#1
alright this is the situation,

i bought my jcm 800 second hand(off of a buddy) had no probs with it till one of the tubes had a blue ring near the bottom. so i brought it in to get re-tubed(with matchable grove tubes) and biased. brought it home turned it on and let it sit around 20 mins before i turned it on all the way, 15-20 mins into warmin up my drummer noticed smoke coming from the head, and it smelt like something was burnning and two tubes were BRIGHT orange. my local music shop said it's prolly just bad tubes(the two bright ones). does this sound right? has anyone had a similer story?

side question:

i use a marshall jackhammer for a distortion pedal, its nice, but i don't get enough distortion from it. i can't do the pinched harmonics the way i used to? is it the pedal or me? and what would you guys recomend for a dist/od pedal?
fender aerodyne jazz bass>mxr el grande bass fuzz>boss odb-3>dunlop crybaby bass wah>randall rba 500 es/ampeg 8x10
#2
please don't use a distortion pedal or the overdrive on that jackhammer - sounds like crap!
#3
any help with the other conundrum?
fender aerodyne jazz bass>mxr el grande bass fuzz>boss odb-3>dunlop crybaby bass wah>randall rba 500 es/ampeg 8x10
#4
It sounds like bad tubes. Just turn up the channel volume on your amp and lower the master volume and youll get some great gain. the JCM's have plenty of gain
#5
wtf is wrong with you?

The standby switch PURPOSELY heats up the tubes. Why did you leave it on for 20 minutes?
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#6
Quote by drugfreeboy

i use a marshall jackhammer for a distortion pedal, its nice, but i don't get enough distortion from it. i can't do the pinched harmonics the way i used to? is it the pedal or me? and what would you guys recomend for a dist/od pedal?



why on earth are you using a distortion pedal with a jcm

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09 Seymour Duncan Pickup Booster
09 Fulltone OCD V.4
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Yeh the SICK! bit sounds a bit stupid.

#7
Channel Volume turned up with the master volume down will get you tones you want.

You shouldn't have retubed with Groove Tubes because they are overpriced rebranded tubes.

I suspect that your tubes are fine because some glowing and heat isn't bad at all. I think something like a capacitor is bad.
#8
Quote by sesstreets
wtf is wrong with you?

The standby switch PURPOSELY heats up the tubes. Why did you leave it on for 20 minutes?


power first on the jcm 800, then standby.


Quote by acdcrocks0323
I suspect that your tubes are fine because some glowing and heat isn't bad at all. I think something like a capacitor is bad.


what about the smoke and burning smell? it wasn't a normal glow. the whole tube was orange, while the other two were normal.
fender aerodyne jazz bass>mxr el grande bass fuzz>boss odb-3>dunlop crybaby bass wah>randall rba 500 es/ampeg 8x10
#10
Quote by sesstreets
wtf is wrong with you?

The standby switch PURPOSELY heats up the tubes. Why did you leave it on for 20 minutes?


There is nothing wrong with what he did. Putting your amp on standby turns on the heater filaments without any high voltage B+ hitting the tubes. The heating process of the amp is NOTHING compared the voltage that will hit the plates when you turn the standby to "off" (not that it matters as the heaters remain on whether the amp is in standby or not).

To the TS:

The blue ring in the old tubes is actually completely normal. What it sounds like is that the person who replaced your tubes did not rebias properly and the tubes were running way too hot. If they were glowing bright orange, then they're toast, its called redplating, where plates (the big gray component) is dissipating more power than it can safely handle (most people bias the tubes to 60-70% of maximum dissipation). Either that or the tubes are bad. Sometimes bad tubes have the tendency to drift after they've been biased, I've heard horror stories with some groove tubes and their tendency to drift.
Last edited by al112987 at Dec 14, 2008,