EVH 5150 III, change from 6l6GC to EL34?

[Rod]

HI!

Is it possible to change te 6lGGC tubes that comes stock wih the amp to El34?

What componentes in the poweramp must be changed?

[Enzo]

The short list?

Each EL34 needs an additional 0.6A heater current, so all four new tubes would need 2.4A extra current. You need to test the power transformer to see if it can handle that.

The screen resistors need to change from 100 ohm to 1k ohm 5 watt.

The bias is set up to center around -60v. EL34 will probably want closer to -45v or -50v. You'd need to modify the bias supply.

And most important, 6L6 does not use pin 1 and often uses the place to wire a resistor to the control grid. But the EL34 DOES use pin 1, it is the suppressor grid and must be wired to the cathode, pin 8. So you need to very carefully explore the copper trace work under the power tube sockets with an eye to modifying it as needed for that.

[Jazz P Bass]

Nice concise answer, Enzo.

I forgot about the pin 1 thingy.

[alexradium]

There is also an EL34 EVH version out,so i guess the original amp was designed to accomodate various tubes.
I would be more corncerned about choosing a tube that stands high voltage on screens,Peaveys were on 520V,don't know about this,or at least reducing it with a VVr.

[Enzo]

Peavey made an EL34 version of the 5150, but they had to make a new power tube board to do it.

But the OP has an EVH5150 III, which is a Fender product.

[g1]

For the new 5150III, there are EL34 versions in both 50W and 100W.
I don't know if they use different transformers to handle the extra heater current or not. I would not try changing without verifying if the transformer can handle it. It's possible the power tube board is different also.
Ideally, you would want to compare the schematic and parts list for both the 6L6 and the EL34 versions.

[J M Fahey]

Short answer: I wouldn´t Mod, period.
Can of worms.

That, without missing the main point: Customer might not like the new sound.
*After* the job is made, of course.

[The Dude]

^^^^^^ I agree. And, to what end? What is the purpose of the mod? The EVH 5150 "sound" comes primarily from the preamp. I doubt this conversion would have much effect on tone.

[cerrem]

I know xxxx at Fender that did design the amp and the recent change over to EL34.... He mentioned that the transformers were not changed.. He wanted to change the OT but was forced to keep it on place for cost reasons and management issues... The PT works fine with EL34's no significant temperature rise.. They issue he had to work out was reducing gain in the second stage from over loading the EL34 inputs...