300B valve failing? .... :-/

[jandl100]

My new (well, used!) Viva Audio 300p valve amp uses 2x 300B valves per side in push pull configuration.

Just now, one channel started to sporadically drop down in level, and one of the 300B valves has developed quite a strong blue glow all round the inside of the glass enclosure.

Is this valve about to fail / failed already? :scratch: :rolleyes:

[AlexM]

Yup. Blue glowing of the glass can be normal with some valves, but if the blue or purple-ish/violet glow is on the inside the plate structure, it is ionized gas and can cause serious damage to the amp if it experiences runaway.

I suggest you stop using it and replace either one or both (probably both).

Cheers,
A.

[RobsterD]

Hi Jerry,
why I don't like them,had 3 fail on me

[jandl100]

Oh poo. :(

Thanks Alex.

[jandl100]

Hi Jerry,
why I don't like them,had 3 fail on me

Oh god!!! :doh:

[Ali Tait]

Sounds like it may have gone gassy, i.e. let some air in. Bummer.

[jandl100]

:(

I bought the amp from Nick at the Emporium last week, I've only had it 4 days!! - I'll give him a call tomorrow.

[Ali Tait]

Is the getter all used up?

[jandl100]

Is the getter all used up?

Pardon? :scratch:

When it's not powered up, it looks pretty much the same as one of the 300B's that still seems OK ....

[NRG]

Whoa! A typical Blue glow is nothing to worry about, it depends on what it looks like, a picture would help.

http://www.rru.com/~meo/Guitar/Tubes/blue_glow.html

[jandl100]

Whoa! A typical Blue glow is nothing to worry about, it depends on what it looks like, a picture would help.

http://www.rru.com/~meo/Guitar/Tubes/blue_glow.html

Hmm.

Well, one has quite a strong blue glow, the other 3 do not.

Quite difficult to get a pic, but this will give you an idea ....

http://i262.photobucket.com/albums/ii114/jandl100/DSCF8434.jpg

[NRG]

Well its very difficult to make anything out from that but from what I can just about see it looks normal.


FLUORESCENCE

This type of glow is usually violet in color and most noticeable around the inside surface of the glass bulb. It is most pronounced on power tubes and is the product of electron bombardment of the glass taking place within the tube. It generally has no adverse affect upon receiver performance, and in fact, tubes displaying this phenomenon are particularily good with respect to gas content.

My KT88 amp glows like a good un, no issues at all with the power valves.

Why dont you swap the 300B pairs over from one channel to the other and see if the fault follows the valves, that will tell you if its the 300Bs or not.

[jandl100]

Hmm -- OK, thanks for that - perhaps I'll power her up again and have another listening session - I just hope it doesn't fail catastrophically! http://yoursmiles.org/tsmile/fear/t3615.gif (http://yoursmiles.org/t-fear.php) http://yoursmiles.org/ssmile/negative/s0936.gif (http://yoursmiles.org/s-negative.php)

... and see if I get any L/R balance anomalies again. :scratch:

[The Black Adder]

From the pic I take it that it's just the one valve doing that... I'd question it but my EL34's in my old Raddy looked the same except they all did it... They were a fully matched NOS quad.

Perfectly alright but it's just the one that would be up for investigation.

Might be the case that they are not a matched pair?

Nick should be able to sort you.

That is a lovely amp though, I was going to buy one at one point from Hughie at Emporium. Still intrigues me to see what it would sound like with the Tannoys now they are all finished.

[jandl100]

Yep, just the one - there's a slight tinge of blue from the one on the right - but it really is quite bright & spooky ! - and I am pretty sure it only started doing the dayglow thing yesterday ....

[The Black Adder]

Yep, just the one - there's a slight tinge of blue from the one on the right - but it really is quite bright & spooky ! - and I am pretty sure it only started doing the dayglow thing yesterday ....

As Neal said.. Have you swapped them over? see if the other one does the same?

[jandl100]

good thought, Joe (I hadn't noticed Neil's suggestion :doh:) ... lessee ... Ok, swapped the glowy one over to a different socket - the same valve still glows madly blue!

[The Black Adder]

In that case it sounds like a dodgy valve... Get a matched pair if you can.

Not sure if it's dangerous though but if it's sounding a bit rough then it's obviously a good move to replace them. I would also send the valves over to Anthony for a good check-a-roo!

With something like that I would always have a back-up set so if you get that pair checked and they come back ok then at least you know it's a pair to fall back on.

[NRG]

I meant does the channel imbalance follow the valves if swapped over :doh: :lol: not if the valve still glows blue!

[jandl100]

:lol:

I guess I'm getting distracted by all the snow - I'll power her up soon and see what happens. :)

[anthonyTD]

hi Jerry,
It does sound as though the valve has gone bad,ie; if it wasn't glowing like it is now before you had the power drop issues, then i would seriously suspect that valve.
Yes, as others have quite rightly said, the bluish glow just inside the glass is pretty normal on a lot of power valves, however, when you have the two issues you have just happened then it does point to valve failier, my advice would be to not use it anymore until you at least have it checked out.
Hope this helps. :)
Anthony,TD...

[jandl100]

Thanks Anthony.

As per others' suggestion - I have been using it this morning, for about 25 minutes so far.
The valve still glows, but sonically there have been no issues at all, it sounds great!

[daytona600]

looks like a duff 300b , checked my monoblocks 16 off them

[anthonyTD]

Thanks Anthony.

As per others' suggestion - I have been using it this morning, for about 25 minutes so far.
The valve still glows, but sonically there have been no issues at all, it sounds great!

Fingers crossed then! :)
However, i wouldn't advise swapping the two valves over [in this case] to see if the fault follows, mainly because if the channel "has" been damaged by the valve, then there is a good chance it could damage the other channel.
A...

[jandl100]

Whoops! -- ta for that, Anthony! :thumbsup:

[NRG]

Fingers crossed then! :)
However, i wouldn't advise swapping the two valves over [in this case] to see if the fault follows, mainly because if the channel "has" been damaged by the valve, then there is a good chance it could damage the other channel.
A...

I highly doubt it, its not a catastrophic failure.

[jandl100]

Valve is still fluorescing but seems to be working fine. -- it had several hours use last night and sounded fab.

I've sent Nick @Emporium a msg asking for his advice.

[anthonyTD]

I highly doubt it, its not a catastrophic failure.
And your very welcome to your opinion, however, i would still recommend being safe rather than sorry, especially as the owner [at this particular time] has no factual idea of what is going on.
A...

[Clive]

I haven't the whole thread on my phone but don't discount a leaky cathode capacitor or dc blocking cap if the amp is SE. The valve could be totally innocent.

Edit, I see it's a pp amp so as it's only one vavle under suspicion the dc blocker will be ok. Thhe cathode cap, if it has them, should be suspects.

[anthonyTD]

I would just like to add that a valve amp apparently showing an obvious fault [as this one seemingly was] seldom suddenly fixes itself, unless something odd as happened inside the valve, ie; temporary short,or bad connection etc,thus my opinion that it needs checking, its up to the owner to decide on that, either way, what ever the issue, something happened that affected the normal operation of the amp.
A...

[jandl100]

Quick update --

I've just spoken to Nick @Emporium, explained the symptoms.
He's happy that as the glow stayed with the tube when it was swapped over to t'other side, that the problem is with the tube not the amp.
So he is sending me a replacement 300B. :thumbsup:

[Marco]

...and if that one glows blue, when you plug it in, you can hit him over the head with it! :D

Marco.