High V 6L6 Type Tube

[MikeMurray]

Hey guys

So I've built a champ that runs a bit high on the B+ (Quite rediculously) so basically I am looking for a 6L6GC / WXT+ / KT66 type tube that can handle as much voltage as possible.

Anyone got suggestions? I'm not looking for NOS or anything so they must be reasonably priced.

Cheers
Mike

 

[celeste]

807's can handle 1200v, you have to add plate caps and that makes a lot of people nervous.

 

[eugenedunn]

How much B+ you talkin' bout?

6L6's are about 500, KT66's around 550 or so..... KT77's and EL34's can go up to even 700-800 I think.....

 

[muchxs]

Ah-HAH! I didn't expect to find a use for my 6BG6G so soon...

"The 6BG6G is essentially a mechanical redesign of type 6L6G to permit operation as a horizontal deflection amplifier for television service."

That means it's a common tube in black and white television sets.

"It uses a top cap connection and additional insulation for the plate structure to withstand the high peak plate voltage encountered in such circuits".

High plate voltage: They mean 6600 volts surge. Max DC plate supply is 700 volts.

 

[stingray_65]

OK
so how high? (B+ to plate)

What type of OT are you using? Most champ Ot's I've seen were a bit small in my opinion, but thats part of the snarl a champ has. using a 6v6 with a decent supply voltage maight make for a short lived OT

what is your PT's seconday current rated at? 6L6 = 80 mA current while a 6V6GT = 35 mA drawn (rough numbers)

I'm not saying don't try it, I've done it myself many times and been real Happy

Just know how your affecting your amp.

 

[MikeMurray]

490 or so on the B+... I suppose to run a 6L6 at that voltage I'll have to rebias? (Cathode biased champ)

 

[stingray_65]

Ah-HAH! I didn't expect to find a use for my 6BG6G so soon...

"The 6BG6G is essentially a mechanical redesign of type 6L6G to permit operation as a horizontal deflection amplifier for television service. It uses a top cap connection and additional insulation for the plate structure to withstand the high peak plate voltage encountered in such circuits".

got basket full of them 6BG6GC's and been waiting to find some Iron to make something REAL loud!

 

[stingray_65]

OK
NOW WAIT A MINUTE!
how come your B+ is ridiculously high?
something is amiss here.

 

[MikeMurray]

The dam idiot that wound the transformer screwed up And now he's not answering my mails.

Running sag resistors atm to lower voltage to 420 which is working for now (With a 6L6) but thought hey why not see what'd happen if I could run it without em

 

[stingray_65]

most 6L6's will live in that range (<500VDC)

but again why so high?

if its a scratch build with Iron you had lying around, I understand the use what you got mentality, But if it's a purchased PT made for a Champ I would be looking at fixing the issue.

single ended cathode biased you want about 500 ohms and I would use 5 watt minimum ( 250 ohms for P-P)

 

[MikeMurray]

The PT was already spec'd a little high (350 volts) but it's actually pushing out about 405v.. And once that's gets rectified it pushes around 450v (was even more unreasonable running a GZ34 like what was sent with the kit) I suppose this is what happens when you deal with some guy in the bundoo's of South Africa winding in his garage.

 

[muchxs]

490 or so on the B+... I suppose to run a 6L6 at that voltage I'll have to rebias? (Cathode biased champ)

A 6L6GC will work o.k. with a stock "Champ" 470 ohm cathode resistor in your amp.

got basket full of them 6BG6GC's and been waiting to find some Iron to make something REAL loud!

Yeah, but... remember they only dissipate approx. the same wattage as an old 6L6G. Around 19 watts. 6L6GCs dissipate around 30 watts. Just for fun shoot for power output in excess (much XS! ) of dissipation and see what happens.

 

[celeste]

Ah-HAH! I didn't expect to find a use for my 6BG6G so soon...

"The 6BG6G is essentially a mechanical redesign of type 6L6G to permit operation as a horizontal deflection amplifier for television service."

That means it's a common tube in black and white television sets.

"It uses a top cap connection and additional insulation for the plate structure to withstand the high peak plate voltage encountered in such circuits".

High plate voltage: They mean 6600 volts surge. Max DC plate supply is 700 volts.

Yep, it it the link between the 6L6 and the 807. The 807 takes a 6BG6 and makes a real transmitter tube out of it.

There is a maximum voltage you can put through an octal base because the pins are so close together if yoiu get to high, you risk arching, so yo have to go top cap.

 

[stingray_65]

The dam idiot that wound the transformer screwed up And now he's not answering my mails.

Running sag resistors atm to lower voltage to 420 which is working for now (With a 6L6) but thought hey why not see what'd happen if I could run it without em

I have always disliked sag resitors, a patch at best.

If the tranny is wound to that voltage try the 6L6 and keep a monitor on your Power trans and OT
they will get warm, but not so hot you cant hold your hand on them.

use your nose too, you smell anything funny shut her down

OH!

what's your filter caps rated for?

will you be able to change out the first dropping resitor to keep the rest of the circuit at a sane level?

 

[Wally]

The Jim Kelley FACS amps from the '70's run 4 6V6's with 485 volts on the plates?????
Almost any modern 6v6 amp runs plate voltages that are far above the stated parameters for a 6V6. The same holds true for EL-84/6BQ5's. The 6v6 and the EL-84 both have max voltages specified at something like 285-325 volts don't they? How have these tubes survivied in our guitar amps that run in the high 300's at a minimum and a fair amount over that in DR's. That is not even mentioning the Jim KElly. I know of a Jim KElley that just keeps on 'abusing' those 6V6's without ever having a failure. How do they do that?
At one time, the modern production 6V6's were not up to the task in even a DR. JJ's will handle your voltages, I am going to think. The Sovtek tung=sols might, too, I would think. NOS tubes are expensive, but if they would hold up in the Kelley amp, they will handle that 490v.
Just sayin' .....

 

[MikeMurray]

I have always disliked sag resitors, a patch at best.

Agreed man... First amp build so kind of had to rely on the guy that was supplying me. Bloody idiot.

If the tranny is wound to that voltage try the 6L6 and keep a monitor on your Power trans and OT
they will get warm, but not so hot you cant hold your hand on them.

use your nose too, you smell anything funny shut her down

Transformers don't get hot, well PT warms up a touch but only nice to warm hands up in the cold

OH!

what's your filter caps rated for?

will you be able to change out the first dropping resitor to keep the rest of the circuit at a sane level?

Hmmm!!! first stage is 40uF (Pushing that 5y3GT) But rated for 600V.. That sounds like a pretty good idea

 

[stingray_65]

600V rating is marginal, only a 20% saftey net,

it should work though.

 

[muchxs]

The Jim Kelley FACS amps from the '70's run 4 6V6's with 485 volts on the plates?????

Jim Kelley obviously designed the FACS as a torture chamber for 6V6s. It's pretty easy to find 6V6s that arc in amps with 100 volts less on the plates than your Kelley.

S.A. Mike is running high voltage in a "Champ" type amp. That means the one PA tube amplifies the full swing of the signal. Your Kelley is AB, that means the tubes get a little rest for part of the cycle. That's the purpose of Class AB, higher power output within the dissipation limits of the tubes.

6V6s Class A with a 490v plate supply? Dude's lucky they don't melt!

 

[MikeMurray]

I also considered running a 5H choke in front of it, might take a touch off the voltages as well - enough for a bit more safety?

I see I can get 4H 90mA chokes from TubeDepot (Where I usually get stuff) would that work with a 5y3gt?

 

[muchxs]

I also considered running a 5H choke in front of it, might take a touch off the voltages as well - enough for a bit more safety?

You've had that amp running for what, a month? And it hasn't burned a hole in the floor yet?!

Seriously, we went over this. Your supply voltage is way high for 6V6 but you haven't blowed it up yet. That's "destructive testing", so far you've failed to destroy it so it must be built pretty good. Swap in a 6L6 to deal with your high voltage and maybe track down a 5U4G to drop more voltage than your 5AR4. If you're still running a 22k resistor in the dropping string to the preamp double that up, use say a 47k.

If the thing isn't setting the carpet on fire or blowing the stuffing out of the filter caps you may be o.k..

Keep a fire extinguisher close at hand.

Rumor has it you play barefoot with your toes inches from your amp. You're a braver man than I.