Quit to Home Page
back to last page Page
Capacitors
Capacitors are probably the cause of most faults, even when you get a lineoutput transistor(LOPTR) gone , the probable cause was a capacitor.
There are two main type Electrolytic , and Non electrolytic
Electrolytic Capacitors are like small batteries, usually polarised (must be connected the right way round )
and are usually marked with the capacity, voltage and temperature, example :- 100uf50v 105degree
They rarely have voltages over 400v
They can be any color or shape, but are mostly black and round with a white strip down one side(denoting the negative pin side)
They often fail with no external signs showing, but if the black plastic sleeving is shrinking away from the top, or the sides are wrinkled, then they are getting HOT, either by internal heat generation or by something nearby getting hot.
another sign is that the top silver surface is swelling , caused by gas generated inside, often due to over voltage (check ht level)
You can detect errors with a capacitance meter, and a ESR meter (effective series resistance)
I do not have an ESR meter so I use a 400v 470nf cap in series with my multimeter (on the AC volts range)
reading lots of good working sets will give you a feel of what a good cap may read for your meter/cap
and then when you meet a bad one you will see the difference
I also have an oscillscope to look at the waveform (idealy a flat line)
Sometimes if the fault happens after the set is warm, and is not mechanical(dry joints) then I let the set get hot (10 mins) and carefully touch the tops of all the
electrolytic caps to see if any are hotter than usual.
back to last page