Troubleshooting Your Tube Amplifier

today we're going to show you how to troubleshoot your habit in the event that you think you've got a bad tube we'll go over how to determine which tube is bad and in which section the power or the preamp section before we begin we need to go over a few safety precautions when dealing with the tube amps you may need to expose some of the amp circuit in order to get to the tubes at any given time a point of contact in the circuit could be holding a high amount of voltage it is recommended that you unplug the amp and let it sit for at least 15 minutes to allow any charged components to discharge it is also recommended that you wear some sort of rubber glove for extra protection please be sure to have the amplifier turned off and unplugged when touching anything inside the amp while it is normal to hear noise coming from your tube amp due to analog circuitry in just the nature of amps you might hear crackling sound like popcorn or what may sound like feedback or micro phonics if this occurs you've likely got a bad tube if you're hearing microphonic s-- you can isolate the tube by gently tapping on it with the amp on if it rings when you tap on it that's a bad tube to isolate a crackle or pop you'll mostly have to find it by trial and error by swapping out tubes try turning the volume up and down if it changes the volume of the noise you're hearing then the problem lies in the preamp tubes if not it's a power tube if you happen to have multiple channels on the amp does the problem happen only on one channel if so it's going to be a preamp tube knowing which channel makes the noise can also help narrow down which preamp tube is causing the problem refer to your manual for more information on which tubes are for which channel these symptoms can also be caused by the reverb tube you can check the reverb by turning the reverb all the way off if the noise goes away the reverb tube is bad refer to your manual to see which tube governs the reverb once you've identified a problem tube you can replace it when removing preamp tubes be mindful of the direction they're facing when taken out they must go back in the exact same way they came out otherwise you may damage the tube or the tube socket power tubes have a guide on the bottom that must be correctly inserted into the tube socket make sure the guide is lined up with the groove in the tube socket preamp tubes can be replaced one at a time but be sure to replace it with the same type of tube power tubes must be replaced in matched sets if you have a bad power tube replace them all again make sure the power is off and the amp is unplugged when touching anything inside the amp if you're not getting any signal from your amplifier there are a few things you can do to isolate the problem if the amplifier does power on first check to see if your amp has an HT fuse on the back panel when the HT fuse blows the power will come on but the speaker will be completely silent without the typical background hum or hiss knows if this fuses bad replace it if it continues to blow you've likely got a bad power or rectifier tube if the HD fuse is fine and your amp has an effects loop try plugging your guitar into the return jack this will bypass the preamp section and take you straight to the power amp if you get signal and the signal will be weak then you know that the preamp is where the problem lies if you do not get signal your problem is likely a power tube if you've determined that the problem lies in the preamp section and you have extra tubes try swapping a good team from one of the tubes in your amp until you get signal just make sure it's the same model make sure that the power is turned off during any tube replacement if the amp does not power on you've likely blown the main power fuse you can usually find these on the back of your amp when a main power fuse blows it's very likely that you've got a bad power or rectifier tube to verify this remove all the power and rectifier tubes by gently wiggling and pulling them out and replacing the fuses next turn the amp on if it stays on then the main fuse is good but you have a bad tube if the main fuse still blows you've got a bigger problem and you need to send your amp in for service if it's a power of rectifier tube that's bad we need to isolate it to do this insert the rectifier tube if your amp has them one at a time with the power off be careful to align the groove in the tube socket with a guide on the bottom of the tube after inserting each tube turn the power on then right back off if you see a flash of light from the tube it's bad if not turn the power back on and leave it on if the amp remains on this tube is fine and you can continue with any remaining rectifier tubes once you verify that your rectifier tube or tubes are okay it's likely that your power tube is causing the problem while rectifier tubes can be replaced one at a time power tubes must be replaced in matched pairs because of this you should replace all the power tubes at once to avoid damaging both your tubes and your amplifier as long as you use the same model power tube with the same rating you shouldn't need to rebuy us the amp if you end up changing the type of tube you'll need to have the amp re biased by a trained amp technician if after replacing all the power tubes you're still blowing the fuse on your amp there is an internal problem with the amp and it will need to come in for service

Channel: Sweetwater

Views: 494,396

Keywords: tube amplifier, tube amp, tube amp repair, tube amp troubleshooting, tube amps, valve amplifier, how to change tubes on a guitar amp, vacuum tube amplifier, amplifier, how tube amps work, how to bias a tube amp, guitar amp repair, tube amp hum, tube amplifier sound, tube amp noise, amp, changing tubes in amp, marshall tube amp, tube amp maintenance, microphonic tube, sweetwater

Id: UnEO10x8VUo

Length: 6min 20sec (380 seconds)

Published: Wed Aug 21 2013