read this or die
You may have seen warnings on TV's and other electronic appliances that said that if you open the case and touch anything inside it you will be instantly electrocuted. Ever wonder if that was an exaggeration? I always did. How else do people repair the things?
WRONG!
Our natural inclination is to think that once we turn off an electronic device, all the electricity in it gets sucked into the wall socket and disappears safely. That is not correct.
As applied to guitar amplifiers in particular, you must be aware that every circuit contains semiconductors known as "capacitors." In the photo above, the two green horizontal cylinders toward the right and the larger vertical gold cylinder toward the left are capacitors. If you look closely, circling the bottom of the gold cylinder is a row of "+ + + + + +" symbols. Although harder to see, circling the top of the cylinder are a row of "- - - - - - - " symbols. That indicates that this is a particular type of capacitor known as an "electrolytic" capacitor. IT IS EXTREMELY DANGEROUS.
On Hilgen amplifiers, there is a bundle of four electrolytic capacitors stuffed in a metal can on the other side of the chassis. So you may not know they are there. They are called "filter" capacitors. THEY ARE ESPECIALLY DANGEROUS.
So as to keep this simple, think of an electrolytic capacitor as a type of battery. It can store a several-hundred volt charge for a long time -- you're best off assuming it can do so forever. It doesn't matter if the amp hasn't been used or even plugged in for a long time. The charges can still be there, waiting to kill you.
You will read a lot of opinions on how you can safely drain the electricity from an amp circuit. Some refer to turning off the power, unplugging the amp, and flipping the standby switch on. I don't know how reliable that method is, but most Hilgens do not have a standby switch anyway. So much for that. SO FAR I have found it safe and effective to take a jumper cable with WELL-INSULATED alligator clips, attach one clip to the chassis, and then attach the other clip to the lug for pin 1 of the first preamp tube. After waiting 30 seconds or so, the voltage should have drained to safe levels. But you can't possibly know that unless (a) you own a volt-ohm meter or other multimeter that will measure voltage and (b) YOU KNOW HOW TO USE IT ACCURATELY AND SAFELY.
You must at least test all the capacitors for stored voltage. Better to make spot checks all over the circuit, once the caps are discharged. A few volts MAY be ok - but make sure you have the meter set on the right range, or you could be measuring a couple of hundred or thousand volts, rather than single volts. You're better off waiting until you measure no voltage at all, at any range.
IF YOU DON'T UNDERSTAND THE ABOVE DISCUSSION THOROUGHLY, NEVER GO BEYOND TAKING THE BACK OFF THE CABINET AND TAKING A PHOTO OF THE INSIDE OF THE CHASSIS FROM A SAFE DISTANCE. NEVER, EVER, TOUCH ANYTHING INSIDE THE CHASSIS WITH ANY PART OF YOUR BODY OR WITH ANY NON-INSULATED OR CONDUCTIVE OBJECT, OR PUT YOURSELF IN A POSITION WHERE YOU MIGHT ACCIDENTALLY DO SO.
IF YOU DON'T BELIEVE THE ABOVE DISCUSSION, DON'T EVEN TAKE THE BACK OFF. YOU ARE GOING TO ELECTROCUTE YOURSELF. TO DEATH. I DON'T WANT THAT TO HAPPEN TO YOU.
WRONG!
Our natural inclination is to think that once we turn off an electronic device, all the electricity in it gets sucked into the wall socket and disappears safely. That is not correct.
As applied to guitar amplifiers in particular, you must be aware that every circuit contains semiconductors known as "capacitors." In the photo above, the two green horizontal cylinders toward the right and the larger vertical gold cylinder toward the left are capacitors. If you look closely, circling the bottom of the gold cylinder is a row of "+ + + + + +" symbols. Although harder to see, circling the top of the cylinder are a row of "- - - - - - - " symbols. That indicates that this is a particular type of capacitor known as an "electrolytic" capacitor. IT IS EXTREMELY DANGEROUS.
On Hilgen amplifiers, there is a bundle of four electrolytic capacitors stuffed in a metal can on the other side of the chassis. So you may not know they are there. They are called "filter" capacitors. THEY ARE ESPECIALLY DANGEROUS.
So as to keep this simple, think of an electrolytic capacitor as a type of battery. It can store a several-hundred volt charge for a long time -- you're best off assuming it can do so forever. It doesn't matter if the amp hasn't been used or even plugged in for a long time. The charges can still be there, waiting to kill you.
You will read a lot of opinions on how you can safely drain the electricity from an amp circuit. Some refer to turning off the power, unplugging the amp, and flipping the standby switch on. I don't know how reliable that method is, but most Hilgens do not have a standby switch anyway. So much for that. SO FAR I have found it safe and effective to take a jumper cable with WELL-INSULATED alligator clips, attach one clip to the chassis, and then attach the other clip to the lug for pin 1 of the first preamp tube. After waiting 30 seconds or so, the voltage should have drained to safe levels. But you can't possibly know that unless (a) you own a volt-ohm meter or other multimeter that will measure voltage and (b) YOU KNOW HOW TO USE IT ACCURATELY AND SAFELY.
You must at least test all the capacitors for stored voltage. Better to make spot checks all over the circuit, once the caps are discharged. A few volts MAY be ok - but make sure you have the meter set on the right range, or you could be measuring a couple of hundred or thousand volts, rather than single volts. You're better off waiting until you measure no voltage at all, at any range.
IF YOU DON'T UNDERSTAND THE ABOVE DISCUSSION THOROUGHLY, NEVER GO BEYOND TAKING THE BACK OFF THE CABINET AND TAKING A PHOTO OF THE INSIDE OF THE CHASSIS FROM A SAFE DISTANCE. NEVER, EVER, TOUCH ANYTHING INSIDE THE CHASSIS WITH ANY PART OF YOUR BODY OR WITH ANY NON-INSULATED OR CONDUCTIVE OBJECT, OR PUT YOURSELF IN A POSITION WHERE YOU MIGHT ACCIDENTALLY DO SO.
IF YOU DON'T BELIEVE THE ABOVE DISCUSSION, DON'T EVEN TAKE THE BACK OFF. YOU ARE GOING TO ELECTROCUTE YOURSELF. TO DEATH. I DON'T WANT THAT TO HAPPEN TO YOU.