I have a QSC PLX3402 that has been in storage for a couple years. I recently powered on another amp that was also in storage and it promptly went "BANG!!" as soon as I turned it on. I'm in the process of troubleshooting that one. I have since learned about Dim Bulb Testers and I'm going to make one. My question is what wattage should I use for the bulb? The manual for the PLX3402 says it uses .9 amps at idle. .99A x 110V = 99 watts. If I use a 100 Watt bulb, wouldn't that allow all the current the amp needs and therefore not offer much protection? Or am I completely wrong on this? I have read that 100W is good for "most amps" but I'm not sure if this amp falls into that category. So what would be the best wattage to use here? Thanks
Your amplifier should play normally without fully lighting a bulb that is roughly 1.5 to 2 times the amp's stated wattage.
More information about bulb wattage choice here: https://www.antiqueradio.org/dimbulb.htm
More information about bulb wattage choice here: https://www.antiqueradio.org/dimbulb.htm
No. The lamp and the amp will be in series and share the voltage between them. Neither one will receive the full 110V.
Unfortunately, it is not easy to calculate how the 110V will be divided between the two since neither one is a linear device and they behave differently when they receive less than the full rated mains voltage. Two 100W incandescent bulbs will receive 55V each but the situation is different when you connect different types of appliances in series.
Maybe you should start with a lower wattage bulb. That will limit the current to a lower level and produce a smaller bang if the amp has a serious short circuit. If nothing blows up, you can step up the bub wattage.
Remember that you must use an incandescent bulb, not LED, fluorescent or some other type of device.
EDIT: Just saw Ant Moore's post. I didn't know what the PLX3402 is. He's right. A device with SMPS may not "play nice" with a series bulb. The principle holds with linear supplies.
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Thanks for the reply and the link. It's making making much more sense now
This is interesting. I haven't heard this. I'm fairly certain I've seen reputable youtube videos use a dim bulb with switching power supplies. I'll have to double check. I have heard that modern amps aren't good candidates for use with a variac. Not sure which is correct.
Thanks for the reply. It looks like I'll have to dig into this further.
I hope I'm not opening a huge can of worms here, I'm honestly just trying to find a safe way to power this thing on. Here is a video of a couple high power class D amps and he is using the dim bulb tester when powering them on. The link is time stamped: Dim bulb with Class D amps