I Have A Tube Flash

Fred

Well-Known Member
May 31, 2010
296
5
365
Covington, LA
Last night I replaced the stock Electro-Harmonix 12AT7 driver tubes in my Jolida 502 with a matched pair of Telefunken's. One of the Tele's flashes a very bright white at power up. The tube then glows its normal red and seems fine in all respects. I have heard that the Mullards are notorious flashers, but I have never had a tube do this much less a good Telefunken. So my question: Should I be worried? Is this considered normal for some tubes? The flash appears to come from the base of the tube, but light can be tricky paricularly to the naked eye, and that observation cannot be considered etched in stone.

I'd welcome comments on this please.
 

Fred

Well-Known Member
May 31, 2010
296
5
365
Covington, LA
Hi Steve,

I do not have a tube tester and the system sounds fine. My concern is if the flash indicates a problem with the tube. I just bought this pair and would be inclined to contact the seller for a refund or replacement if the flashing is an indication that the the tube life may be compromised.
 

cjfrbw

Well-Known Member
Apr 20, 2010
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IF the flash is unilateral, then it could be a gassy tube and would need to be replaced. Mullard flash would be bilateral in both channels, and is not really a bright white flash, more of a surge illumination.
 

MylesBAstor

Well-Known Member
Apr 20, 2010
11,236
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New York City
Last night I replaced the stock Electro-Harmonix 12AT7 driver tubes in my Jolida 502 with a matched pair of Telefunken's. One of the Tele's flashes a very bright white at power up. The tube then glows its normal red and seems fine in all respects. I have heard that the Mullards are notorious flashers, but I have never had a tube do this much less a good Telefunken. So my question: Should I be worried? Is this considered normal for some tubes? The flash appears to come from the base of the tube, but light can be tricky paricularly to the naked eye, and that observation cannot be considered etched in stone.

I'd welcome comments on this please.

Are you sure it's a real authentic Telefunken? Does the flashing tube have a diamond underneath?
 

mep

Member Sponsor & WBF Founding Member
Apr 20, 2010
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Relax boys and girls. European small signal tubes are known to flash upon turn-on. It is nothing to worry about.
 

cjfrbw

Well-Known Member
Apr 20, 2010
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Pleasanton, CA
Buy it a trench coat and keep it away from women and children?
 

MylesBAstor

Well-Known Member
Apr 20, 2010
11,236
81
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New York City
Not all Teles have diamonds on the bottom. My ECC803S

803s might be the exception? Personally thought all Teles had a diamond. Saw one of the tube places (tubedepot?) had some ECC803s for sale for around $1300 each (I think they had five).

Even having a doesn't necessarily ensure they might not be counterfeit E. German tubes, etc according to some sources. I always thought Teles without diamonds on the bottom were from a variety of sources like Siemens etc (not unlike tube of your where manufacturers made tubes for each other).

The only tubes that I have that "flash" are either Mullard or Ei 12Ax7/ECC83s. None of my Tele ECC83s, Amperexes, etc flash.
 

Fred

Well-Known Member
May 31, 2010
296
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365
Covington, LA
Are you sure it's a real authentic Telefunken? Does the flashing tube have a diamond underneath?


Yes they do sport the diamond imprint on the bottom.


Relax boys and girls. European small signal tubes are known to flash upon turn-on. It is nothing to worry about.

I really want to believe that. Is there a particular reason or part of the tubes design that accounts for this?
 

mep

Member Sponsor & WBF Founding Member
Apr 20, 2010
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Hi Fred,

The filament of the tube is what flashes. The color it gives off is also dependent on the heat produced by the electical charge passing through it. More charge passes though at turn on, when the filament is cold (the resistance is least).

My advice, you will never be happy until you replace that tube man!

Tom

Please send all European tubes that flash to me.
 

Fred

Well-Known Member
May 31, 2010
296
5
365
Covington, LA
This the explanation I get from the seller: ..."however the initial brightness is not from gas, but rather from differennt reistances in the heaters that even out after they warm up. There is nothing to worry about."
 

DaveyF

Well-Known Member
Jul 31, 2010
6,129
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La Jolla, Calif USA
Fred. the best way to determine what is going on with the tube IMHO is to put it on a tube tester;)
Whenever I have had a tube flash in the past, it usually was followed by a problem and a failed tube. More likely in a power tube than a small signal tube, however.
Like mep said said, euro tubes are known to flash occasionally, however, sometimes that does signal a problem with the tube itself and not something that is normal. You might want to consider taking the tube and maybe the amp to a qualified tech and having them check it out. This is what I did when i had a GE 6550 give up the ghost on my ARC amp...I now have a lot more peace of mind:cool:
 

jadis

Well-Known Member
Apr 28, 2010
12,361
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Manila, Philippines
In my own experience, I have never seen a Telefunken tube flash upon start up. Mullard tubes do, almost in all that I've used, and the light is orangy yellow, not white. If you have a pair of Teles and only one flashes, then something is quite strange, specially when you affirmed there is a <> at the bottom. But I agree, some Teles with <> are fakes, as I have seem them. What gave them away was that the letters and numbers were like printed yesterday, as in fresh paint job. NOS tubes that were made 40 or 50 years ago will have letterings whose paint are faded and easy to rub off but there are a few exceptions. Teles have a lettering style with batch numbers starting with U then some numbers printed on the tube running sideways. If your dealer is reputable, then there should be no fear, but still this is the first time I hear that a Tele will flash on start up.
 

mep

Member Sponsor & WBF Founding Member
Apr 20, 2010
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I repeat-there is nothing wrong. Do not worry about testing your tubes and certainly don't take your amp to a tech. They only flash for a second upon turn on. There is no need to look for a problem where none exists. If you must worry, like I said before, please remove all European tubes that flash and send them to Uncle Mark's home for the wayward tube flashers.
 

Fred

Well-Known Member
May 31, 2010
296
5
365
Covington, LA
I repeat-there is nothing wrong. Do not worry about testing your tubes and certainly don't take your amp to a tech. They only flash for a second upon turn on. There is no need to look for a problem where none exists. If you must worry, like I said before, please remove all European tubes that flash and send them to Uncle Mark's home for the wayward tube flashers.

Tubes Gone Wild! Someone should make a video...:)
 

Fred

Well-Known Member
May 31, 2010
296
5
365
Covington, LA
Update: 8 months in and my flasher is still flashing its little heart out. God Bless It! :)
 

mep

Member Sponsor & WBF Founding Member
Apr 20, 2010
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I told you not to worry Fred.
 

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