So, in the process of changing out the fans in one of my crown xls802’s, I lost focus for just one second and had a nice little firework show….
I was installing a voltage regulator on the fans because good god are they ever loud and I’ve never once had these things get above ~70° so, I can’t afford a bit less airflow. I’m also replacing the factory fans with some new noctua fans. Got the fans replaced and installed, no problem.
Well, I was setting the voltage with the regulator, got it right, and before realizing if, still had the amp plugged into the wall(no input or load), and set the regulator down on the heat sink for closest to the main cap bank. Had a big spark and pop, then everything died. No smoke or smell though, so I was feeling optimistic. More or less, the 12v power and ground shorted across that heat sink.
So I unplug everything, make it all safe, and try turning the amp back on. I now have no front lights and no power on the fan leads. The CB is still closed, front power button is fine, voltage is fine everywhere on the transformer, but still nothing on the fan circuit or front lights. So, do we think I maybe “lucked out” and it’s just something in the 24v circuit that I blew, or is it pretty much guaranteed that I’ve got a buggered transistor or two as well since that’s basically what it shorted across?
I was installing a voltage regulator on the fans because good god are they ever loud and I’ve never once had these things get above ~70° so, I can’t afford a bit less airflow. I’m also replacing the factory fans with some new noctua fans. Got the fans replaced and installed, no problem.
Well, I was setting the voltage with the regulator, got it right, and before realizing if, still had the amp plugged into the wall(no input or load), and set the regulator down on the heat sink for closest to the main cap bank. Had a big spark and pop, then everything died. No smoke or smell though, so I was feeling optimistic. More or less, the 12v power and ground shorted across that heat sink.
So I unplug everything, make it all safe, and try turning the amp back on. I now have no front lights and no power on the fan leads. The CB is still closed, front power button is fine, voltage is fine everywhere on the transformer, but still nothing on the fan circuit or front lights. So, do we think I maybe “lucked out” and it’s just something in the 24v circuit that I blew, or is it pretty much guaranteed that I’ve got a buggered transistor or two as well since that’s basically what it shorted across?
I tried to download the xls802 schematic and eserviceinfo locked up my op system. So it is up to you to do it and post it here. XLS1000 schematic I do have is a switcher supply amp, which is not for newbies to repair.
If you are prone to the kind of mistake of changing parts with the amp plugged in, in no circumstance attempt to repair a switcher supply amp. Those are hugely dangerous, even unplugged. Great energy has to be discharged from mains peaking caps before you touch any metal inside. Such discharge is done with a resistor with alligator clip leads using only one hand. Transformer supply amps are slightly safer to repair, although 60 v rails can kill you too if you use two hands to measure any voltage over 25. Current across your heart can stop it.
After a verification is made that the small blade of a 120 vac NEMA outlet in your house is actually the hot, then in the Edison part of the world (western hemisphere) a outlet strip can be used to turn off the AC. Appears you are located in US. I've lived in 2 houses where the black wires were wired neutral, so don't assume this fact. Test it. Black is ground in cars & consumer electronics; black is death in the house wiring. The big blade is supposed to be at the same voltage as the round ground pin. Many ground pins are fake wired instead of run back to the box, so don't assume the round pin is ground either. Compare it in voltage to a gas pipe.
An amp is not bricked IMHO until the a transformer is damaged or some part not made anymore is blown. Crowns have some of the latter, but not in the damage prone areas. Unique parts are in the too much high freq detection area, which doesn't usually blow.
Additional safety points, wear no jewelry on hands wrists or neck. ! v at high amperage can burn your flesh to charcoal through a ring. Wear safety glasses, especially unsoldering. Solder can splash and parts can explode. Do any testing of a transformer amp with a 60 w incandescent bulb series the AC input. This reduces the size of explosions. Can't be done on switcher supply amps. I have my incandescent bulb base inside a grounded metal case with a circuit breaker on input, in case the wires pop off the base screws. Screws of sockets are made for solid wire, and electronics uses stranded.
If you are prone to the kind of mistake of changing parts with the amp plugged in, in no circumstance attempt to repair a switcher supply amp. Those are hugely dangerous, even unplugged. Great energy has to be discharged from mains peaking caps before you touch any metal inside. Such discharge is done with a resistor with alligator clip leads using only one hand. Transformer supply amps are slightly safer to repair, although 60 v rails can kill you too if you use two hands to measure any voltage over 25. Current across your heart can stop it.
After a verification is made that the small blade of a 120 vac NEMA outlet in your house is actually the hot, then in the Edison part of the world (western hemisphere) a outlet strip can be used to turn off the AC. Appears you are located in US. I've lived in 2 houses where the black wires were wired neutral, so don't assume this fact. Test it. Black is ground in cars & consumer electronics; black is death in the house wiring. The big blade is supposed to be at the same voltage as the round ground pin. Many ground pins are fake wired instead of run back to the box, so don't assume the round pin is ground either. Compare it in voltage to a gas pipe.
An amp is not bricked IMHO until the a transformer is damaged or some part not made anymore is blown. Crowns have some of the latter, but not in the damage prone areas. Unique parts are in the too much high freq detection area, which doesn't usually blow.
Additional safety points, wear no jewelry on hands wrists or neck. ! v at high amperage can burn your flesh to charcoal through a ring. Wear safety glasses, especially unsoldering. Solder can splash and parts can explode. Do any testing of a transformer amp with a 60 w incandescent bulb series the AC input. This reduces the size of explosions. Can't be done on switcher supply amps. I have my incandescent bulb base inside a grounded metal case with a circuit breaker on input, in case the wires pop off the base screws. Screws of sockets are made for solid wire, and electronics uses stranded.
Honestly, it was more of a “awesome, this regulator idea is actually going to work” excitement, mixed with just losing focus for a second. I’ve had quite a few electronics opened doing smaller repairs before and never once made a mistake THIS bad. That’s another reason that I’m so frustrated with myself, honestly.
As for my houses wiring….I’ve been an electrician for about 15 years now and wired my house myself so, I’ve got that part covered. Haha. Not sure what you were saying in your explanation there about voltage but, it’s “supposed” to be “big blade” = neutral, “small blade” = 120v, and then obviously the ground. You are right about some people using a jumper from the neutral to ground to try to “make” a ground and….just no. Don’t do that. It was a trick back in the day when grounded receptacles first came out, but it can be more dangerous than helpful in most cases. 😂.
From what I can tell, the torroidal transformer in here seems to be fine. I’ve got a feeling that it may be the bridge rectifier and possibly the transistors that are attached to the heat sink that it shorted in(T03 style). So, when I get a chance, I’ll pull the boards out and just do some resistance and diode tests to see if I can find anything. I’m for sure going to do my best to do strictly static testing with no power applied. I’m hoping that none of these massive filter caps are dead….
As for my houses wiring….I’ve been an electrician for about 15 years now and wired my house myself so, I’ve got that part covered. Haha. Not sure what you were saying in your explanation there about voltage but, it’s “supposed” to be “big blade” = neutral, “small blade” = 120v, and then obviously the ground. You are right about some people using a jumper from the neutral to ground to try to “make” a ground and….just no. Don’t do that. It was a trick back in the day when grounded receptacles first came out, but it can be more dangerous than helpful in most cases. 😂.
From what I can tell, the torroidal transformer in here seems to be fine. I’ve got a feeling that it may be the bridge rectifier and possibly the transistors that are attached to the heat sink that it shorted in(T03 style). So, when I get a chance, I’ll pull the boards out and just do some resistance and diode tests to see if I can find anything. I’m for sure going to do my best to do strictly static testing with no power applied. I’m hoping that none of these massive filter caps are dead….