Re: Oscilloscope arrived - black market sucks

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: David Speck <dave-at-davidspeckmd-dot-org> 

Kreso,
It sounds like your scope is actually working OK, especially if you have a 
recognizable trace on the screen.

Your nine volt output transformer is the output rating under its designed 
load.  The scope presents nearly no load, so the voltage will probably be 
higher. Further, the specs on small transformers are usually pretty loose, 
and if your line voltage is high, you'll also read high.
Also, you have to remember that the scope is showing peak to peak values, 
which will be 1.414 * 9 volts, or 12.7 volts.  With all these factors 
considered, the displayed trace sounds about right.

Scope have a very high impedance input, and will pick up all sorts of 
interference from the air.  It's perfectly normal to see a trace on the 
screen if you have an open wire connected to the input.  If you touch the 
wire, the trace will increase as your body will add to the antenna effect.

I'm not sure how you connected the diodes. but it you wire a correct diode 
bridge, with a 10K ohm resistor for a load, you should see a proper 
pulsating DC waveform.

Keep at it.  Scopes actually display what is out there, which is not always 
the same as you would think from working with paper circuits.
Try to find someone experienced with electronics who can help you learn to 
use the unit.

Dave
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I tried conecting 9 VAC transformer at input, scope measures 15 V with odd 
showing, ok i tried adding one diode no improwment 2 dioes nothing, greatz 
then i get only a line it cannot be a line only with a greatz - right? It 
cannot be full DC with only 4 diodes? Or when i touch the table the waveform

>gose here and there it moves by it self, scope is not fizically connected to
>table it does  alot of crap etc and etc.