the normal glow fades away, making a feedback like sound (coming from speakers), dies and then immediately lights up again, but continously to a bright orange bright glow.
one tube is microphonic.
my amp's got 4 EL84's and this problem only happens to 2 tubes (which are beside each other).
before this, i started to blow fuses.
do you think this is simply tubes going bad?
oh btw, this is a guitar amp. class-a 30w, 3xecc83 preamp, 4xel84 power, combo with 1x12 speaker. i suspect i rattled the tubes to death by playing at really high volumes on-stage? or could it be another problem other than the tubes?
thanks in advance
one tube is microphonic.
my amp's got 4 EL84's and this problem only happens to 2 tubes (which are beside each other).
before this, i started to blow fuses.
do you think this is simply tubes going bad?
oh btw, this is a guitar amp. class-a 30w, 3xecc83 preamp, 4xel84 power, combo with 1x12 speaker. i suspect i rattled the tubes to death by playing at really high volumes on-stage? or could it be another problem other than the tubes?
thanks in advance
What amp, Classic 30? SOmething else?
EL84s are not sturdy tubes and they don't last a long time. When they shake themselves loose inside - and they eventually do - things short to other things. In an EL84 amp, when fuses blow, 98% of the time it is a bad power tube. If a power tube was microphonic that is a bad sign for that tube.
In an amp with four EL84, there are two tubes for each phase of the push/pull. They are wired together. if one shorts out the bias supply, then both tubes of that side lose bias. SO one bad tube can affect the others.
Try a new set of EL84.
EL84s are not sturdy tubes and they don't last a long time. When they shake themselves loose inside - and they eventually do - things short to other things. In an EL84 amp, when fuses blow, 98% of the time it is a bad power tube. If a power tube was microphonic that is a bad sign for that tube.
In an amp with four EL84, there are two tubes for each phase of the push/pull. They are wired together. if one shorts out the bias supply, then both tubes of that side lose bias. SO one bad tube can affect the others.
Try a new set of EL84.
its a Laney VC30, a Vox AC30 clone.
with your explanations, i now see why the other power tube, though still not microphonic and seems to be ok, also glowed like the microphonic/bad tube and became bad too.
im afraid to try a new set of tubes, as the amp might wreck them the minute i power it up ($). is this going to be the scenario (blowing new tubes) if Miles Prower's post is true?
i play it on a stage with lethal volumes (earplug zone). very small stage made up of wood, with a 450w amp driven 4x10 bass cab, and several guitar amps and monitors running full blast. is there any way i can minimize the tubes from getting rattled by the sound (from other sources and from its own speaker)?
currently the tubes installed are 4 Sovtek EL84's for the power section, 2 ECC83's branded as Ruby, and another ecc83 without any brand (i assume its a china tube?)
with your explanations, i now see why the other power tube, though still not microphonic and seems to be ok, also glowed like the microphonic/bad tube and became bad too.
im afraid to try a new set of tubes, as the amp might wreck them the minute i power it up ($). is this going to be the scenario (blowing new tubes) if Miles Prower's post is true?
i play it on a stage with lethal volumes (earplug zone). very small stage made up of wood, with a 450w amp driven 4x10 bass cab, and several guitar amps and monitors running full blast. is there any way i can minimize the tubes from getting rattled by the sound (from other sources and from its own speaker)?
currently the tubes installed are 4 Sovtek EL84's for the power section, 2 ECC83's branded as Ruby, and another ecc83 without any brand (i assume its a china tube?)
I would also tend to believe that the most likely problem is a bad tube, which likely led to at least one more bad tube. Another possibility is loss of bias due to a bad cap.
I find that a thick blanket like the kind professional furniture movers use under the amp helps isolate the amp from a vibrating stage.
I find that a thick blanket like the kind professional furniture movers use under the amp helps isolate the amp from a vibrating stage.
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