Can someone explain to me this?

[MaXiZ]

An externally hosted image should be here but it was not working when we last tested it.

 

[IVX]

Interestingly..

 

[li_gangyi]

I would say this is part of a SMPSU...probably the part AFTER the switching controller and MOSFETs...

 

[MaXiZ]

that cos' other can be?

 

[li_gangyi]

So what do you want the rest of us to explain???

 

[runebivrin]

Most DVM:s don't particularly like measuring 100kHz square wave, so it'll likely not give very accurate results.
Another, less scientific reason would be that you're using the DC range of your DVM to measure AC (been there, done that )

Rune

 

[megajocke]

The frequency is too high for your multimeter...

 

[MaXiZ]

So what do you want the rest of us to explain???

how is that possible!

The frequency is too high for your multimeter...

For my multimeter????

 

[JOE DIRT®]

the meter was set to DC when trying to read an AC voltage

 

[li_gangyi]

Probably...or there is a problem with ur multimeter??? Probably not...

 

[megajocke]

Whose are those voltage and current markings in red? That's what a normal multimeter probably would show at that kind of frequency.

 

[PMA]

Joe Dirt is right, DC voltmeters usually do not read AC voltages ...

 

[li_gangyi]

Yeah...try switching ur range to AC and then re-measure...tell us what you get...

 

[iso_510M]

Use an oscilloscope and you'll see a high frequency (40KHz ?) modified sine wave around 30Vp-p, with respect to ground. (42V x .707). Have repaired many, many 12V amplifiers

Jim

 

[li_gangyi]

Problem is...he does not have a Scope...

 

[Jay]

Li_gangyi, I think MaXiZ needs the answer, not the scope

 

[audiofan]

Voltage at the transformer is AC must be measured with an AC voltmeter that can work at the working frequency. Same applies to the current flowing from tranformer to the diode. You have DC voltage and current only at the output of the full wave bridge them you may measure with DC voltmeter

 

[li_gangyi]

Yeah...just change ti to AC and try and see the voltage...we would actually want you to have a scope to look at it better...but I guess he doesn't have one...