29 Jan
2014
29 Jan
'14
7:09 p.m.
I don't understand where this mythology about
capacitors has come from. They
Nor do I, really...
The only thing I can think of is in valve (tube) amplifiers there's often
a coupling capacitor from the anode (plate) of the driver to the grid of
the output valve. If this goes leaky, it appliles a +ve bias to said
grid, the ouput valve conducts heavily, often damaging the valve and the
output trasnformer.
This is one capacitor that does fail quite often (a slight leak is often
enough to upset things) and which has someaht serious consequences (I
have sene the anode of an EL34 glow bright orange due to this).
So I guess there are times when it's important to be sure the capacitor
is good. But in 99% of computer evices, if a cpacitor fials it does no
otehr damage. And they don't fail that often.
get blamed for every possible kind of equipment
failure whether or not there
is evidence to suggest a capacitor might be responsible. It is routinely
suggested that any and every problem can be solved by something which has
come to be known as "re-capping" which I suspect means replacing all the
capacitors in a device. It has even been suggested that no vintage
restoration is complete without replacing all the capacitors.
YEs, I've heard that rubbish too...
I have had capacitors fail. In fact the last repair to a classic computer
device that I did was a dead shorted electrolytic capacitor. But I just
replaced that oen capacitor, not all the ones in the unit
And I reckon I've had more LSI ICs fial than capcitors, for all I have
used many more capaciutors.
As ever, I collect the symptoms, then think avout them before replacing
anything. If it's a capacitor that's failed, then of course I replace it.
But I don't just replacve capacitors in the hope it will cure the proble,m.
-tony