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help with homebrew receiver!

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July 10th 03, 09:40 PM

Active8

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In article , says...
If you're using a diode bridge like most people do these days, and the
diode bridge output terminals (+ and -) are reversed, the filter
capacitor would get hot and the receiver wouldn't work.

As others have pointed out, an electrolytic capacitor with reverse
voltage applied can catch fire or explode. Be careful when
troubleshooting while the capacitor is unhappy. When you do find the
problem, it would be a good idea to replace the capacitor.

i've had a couple explode, usually from overvoltage from a shorted
series pass reg, i think. nice thing about (some? most?) electrolytics
is that X that's scored into the top so it blows straight up. i'm glad
my face wasn't over top of it, though. even with safety glasses, it's
not something i'd like to experience.

mike c

Roy Lewallen, W7EL

Active8 wrote:
In article , lid
says...

Active8 wrote:

In article ,
says...

Tom:

The hot cap has two likely possibilities: either the cap is shorted
internally (an ohmeter check will show leakage) or you have bad diode(s) so
AC is being applied to the cap. An ohmeter will show the diodes as bad.

a backward diode will supply AC to the cap, also

No, it won't.

oops. right. 1 diode backwards in a full wave (not a bridge) rectifier
would short the xfrmr.

It will however supply the wrong polarity of DC, which could indeed
cause these symptoms.

I would think some other semiconductors might be running rather hot too
if that were the case.

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