Tube amp guru's....help

[Superlizard]

Are the t00b sockets PCB mounted?

If so, not a good thing.  There have been many cases of faulty PCB-mounted t00b sockets... just not a stable t00b platform.

I lean towards OzziePete's synopsis - it's prolly a waste of time, cuz the $$$ spent repairing it
is prolly gonna be more than you paid for it.

 

[DangerousR6]

The toobs are mounted to their own board, not on the main PCB...

 

[Superlizard]

The toobs are mounted to their own board, not on the main PCB...

Still, they're PCB mounted (now that I've had time to scan above photo).

Said PCB may even be a few layers.

Pulling out t00bs or slapping them in - you're putting stress on the circuit board.



The far better design is the old-school way of mounting the t00b socket
right on to the chassis (as below):

 

[OzziePete]

The toobs are mounted to their own board, not on the main PCB...

Still, they're PCB mounted (now that I've had time to scan above photo).

Said PCB may even be a few layers.

Pulling out t00bs or slapping them in - you're putting stress on the circuit board.



The far better design is the old-school way of mounting the t00b socket
right on to the chassis (as below):

Doesn't matter if it's point to point/chassis or PCB mounted, you have to hope there's quality engineered into the build so the amp will last lots of tube changes and take the heat of all that work.

 

[-CB-]

The pinouts for EL34s and 6L6s (as well as a few others such as 5881s and KT77s) are all the same, so it's not like you're going to blow anything up.

Not true !  Check again!!

EL34

6L6 pinout

Pin 1 on the EL34 is the supressor grid, left blank (tied internally) on the 6L6

!~~~~!

The 1/4 amp fuses connect to the cathodes, lifting them from ground when they blow.

There IS an adjustable bias supply (just look for the trim pot on the power supply schematic)

I'd not use EL34's in there.... not gonna work, its made for 6L6's - according to the schematic posted.

Then you say - the combo is different... dunno.

Try running it with no output tubes, and see if the fuses go.  Try one tube in a socket at a time, faulty tube. 

 

[Superlizard]

Doesn't matter if it's point to point/chassis or PCB mounted, you have to hope there's quality engineered into the build so the amp will last lots of tube changes and take the heat of all that work.

True, said engineering should be built into those PCB amps.

But the inherent design does not elicit said confidence as would old-school chassis-mounted sockets with flying leads.

In all this, I'm not saying this is the particular case as to his amp issues, but it could be.

For future consideration, I'd avoid PCB mounted t00b amps like the plague - they have a history, and a sordid one at that.

 

[Superlizard]

Not true !  Check again!!

EL34

6L6 pinout

Pin 1 on the EL34 is the supressor grid, left blank (tied internally) on the 6L6

!~~~~!

The 1/4 amp fuses connect to the cathodes, lifting them from ground when they blow.

There IS an adjustable bias supply (just look for the trim pot on the power supply schematic)

I'd not use EL34's in there.... not gonna work, its made for 6L6's - according to the schematic posted.

Then you say - the combo is different... dunno.

Try running it with no output tubes, and see if the fuses go.  Try one tube in a socket at a time, faulty tube.  

I'm lost in all the text in this thread here... what PTs are this amp designed for?  I assumed he bought it with EL34s... then again,
maybe he bought it used and someone loaded (incorrectly) EL34s.  Maybe it *is* 6L6s after all...

Either way, as I surmised previously, can't just swap 'em without modifications.

 

[Cagey]

Either way, as I surmised previously, can't just swap 'em without modifications.

Depends on the amp design. I have a Carvin TS100 stereo power amp that will let you plug in either 6L6s, 5881s or EL34s without modification. In fact, you theoretically don't even need to rebias it - there's a little internal switch to select which bias level to use depending on the tubes installed.

 

[DangerousR6]

Not true !  Check again!!

EL34

6L6 pinout

Pin 1 on the EL34 is the supressor grid, left blank (tied internally) on the 6L6

!~~~~!

The 1/4 amp fuses connect to the cathodes, lifting them from ground when they blow.

There IS an adjustable bias supply (just look for the trim pot on the power supply schematic)

I'd not use EL34's in there.... not gonna work, its made for 6L6's - according to the schematic posted.

Then you say - the combo is different... dunno.

Try running it with no output tubes, and see if the fuses go.  Try one tube in a socket at a time, faulty tube.  

I'm lost in all the text in this thread here... what PTs are this amp designed for?  I assumed he bought it with EL34s... then again,
maybe he bought it used and someone loaded (incorrectly) EL34s.  Maybe it *is* 6L6s after all...

Either way, as I surmised previously, can't just swap 'em without modifications.

I believe Crate says the BV 6212 comes standard with 6L6's, I bought it used and someone had changed the tubes to EL34's..

The pinouts for EL34s and 6L6s (as well as a few others such as 5881s and KT77s) are all the same, so it's not like you're going to blow anything up.

Not true !  Check again!!

EL34

6L6 pinout

Pin 1 on the EL34 is the supressor grid, left blank (tied internally) on the 6L6

!~~~~!

The 1/4 amp fuses connect to the cathodes, lifting them from ground when they blow.

There IS an adjustable bias supply (just look for the trim pot on the power supply schematic)

I'd not use EL34's in there.... not gonna work, its made for 6L6's - according to the schematic posted.

Then you say - the combo is different... dunno.

Try running it with no output tubes, and see if the fuses go.  Try one tube in a socket at a time, faulty tube.  

There is no bias adjustment on the combo, there is on the head version but NOT the combo...I'm assuming it's a "cathode" bias amp.... :dontknow:

 

[Superlizard]

I believe Crate says the BV 6212 comes standard with 6L6's, I bought it used and someone had changed the tubes to EL34's..

Hmm...

And you said you tried 6L6s with the same crappy result as the EL34s?

Also, did the seller tell you if it was modded in any way?

Has it *always* functioned like this since you bought it?

This could simply be a case of dumbass - where original ignorant owner slapped EL34s in it without thinking (sounds
like it's s'posed to take 6L6s) and fried something on the PCB... then decided to try to sell it off... to you.

 

[Death by Uberschall]

I think it's just the Crate Blue Voodoo Blues.

I used to play with another guitar player that was in one of my earlier bands. He had a Blue Voodoo combo that stayed in the shop or on it's way back to Crate more than he played it. Something is just not right with them, whether it's poor solder joints, bad design, what ever. That's why I recommended the bon fire.

 

[DangerousR6]

I believe Crate says the BV 6212 comes standard with 6L6's, I bought it used and someone had changed the tubes to EL34's..

Hmm...

And you said you tried 6L6s with the same crappy result as the EL34s?

Also, did the seller tell you if it was modded in any way?

Has it *always* functioned like this since you bought it?

This could simply be a case of dumbass - where original ignorant owner slapped EL34s in it without thinking (sounds
like it's s'posed to take 6L6s) and fried something on the PCB... then decided to try to sell it off... to you.

That's quite possible, I was on the sucker end of the deal...But unfortunately he mentioned nothing of any mods to the PCB...

I think it's just the Crate Blue Voodoo Blues.

I used to play with another guitar player that was in one of my earlier bands. He had a Blue Voodoo combo that stayed in the shop or on it's way back to Crate more than he played it. Something is just not right with them, whether it's poor solder joints, bad design, what ever. That's why I recommended the bon fire.

Well the cabinet is still good, if I'm unable to get it fixed, then I can still make an extention cab out of it... :dontknow:

 

[-CB-]

There is no bias adjustment on the combo, there is on the head version but NOT the combo...I'm assuming it's a "cathode" bias amp.... :dontknow:

No its not cathode bias... higher power push-pull amps dont do well with cathode bias.  Reason being is - either they run push-pull class A, keeping a constant cathode current (more or less), or...  the cathode current runs all over the place because the tube is running class A/B with low idle current, and high playing current.  When you try to get volume, the current goes up, the relationship of the cathode to ground (and control grid) changes, altering the bias.  Doesn't really work too well on larger amps.  Doing it on a 12w or 15w tweed Deluxe was one thing, on a 2x6L6 amp at 40 or 50 watts... quite another, unless you run some huge iron to handle the class A operation, but why do that when you can just bias it via the grid and make it work even better?

So, it may have a non-adjustable bias, still grid biased, or... ewwwww... some hybrid terrible grid/cathode self balancing bias scheme that Fender used in the dread silverface amps.  Nah, I'm guessing just non adjustable grid bias.  The amp MAY be made for both EL34 and 6L6, but my response was "the pinouts are different" and they are.

 

[-CB-]

Again, run it with no output tubes... see if the fuses hold, they ought to!

Then run it with some 6L6's and your problem may be solved.  Borrow some 6L6's.. .could be those supressor grids are "gone" in the EL34's.  You run EL34's in a Fender and they fry, taking out screen grid resistors too.  Thats because Fender used the "unused" socket (#1) as a holder for the grid snubber resistor (pin 1 to 5 connection with a 1.5kohm 2w resistor).  They also used the unused pin #6 as the holder for the screen grid resistor (pin 4 to 6, around the socket with a 470ohm 5w resistor).

The amp can be fixed to play just fine.... dont do anything drastic.

 

[DangerousR6]

Again, run it with no output tubes... see if the fuses hold, they ought to!

Then run it with some 6L6's and your problem may be solved.   Borrow some 6L6's.. .could be those supressor grids are "gone" in the EL34's.  You run EL34's in a Fender and they fry, taking out screen grid resistors too.  Thats because Fender used the "unused" socket (#1) as a holder for the grid snubber resistor (pin 1 to 5 connection with a 1.5kohm 2w resistor).  They also used the unused pin #6 as the holder for the screen grid resistor (pin 4 to 6, around the socket with a 470ohm 5w resistor).

The amp can be fixed to play just fine.... dont do anything drastic.

I have both a set of Tung-Sol 6L6's and some JJ EL34's, I'll try ti without the tubes and see if the fuse holds...

 

[DangerousR6]

O.k., did the no power tube test, and the fuse stayed in tact. So I'm assuming that my transformer is good, so I suspect this narrows the problem to the power tube area.... :dontknow:

 

[DangerousR6]

The Blue VooDoo has risen from the depths of turdville to be polished back into a diamond....In the imortal words of Dr. Frankenstien, that's "Frrrrrraunkinsteen"....

I fixed it.... :hello2:

I got a video, but I'vent got the right hook up to my computer yet.... :sad1:

 

[Cagey]

I fixed it.... :hello2:

I got a video, but I'vent got the right hook up to my computer yet.... :sad1:

So... which tool did you use, the Glock or the Ruger?

 

[Superlizard]

The Blue VooDoo has risen from the depths of turdville to be polished back into a diamond....In the imortal words of Dr. Frankenstien, that's "Frrrrrraunkinsteen"....

I fixed it.... :hello2:

I got a video, but I'vent got the right hook up to my computer yet.... :sad1:

:icon_scratch:  Lots of duct tape?  :icon_scratch:

 

[DangerousR6]

I fixed it.... :hello2:

I got a video, but I'vent got the right hook up to my computer yet.... :sad1:

So... which tool did you use, the Glock or the Ruger?

I don't like glocks and I don't have a ruger....I used an AR-15.....j/k

The Blue VooDoo has risen from the depths of turdville to be polished back into a diamond....In the imortal words of Dr. Frankenstien, that's "Frrrrrraunkinsteen"....

I fixed it.... :hello2:

I got a video, but I'vent got the right hook up to my computer yet.... :sad1:

:icon_scratch:  Lots of duct tape?  :icon_scratch:

If I needed it to go 100 MPH, I'd have used duct tape..

I did the test of the fuse without the tubes, and it didn't blow the fuse. So I went back and started looking for the obvious, found several wires that the terminals were corroded and 2 of those were just barely hanging on. So I cleaned the terminals, secured all the connections back down. Put the tubes in and viola....It works...