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TUBE AMP HELP!!!
I am new to tube amps, I just bought a small 20w all tube head and a Marshall 1x10 microcab, the amp was new but the cab was second hand and I cant get it to work. I plugged the head into the cab and plugged the power chord in, the head turns on and the lights come on and it changes channels and everything but no sound will come out of the cab. When I turn the head on, the speaker does make a noise like it turning on but it will not work, I read that its an 8ohm cab so I tried the 8 ohm output on the head but that didn't work so I tried the 16 and 4 ohm outputs and they didnt work either. also I'm new with tubes so this is probably a stupid question but the EL84's illuminate (which im pretty sure they're supposed to) but they also get hot and make the top of the head hot (its a metal casing), is that normal?
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Re: TUBE AMP HELP!!!
Yes, tubes getting warm and lighting up is normal.
This may be a silly question, but you didn't mention it specifically: are you taking the amp off Standby after you've powered it up? (And also, because I know I've done it, the volume on the guitar is up too [emoji1]?)
If so, then the next test is to take the output of a music source (iPod, stereo, etc) to a quarter-inch jack and put it direct into the speaker cab - if it's working, you'll hear the music (don't worry about HOW it sounds, just whether you can hear it or not).
If you can't hear it, then you'll need to check the wiring to the speaker and/or the condition of the speaker itself.
If the speaker cab is working fine, then your issue is with the amp - given your lack of experience, I would get it to an amp tech locally (if there is one). That or, if you bought it from a local store recently, take it back and get them to either prove it works, or give you a replacement. In both cases, even though you've checked the speaker, make sure you take the cab as well, so they're testing apples to apples.
Tube amps have their quirks for sure, but don't buy into the 'mythical beast' stuff you read on the Internet - they're electronic devices, so it's simply a case of working out where the signal is getting broken/diverted to ground.
Best of luck ~Vince
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Re: TUBE AMP HELP!!!
Have a multi-meter? If so, plug the speaker cord into the cab and check the DC resistance (measure from tip to barrel on the other end of the cord). If it reads 5-6 ohms, the cab is OK. If it reads infinity, the cab wiring or speaker is open. If it reads 0, the cab wiring or speaker is shorted.
HTHComment
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Re: TUBE AMP HELP!!!
Sounds like the standby switch–most tube amps have them. If yours has one try flipping it the switch and see if that works.Comment
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Re: TUBE AMP HELP!!!
I know the standby switch and that was on "on" as well. I tried plugging my stereo and my phone into the cab and no sound came out, I then tried my multi-meter and it came up with 0 so its the cab, I have contacted the guy I bought it off and am taking it back to him soon as he thought it was working. With a new tube amp do you need to leave it on for a bit to break the tubes in or anything?Comment
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Re: TUBE AMP HELP!!!
It's good to leave the amp on standby for a little while to warm up the tubes.Originally posted by djent View PostThe opinions expressed above do not necessarily represent those of the poster and are to be considered suspect at best.
Lead guitarist and vocalist of...
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Re: TUBE AMP HELP!!!
+1 to thisOriginally posted by Beer$ View Post
Plus I will add that it is good to leave the amp on standby for a little while before turning off the amp.Comment
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Re: TUBE AMP HELP!!!
Update: I got a new Vox 1x12 cab and it still doesn't work, I've tried different cables, guitars, speakers and cabs and none of them work so I believe it is the amp that is broken. You can very faintly hear it, with the volume all the way up you can very faintly like barely hear it at all. What could be causing this?Comment
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Re: TUBE AMP HELP!!!
Maybe a cold solder joint the with the speaker output? Not sure; if you can hear something it means that it's some sort of resistance issue somewhere.Comment
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Re: TUBE AMP HELP!!!
I find it strange that both cabs were faulty. Connect a couple of leads to a nine volt battery and touch them to the speaker cable coming out of the cab. You should see the speakers move and might also hear some clicking. If the speakers move the cab is fine.
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Re: TUBE AMP HELP!!!
Standby for a minute or two on power up definitely safes wear and tear on the tubes, and makes them happier all around, don't understand the purpose when shutting down though. The heaters are on when it's in standby, that's the purpose of standby, so it's not like it's helping cool the tubes down or anything.Originally posted by treyhaislip View PostComment
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Re: TUBE AMP HELP!!!
If you ever turned on the amp without any speaker load (and the amp was live - off standby), then there was probably arching going on in the output transformer, which likely caused a short in the coil windings, which would explain a very very very low volume output from the amp (a big symptom of a wrecked OT). If the amp is an inexpensive (under ~$600) and mass-produced amp, a wrecked output transformer would mean your amp is "totaled". I find it somewhat unlikely that two cabs in a row were faulty. Unless you bought them "used" off of Cletus Jr. from Craigslist for a "good deal", then I'd start thinking it is the amp. Did you buy the amp new or used? Was it a floor model? Floor model tube amp heads always get switched on without a speaker connected by Guitar Center-kids who don't know what they're doing.
Also, when testing speakers with a multimeter, make sure the ohm measurement range is set to the lowest range (usually 200 ohms). If you have the range set to 20K, then the ~6 ohms DC for an 8 ohm AC rated speaker is seen as a negligible amount and is displayed as "0".
As for the standby switch, always let the amp heat up just a bit on standby before switching it into playing position, with the exception being newer Vox AC30s with a tube rectifier (use the standby switch on models with the SS rectifier). This is because not only do the tubes fully warm up before the rectifier tube even heats up - allowing current to pass through to the rest of the amp, but also when switching from "standby" to "on", the tube rectifier sees an overloading voltage spike, which rapidly wears the tube, and quickly causes it to blow. So in the case of that amp, keep the standby always on "on" and just use the power on/off switch. Also, it isn't too critical that you switch the amp to standby before turning the amp off. Turning the amp off without going to standby first doesn't put and stress or wear anywhere on the amp, but actually does drain the filter capacitors (whose held charges power the amp for a few seconds after you flick the power switch). Turning the amp to standby first just removes the output transformer from the circuit so the tubes are kept warm - you're really just using power to do nothing.Comment
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Re: TUBE AMP HELP!!!
It's a brand new amp, I contacted the retailer and they suggested that maybe the Bypass loop was off, it was. all this trouble just because the bypass loop was off -_- stupid me. It works fine now and sounds amazing through this Vox 1x12Comment
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