Aether II Diagnosis

[rdebolt]

So hypothetically: If someone (not me of course) were to say... try to check voltage at the 7805 regulator (That at the time had 5vts to it) and to accidentally slip with the volt meter and short out the voltage to that said regulator and now have no voltage to it. Where would he look? Hypothetically speeking! 

[n1ist]

Looking at the board in the wiki (I don't have one myself), I'd start by checking the fuse (the green blob next to the 12V AC INPUT label).  It's the most likely candidate.  The only other part between the AC input and the input to the regulator is the bridge rectifier, and those are quite hardy critters.

/mike

[sjb]

But before checking that, I would Hypotheically remove power from board and the shaking hands

[rm357]

If they, hypothetically speaking, still have more than 12v across the really big capacitor, its the 7805 that's dead. If they shorted the power coming from the capacitor... Well I bet that was a wake up call...

I got across a power lead on a 20 amp circuit with a meter lead once. Where the meter lead touched the chassis, it melted... And shot one giant spark...

[rdebolt]

But before checking that, I would Hypotheically remove power from board and the shaking hands

 

If they, hypothetically speaking, still have more than 12v across the really big capacitor, its the 7805 that's dead. If they shorted the power coming from the capacitor... Well I bet that was a wake up call...

I got across a power lead on a 20 amp circuit with a meter lead once. Where the meter lead touched the chassis, it melted... And shot one giant spark...

Ya If this were to really happen I think there would be a really quick flash ( I don't know if it would be the LED or something else) But I'll bet there would be a little cussing going on after that. 

[rdebolt]

Ok Now since all of the above has been hypothetical. When I do check for power  why would I only have 1.66 volts at the Ld33 Regulator? ( Before some idiot might short out the 7805 regulator)! 

[rm357]

I haven't looked at the circuit, but in most of RJ's designs, the 3.3v regulator is powered by the 5v regulator. That cuts down on the amount of excess voltage applied to the 3.3v regulator and thereby reduces the amount of heat it generates.

[rm357]

I haven't measured it, but I would expect something between 15 and 17 volts on the big capacitor. That feeds the 5v reg which should in turn feed the 3.3v reg.

12v AC usually means 12v rms - root mean square. The actual peak voltage is typically 1.4 times that number. If there is no load, that usually results in about 16 VDC with a lot of ripple... The big capacitor smooths out the ripple.