hi Mr. Audioguru,
Thanks for the explanation of the "fake" power of the car stereo 
Yes im sorry i forgot to say how the speakers were wired. I chose 8ohm each to get 4ohm in parallel connection.

Thanks in advance

Hi,
Fig. A is a normal connenction of car stereo which has 4-channels. Can i connect like fig. B? What are the consequences, if there are? Can the stereo be overlaoded?

Thanks in advance.

Hi,
I've a digital sattelite reciever (samsung) which doesn't detect any signal... I'm sure that the dish is in right position (my other reciever is detecting signal and working normally at the same position of the dish). Do you think it's a physical wrong for eg (module or something like that) or ... ?

Thanks