[Diy_efi] Re: FW: WB testing problems - again

[Phil Hunter]

> I'll try this again since I have not seen it yet...
> 
> Okay, I have done more testing.
> 
> Bottom line is that C12 IS leaking.  When I disconnect it (at the
> + terminal) everything goes to 7.75-7.8 volts, particularly
> terminal 5 of U3.
> 
> So, now, what is the solution to this?  I had already replaced
> the cap itself with no change.  Any ideas?  What will this affect?
> 
> I am not going to continue the rest of the tests until I
> understand the impact of this problem a bit better.
> 
> Any ideas?
> 
> Thanks,
> Steve

C12 is an electrolytic cap, most are polarized and will leak
badly if installed backwards, I'll bet it's that simple.

On my boards stuffed w/ the group buy kit, C12 is dark blue
w/ a light blue stripe indicating (-), all 4 'lytics in that
area on the PCB have the stripes toward the J8/Vout edge of
the board.

Considering the impedances, etc., if C12 was backwards, you
can probably "get away" w/ just reversing it, if the voltage
is now correct, I'd move on and not worry about replacing it.

Electrolytics also have a tendency to lose capacitance and
increase leakage w/ age, not normally a problem for years
tho', I mention it only if you're using caps salvaged from
junk or purchased surplus and you don't know how long ago
they were manufactured.

regards,
philh
(digest)

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