Flashing EL34

electropt · 24th June 2004, 06:48 PM

Hi,

I have a Class AB push-pull integrated amp with 4 EL34 on the output stage. One of them in some music passages flashes a lot! I came to the conclusion that it should be on its way out and already ordered a mached quad of SED EL34.

My question is this, is it normal to a tube die this way? I guess it was defective since day one, from the first time I used this set of tubes one of them flashed very faintly, but now... WOW!

I made a video of the flashing tube, its here.

Only one of the four glows like this, the other of the same channel only blinks slightly, I guess due to the current drawn of the other tube.

How about the SED EL34 (Svetlana old factory tubes now with the =C= logo), are they any good?

Thanks in advance.

Hugo

kevin gilmore · 24th June 2004, 10:10 PM

Sure looks like a cathode to heater short of some kind...

Jax · 27th June 2004, 05:10 PM

It seems to me to be the screen grid that is flashing. It's not normal, there should never be an orange flashing during operation.

Why this happens is difficult to diagnose without a schematic but the most common cause for this flashing is a way too high voltage on the screens. I've seen it myself when I ran the screens at 430V in a pentode circuit.

By all means, try a new quad but if you see flashing, turn off and have the amp investigated.

benny · 27th June 2004, 05:13 PM

really, i have no idea... what voltages are you using???

you maybe have a too high a screen voltage and there is arcing or something ocouring... my guess is at the too high a voltage.

cheers

EDIT: oh well, that was a lot of using saying the same kind of thing as what jax just said...

Sch3mat1c · 27th June 2004, 11:03 PM

I have a 6V6GT that sorta does that. It glows brighter than most, probably a broken screen wire or something. Never seen it vary in the SE amp it was in though.

Also had a 6L6GC from Valve Art that smoked a screen wire or something, it was running within limits (right on max. voltage, but 6L6s have been treated worse so I'm not sweating that). Still works fine to this date, AFAIK...

Tim

karma · 28th June 2004, 01:16 AM

my amp did the same thing. cheaper to replace the quad
than to leave it like i did. 2 weeks ago my amp finally died. only would have cost me $60 for new tubes now its $200 for part's and tube's

you shoulds see it when it really short's

could this happen it could or maybe not see pic

>>Svetlana old factory tubes now with the =C= logo anygood?<<

i was looking at this type allso with the gold pins. not sure if there good. still need to pic them up

Sch3mat1c · 28th June 2004, 06:58 AM

Long as we're posting blue glow shots, here's some of the GOOD kind.

- Revision 3 with Sylvania 6L6GC and JAN-CRC 6L6GA respectively. No wait... that must be the 6F6.

Tim

karma · 28th June 2004, 07:26 AM

nice here's one of mine not blue but not of the bad kind

Sch3mat1c · 28th June 2004, 09:28 AM

Purpley, looks more like gas to me.. ?

Tim

Duo · 28th June 2004, 09:32 AM

haha, that's definitely arcing.

I have a tube tester here on which if you press the incorrect button with 6AL5 in, you get a very nice bright arc like that, and the tube is fried.

24th June 2004, 06:48 PM	#1
electropt diyAudio Member Join Date: Jun 2004 Location: Lisboa	Flashing EL34 Hi, I have a Class AB push-pull integrated amp with 4 EL34 on the output stage. One of them in some music passages flashes a lot! I came to the conclusion that it should be on its way out and already ordered a mached quad of SED EL34. My question is this, is it normal to a tube die this way? I guess it was defective since day one, from the first time I used this set of tubes one of them flashed very faintly, but now... WOW! I made a video of the flashing tube, its here. Only one of the four glows like this, the other of the same channel only blinks slightly, I guess due to the current drawn of the other tube. How about the SED EL34 (Svetlana old factory tubes now with the =C= logo), are they any good? Thanks in advance. Hugo

27th June 2004, 05:10 PM	#3
Jax diyAudio Member Join Date: Nov 2003 Location: South Sweden	It seems to me to be the screen grid that is flashing. It's not normal, there should never be an orange flashing during operation. Why this happens is difficult to diagnose without a schematic but the most common cause for this flashing is a way too high voltage on the screens. I've seen it myself when I ran the screens at 430V in a pentode circuit. By all means, try a new quad but if you see flashing, turn off and have the amp investigated. __________________ Jan

27th June 2004, 11:03 PM	#5
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	I have a 6V6GT that sorta does that. It glows brighter than most, probably a broken screen wire or something. Never seen it vary in the SE amp it was in though. Also had a 6L6GC from Valve Art that smoked a screen wire or something, it was running within limits (right on max. voltage, but 6L6s have been treated worse so I'm not sweating that). Still works fine to this date, AFAIK... Tim __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"

28th June 2004, 06:58 AM	#7
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	Long as we're posting blue glow shots, here's some of the GOOD kind. - Revision 3 with Sylvania 6L6GC and JAN-CRC 6L6GA respectively. No wait... that must be the 6F6. Tim __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"

28th June 2004, 09:28 AM	#9
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	Purpley, looks more like gas to me.. ? Tim __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"

24th June 2004, 10:10 PM	#2
kevin gilmore diyAudio Member Join Date: May 2002 Location: wheeling illinois	Sure looks like a cathode to heater short of some kind...

27th June 2004, 05:13 PM	#4
benny diyAudio Member Join Date: May 2004 Location: Melbourne, Australia	really, i have no idea... what voltages are you using??? you maybe have a too high a screen voltage and there is arcing or something ocouring... my guess is at the too high a voltage. cheers EDIT: oh well, that was a lot of using saying the same kind of thing as what jax just said...

28th June 2004, 09:32 AM	#10
Duo diyAudio Member Join Date: Jun 2002 Location: Victoria, BC, Canada	haha, that's definitely arcing. I have a tube tester here on which if you press the incorrect button with 6AL5 in, you get a very nice bright arc like that, and the tube is fried. __________________ -- Duo, W1ngs, VA7MON, and lesser known handles. -- -- http://www.w1ngselectronics.com -- My Work and Projects --

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