Russian 6V6's arcing internally

[PlinytheWelder]

I have a Crate Stealth GT-50H head that uses 4 X 6V6 output tubes. When driven heavily, one of the outer tubes will arc over internally. I pulled the outer tubes out and measured B+ at 416V and the bias at -37.6V . This is consistent across all 4 tubes. Also, I had some NOS 6V6's, a GE and a Bendix and put them in the outer sockets and so far they have not arced at all.

The original tubes are SLM "Hot Rods" which I think are Russian and I tried to sub some Russian Reflektor 6V6's that I have a bunch of for times like this.

I am curious as to what's going on here. Do I have a real problem or just crappy tubes?

[tubeswell]

If swapping the tubes stopped the arching, I'd guess it was crappy tubes.

See if the problem persists over the next few days

[Enzo]

And more to the point, it sounds like it was just one tube doing it.

Doesn't mean they are crappy, just means one failed.

The tube probably didn't fail because of voltage or current. It probably failed mechanically.

[PlinytheWelder]

And more to the point, it sounds like it was just one tube doing it.

Doesn't mean they are crappy, just means one failed.

The tube probably didn't fail because of voltage or current. It probably failed mechanically.

No. it was more than one tube and in 2 different sockets. Oh well, so far no more fireworks. Anyway, I guess it time for a new set of output tubes. I was thinking of JJ's or Tung-Sol reissues. I already have new Tung-Sol 12AX7's in the front end and like them just fine. Still, I may try the JJ's first....

[Gtr_tech]

JJs are tough....use those.

[jrfrond]

JJs are tough....use those.

I've seen more JJ's go into meltdown here in our shop than any other 6V6. Every once in awhile, you will see a bad one in the Reflector-branded tubes, but that's just life in modern tube times. I restored a SF Princeton last week with the original RCA 6V6GTA and it still had plenty of balls and life in it.

If you want super tube life, scope out a set of Bendix Red Banks 6992, a steroidal 6V6 that was meant to fly in cruise missles. It might be the last set of power tubes you'll need for that amp.

[Bruce / Mission Amps]

I've seen more JJ's go into meltdown here in our shop than any other 6V6. Every once in awhile, you will see a bad one in the Reflector-branded tubes, but that's just life in modern tube times. I restored a SF Princeton last week with the original RCA 6V6GTA and it still had plenty of balls and life in it.

If you want super tube life, scope out a set of Bendix Red Banks 6992, a steroidal 6V6 that was meant to fly in cruise missles. It might be the last set of power tubes you'll need for that amp.

What cruise missiles use or used vacuum tubes?
And, do you mean a 5992?

[Gtr_tech]

I've always had great luck with JJ pwr tubes so I can't relate. Unless the customer specifies something else the JJs are my go-to.

[PlinytheWelder]

I've seen more JJ's go into meltdown here in our shop than any other 6V6. Every once in awhile, you will see a bad one in the Reflector-branded tubes, but that's just life in modern tube times. I restored a SF Princeton last week with the original RCA 6V6GTA and it still had plenty of balls and life in it.

If you want super tube life, scope out a set of Bendix Red Banks 6992, a steroidal 6V6 that was meant to fly in cruise missles. It might be the last set of power tubes you'll need for that amp.

I forgot about the 5992 Bendix Red Banks. That would be fun! I guess they're not as popular as the 9pin Red Banks that go for $200 each

Hell, I even have a little Red Bank rectifier around here somewhere that would be good for a preamp or something.

From VTV #5
4. 5992
I believe this to be the frst-ever Red Bank electron tube. When it was introduced in May 1952, Bendix called it the "Eclipse-Pioneer" tube. This was because Red Bank Division started out as Eclipse Instrument Company, a maker of aircraft electrical generators in the 1930s. It's hard to find out why Bendix started making tubes there, knowledge was lost over the years and Red Bank Division itself is believed to be defunct.

The 5992 is a 6V6GT with balls. Although rated for 10 watts and 300 volts, its construction is the same kind of wretched excess. So it's probably safe to assume that this tube can take far more than the rated voltage. The pinout is identical to 6V6, so it can be used in 6V6 guitar amps with no changes. Unfortunately, some gurus have found the type in their GE tube manuals, so samples are very hard to find even by Red Bank standards.

Thanks!

[txstrat]

I'd agree with gtr tech.
I built several amps with 6V6 tubes and most often used what was handy.
Last one I built was a deluxe reverb clone and I decided to go for reliable tubes that can handle the voltages and have a decent sound.
I went for JJs "6V6s" (read the review on tubestore.com) and all I can say is "wow". They have a smooth and balanced sound as well as they can stand the bias, that I set to 80%.
I've been playing that amp for 10 months now and no failure so far.

hope this helps

Matt

[jrfrond]

What cruise missiles use or used vacuum tubes?
And, do you mean a 5992?

Yes, that was a typo Bruce.

Actually, the 5992 wasn't meant for cruise missles, but it WAS meant for aircraft. The "cruise missile" tube is the Cetron 6384, which is a friggin' work of art. It works well as a 6L6 and also in place of a 6V6 for people who want more headroom. Read up on it. It's a pretty fantastic tube with SUPERB construction. Sounds super too.

Yeah, the JJ's SOUND good, but I've replaced more screen grid resistors that were on the business-end of JJ 6V6's than you could imagine. I won't even carry them here in the shop.

[HTH]

(to the original poster) were the Russian military 6V6s you used those types sold on ebay with the Russian writing on? if so, the data sheet for those tubes shows a max plate voltage of 250-300v, thats why I've never tried them in a guitar amp.

The Sovtek/EH 6V6s had nice compression on the top end, but are nowhere near as rugged as the JJ 6V6 (or as nice in tone either).

I've been cranking the shit out of the cathode biased 6V6s in my homebrew for over a year now, still sounding great. I seem to remember B+ around 385v, will have to check next time it's open for tinkering.

[PlinytheWelder]

(to the original poster) were the Russian military 6V6s you used those types sold on ebay with the Russian writing on? if so, the data sheet for those tubes shows a max plate voltage of 250-300v, thats why I've never tried them in a guitar amp.

The Sovtek/EH 6V6s had nice compression on the top end, but are nowhere near as rugged as the JJ 6V6 (or as nice in tone either).

I've been cranking the shit out of the cathode biased 6V6s in my homebrew for over a year now, still sounding great. I seem to remember B+ around 385v, will have to check next time it's open for tinkering.

Yeah, they were ebay tubes at about $3 each. But, the first tube that did it were the original SLM/Crate branded tube that probably came with the amp. I have the Lee Jackson service DVD and in it he mentions that the original early '90s tube were Russian from the factory.

In looking at the data sheets for NOS 6V6's, max plate voltage is 350V, but they are routinely used at more in guitar amps. The cyrillic 6V6's can't

The 5992 can probably take way more.
http://lib.store.yahoo.net/lib/thetubestore/5992.pdf

[Nihilist]

I've been using the Russian Reflektor tubes (bought from Ebay) for almost 2 years now in a home "hifi" rig. They are driven by a 6AN8 (triode strapped) , and the "6V6's" are in a triode strapped , push-pull setup.

I have 405V on the plates and a Cathode bias of 30 Volts. This puts the 6P6S's (Russian designation) at 11.25W dissapation , or about 85% of their rated 13.2 watt max. BTW, the spec sheet I have shows them to have a Plate Voltage of 350 and a Grid-2 Voltage of 315 . I am running Grid-2 in parallel with the Plate (with a wire, not a resistor) for triode mode.

These sound awesome, have performed flawlessly , and SMOKE a set of vintage Magnavox 6V6GT's I have in terms of clarity and output. The Maggies perhaps have a little more midrange presence, but the bass is BLOATED and they fall on their face far before the Reflektors.

I am really quite surprised by all the negative threads I've read about the Reflektor tubes not handling the voltage/power of guitar amps. They've served me well for about 2 years, and I don't listen to smooth jazz. Manowar, Megadeth, Motorhead, COC , Pantera , Slayer, Morbid Angel , etc. , plus various blues bands is what I listen to.

Maybe you guys got old , used up tubes. Did you get matched tubes, or match them yourself before using ? Did you rebias your amp ? I dunno what to think. I guess I should be happy, the less of you guitar guys that like them means there will be more for me !

Here's a pic of my setup :

http://img101.imageshack.us/img101/5...9aarevizj4.png

http://img101.imageshack.us/img101/7...pplyforfn4.png


................................Blake

[rockon1]

JJs are tough....use those.

Got to agree. The JJ's are rated for 500PV and 450 on the screens. Ran them in my Supersonic at 470volts and currently in my Rivera at 430+volts no problems . Bob