#1
Alright, so my clean channel is dead, and my gain channel is quiet.....I put a 12ax7 where a 12at7 used to be two days before this happened.....I was informed that they were interchangeable and it would give me a little more bite with my gain.....

Is that what broke my amp, or is this just spurrious and I have a power tube out or something? The EL34's look like they are lighting up, but....ideas...

thanks,
andy
"After all the practical reason why a majority are permitted to rule is not because they are most likely to be in the right, nor because this seems fairest to the minority, but because they are physically the strongest." -Henry David Thoreau
#2
what amp is it?
Whats the longest word?


Quote by timzee117
smiles

because theres a mile between the two s's!


/killme
#3
it's the Randall RG50TC combo. Sucks, because I was about to sell this amp and buy a 6505+ and a Marshall 1960cab!
"After all the practical reason why a majority are permitted to rule is not because they are most likely to be in the right, nor because this seems fairest to the minority, but because they are physically the strongest." -Henry David Thoreau
#4
The 12AX7 is similar to the 12AT7, but there is quite a difference in gain between the two.

IF you still have the 12AT7, put it back in. BUT make sure you do NOT do that with power turned on - NOT EVEN STANDBY!

Also, check that all the pins on the base of either tube are not bent or broken.
#5
No I don't mess with my tubes with it plugged in or anything. I did put it back. I've done as much trouble shooting as I can think of. I removed my FX loop, and switched cables, switched cables on my FX loop, etc. No pins broken or busted on my 12ax7's or 12at7.
"After all the practical reason why a majority are permitted to rule is not because they are most likely to be in the right, nor because this seems fairest to the minority, but because they are physically the strongest." -Henry David Thoreau
#6
Quote by dkcol
The 12AX7 is similar to the 12AT7, but there is quite a difference in gain between the two.

IF you still have the 12AT7, put it back in. BUT make sure you do NOT do that with power turned on - NOT EVEN STANDBY!

Also, check that all the pins on the base of either tube are not bent or broken.

I always switch my preamp tubes with the power turned on and left on standby.
#7
bump.....

anybody have any suggestions? should I try replacing power tubes? Is that a logical next step or what?....I gotta take it to my guy at the pro shop I think....
"After all the practical reason why a majority are permitted to rule is not because they are most likely to be in the right, nor because this seems fairest to the minority, but because they are physically the strongest." -Henry David Thoreau
#8
Instead of wasting money on more power tubes just take it to the the shop. Maybe it's something simple. If you can't figure it out, I'd do that before buying the power tubes then finding out that you're powertubes were fine and you wasted the money on them.
#10
Quote by caraluzzo
Did you just put in one new tube?


I did put a new preamp tube.... a 12ax7 in place of a 12at7, and since this happened I switched it back. Yeah I'm going to take it to the shop.....

suck
"After all the practical reason why a majority are permitted to rule is not because they are most likely to be in the right, nor because this seems fairest to the minority, but because they are physically the strongest." -Henry David Thoreau
#11
Sounds like your power tubes went bad.

Taking out preamp tubes when the amp is on standby is a ok. Hell, mesa suggests running the amp with one power tube (not for very long) to test to see which power tube went bad.
I don't give a shit if you listen to me or not
#12
The reason I stated not to change tubes with the amplifier in standby is as follows. When a tube is off, its filament (the part that gloes - and creates the electrons that do the work) is cold and has a lower resistance than when warmed up.

When you turn the amplifier on with the power switch (and in standby) the filaments draw more current than when warmed up. But the power switch is designed to handle the "spike" current when used properly.

If you plug a cold tube into the socket, then the contacts (for the filament) in the socket must tolerate the higher current. If they spark, it can cause corrosion or other damage.

Now, back to the problem. There may be another 12AT7 between the preamp one you changed to a 12AX7. There often are (at least in the many Fender amps I have repaired over time). So look at each tube in pretty dim room light and make sure you can see the dull red glow of the filament in each of them. Turn the amplifier off if you are not sure. You should see the glow disappear.

The EL34 power tubes should also be glowing near the center, but not the large gray structure nearest the glass. If that is glowing red, then there is definitely something wrong with the amplifier, and you will have to take it someplace for service.
#13
You didn't break it by changing a preamp tube. I agree that it sounds like one of the power tubes went south.
I wondered why the frisbee was getting bigger, then it hit me.
#15
GREAT NEWS....IM A MORON! yay...it's working and fine, one of the power tubes had apparently rattled out of the socket ever so slightly. I hadn't touched the power tubes AT ALL, and yet here is this little gap between the pin side of the tube and the socket about .25 cm. I took them both out, pushed them firmly up in there, and TADA!!!

Thanks guys, you were right....power tube prob. The 4 12ax7's are all in working great. The gain structure is definitely enhanced! Now I work on selling this sucker so I can buy me a JCM 800 or a 6505.

ltz,
andy
"After all the practical reason why a majority are permitted to rule is not because they are most likely to be in the right, nor because this seems fairest to the minority, but because they are physically the strongest." -Henry David Thoreau