Flashing EL34

[electropt]

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]

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

 

[Jax]

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]

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]

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]

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]

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

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

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

Tim

 

[karma]

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

 

[Sch3mat1c]

Purpley, looks more like gas to me.. ?

Tim

 

[Duo]

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.

 

[karma]

ok here's one with the light on working on a power supply
for the filament

there new out of the box

gas? i have just a little

 

[electropt]

Hi,

The tubes I have right now are Ei Yugo, they are not very well rated... The amp I have them on is a Jadis Orchestra, my first and last comertial tube amp, the next one will be DIY

The SED EL34 and some other are for sale at eBay, I got my matched quads for US$58.90 including shipping for anywere in the world from this auction here but not the gold pin ones...

Here is a pic of my quite nice sounding amp:

An externally hosted image should be here but it was not working when we last tested it.

The rest of the system: Monitor Audio Studio 6, AMC CDM7 (CDP with CDM4 transport and modular output modules), Rega Planet 3, Rega Eos phono stage, Straight Wire Maestro ICs, and Cable Talk 3.1 speaker cable (to be upgraded SOON!).

 

[Tube_Dude]

Olá electropt!

Have you remarked ,that the Jadis Orchestra has a transistor gain stage at the input and if you take it out of circuit the sound become much better.

The Jadis Orchestra is in fact a hibrid amp...

Um abraço

 

[electropt]

Caro Jorge,

Obrigado pela dica, tenho de ver essa situacao. Ja teve a oportunidade de comprovar o efeito antes/depois?

Cumprimentos,

Hugo

---------------------------------------------------------------------------

Dear Jorge,

Thanks for your tip, I have to take a look at it. Have you had the oportunity to hear the result of such mod?

Best regards,

Hugo

 

[Tube_Dude]

Dear Jorge,

Thanks for your tip, I have to take a look at it. Have you had the oportunity to hear the result of such mod?

Yes...i have one of this babys. The sound inproved a lot.
Specially the perceived dinamic range.

Um abraço

PS: Se quiseres contacta-me por mail.

 

[electropt]

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

Hi,

It is comforting to know that the two pairs of power tubes are protected from arcing or over-bias operation by two .315mA fuses mounted inside the chassis.

 

[electropt]

Dear Sir,
Thank you for your interest in our products.
The Orchestra is a hibrid. The preamp part is solid state.
Cordially,
Jadis
----- Original Message -----
From: Electro PT
To: jadis@jadis-electronics.com
Sent: Tuesday, June 29, 2004 2:49 AM
Subject: Jadis Orchestra


Dear Sirs,

Could you please tell me if the Jadis Orchestra integrated amplifier is a hibrid or all tube?

Thanks in advance.

Kind regards,

Hugo




Shame on Jadis!!!

I never read in the catalog that it was a hibrid... Jadis is no more!

Bahhhhhhhhhh

 

[karma]

ahh u still got a nice amp just mod it

 

[fdegrove]

Hi,

I never read in the catalog that it was a hibrid... Jadis is no more!

Hybrid?
I don't think so....Unless they changed it recently all the JA Orchestras I've seen so far had no semi-conductors in the direct signal path whatsoever.

The way it is setup is 1/2 12AX7A as a voltage amp, followed by the other 1/2 12AX7A as a phasesplitter/driver for the PP EL34 or KT90s for the Reference models.

BTW, as it is fully P2P wired except for some parts of the PS, tracing the signal path is pretty straightforward.

Cheers,

 

[electropt]

Hi,



Hybrid?
I don't think so....Unless they changed it recently all the JA Orchestras I've seen so far had no semi-conductors in the direct signal path whatsoever.

Fdegrove, unfortunatly for me, you are wrong. In the PCB where you have the volume and balance blue Alps pots you also have two 2N1711 transistors in the signal path as Tube_Dude said.

An externally hosted image should be here but it was not working when we last tested it.

And I guess the actual production units still are hibrid based on the repply I got from Jadis. Mine was from early 1998 (SN: 0770).

The way it is setup is 1/2 12AX7A as a voltage amp, followed by the other 1/2 12AX7A as a phasesplitter/driver for the PP EL34 or KT90s for the Reference models.

BTW, as it is fully P2P wired except for some parts of the PS, tracing the signal path is pretty straightforward.

It has a very nice P2P construction and simple wire scheme.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

It has PCBs in the HV power supply in the source selector and in the volume/balance/input gain stage.

I guess its almost a Jadis

Cheers,

Hugo

PS. The lousy pictures were made with a crapy CMOS camera, please take that into consideration. Or else you can give me a new good one