#1
Is there anyway to tell if your tubes are going bad? I have a Kustom Defender 112, it's my first tube amp and it is pretty great for what I paid. I have had it hooked up to a power attenuator for a while now so I can get the tubes burning hot at low volume. It sounded awesome, but over the last few weeks I have noticed a slight electronic burn smell when it's on for a while and lately I have noticed the highs are just slightly darker than before. Last night I turned it on, let it warm up on standby of course, and when I came back ten minutes later there was no power even though the power was on. I flipped the switch a few times, waited a couple minutes and tried it again, but nothing. I turn the gain and volume up all the way so I know I am really stressing the tubes which are cheap chinese generic factory tubes. Is this why my amp is not working? Did I just finally annihilate the crappy tubes or is this a more serious problem? All help is monumentally appreciated. BTW, I went ahead and ordered all new tubes for it, power and pre. Svetlana.
Guitarfaced
#2
Try that first, then come back to us.

You probably didn't need to replace the preamp section, tbh... But who knows. Did you try unhooking it from the attenuator?

It sounds like it was the tubes, though, despite the "electronic burn smell".... But I don't really remember what clean tubes smell like. My amp always smells like smoke, and when its running, hot smoke.
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#3
I actually just checked some stuff out and although the power indicator light does not come on the tubes still light up. I found 2 fuses that are burned up. What I mean is they are not blown completely, but are burned to the point that a multimeter shows no continuity so I am guessing that is whats going on. The 2 fuses are on the circuitboard directly beside 2 green wires coming out of the power transformer. Anyone think they just became too worn to operate anymore or is there something wrong with my power transformer??
Guitarfaced
#4
Replace the fuses. If they pop again, take it to a tech.
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#5
burning smell, blown fuses, and blown power tubes is bad bad

i would take it to a tech

i would not use the attenuator anymore. i wouldn't even turn it on and I'm the type who would normally want to figure this out on my own. I'm also not an amp tech.

how many watts is your Defender and what attenuator were you using?
#6
Quote by 311ZOSOVHJH
burning smell, blown fuses, and blown power tubes is bad bad

i would take it to a tech

i would not use the attenuator anymore. i wouldn't even turn it on and I'm the type who would normally want to figure this out on my own. I'm also not an amp tech.

how many watts is your Defender and what attenuator were you using?

Or just listen to 311.
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How do you say "I'm okay" to an answering machine?

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#8
Quote by RootsRockRebel
I turn the gain and volume up all the way so I know I am really stressing the tubes which are cheap chinese generic factory tubes. Is this why my amp is not working? Did I just finally annihilate the crappy tubes or is this a more serious problem? All help is monumentally appreciated. BTW, I went ahead and ordered all new tubes for it, power and pre. Svetlana.


There's your problem. First thing I do with new tube amps is throw the chinese tubes in the trash and put something in that will last longer than 5 minutes. Running an amp maxed out through an attenuator will put a great deal of stress on the power tubes, chinese tubes are not going to cope with that kind of use for long. On a side note, you don't want to be 'annihilating' tubes in your amp or you can damage all sorts of other stuff if the power tubes blow/arc etc etc. At the first sign/sound of trouble, test, diagnose and replace the faulty tubes.
Gear:
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Marshall DSL15H, Weber Speakers, Fender Champs (x2),
'63 Fender Reverb, Mosrite Fuzzrite, Joe Bonamassa Fuzz Face, Whiteface RAT
Vintage Tubes!
#9
Sounds like your power tubes are dying. You should have spares. How you test is by sticking in your spares and seeing if the fault goes away.
So, why don't you have spares young Johnny? Hmmm? Did we spend all our money on potions and powders? Tsssk tsssk.


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Last edited by Cathbard at Feb 2, 2012,
#10
I got plenty of spares, 50+ NOS tubes last time I checked
Gear:
Fender AVRI '62 Jazzmaster, Fender Gold Sparkle Strat (custom), Custom Swirled Roswell Rhoads
Marshall DSL15H, Weber Speakers, Fender Champs (x2),
'63 Fender Reverb, Mosrite Fuzzrite, Joe Bonamassa Fuzz Face, Whiteface RAT
Vintage Tubes!
#12
well, for what it is worth - the attenuator should be more like 150% of max power of the amp. So if the max power of the Defender is 50 watts, your attenuator should be 75w +.

I'm not an attenuator expert. What kind of attenuator is it?

Is this a 112 combo?

You can get some new power tubes obviously and see what happens.

I personally would inspect the circuit board but that can dangerous as you have to take the chassis out. I'm willing to help you as far as you want to go.