Valve amp issue (pls see picture)

[Zoidburg]

Hi everyone,

can anyone offer any advice on why my Audioromy amp may have started to
burn far brighter in one of the valves than the others? Is it something I should be worried about? And what can I do to sort it out?

The link below may help, its to a photo on my flickr account showing the amp and one of the big fu / gu29 valves that's got the issue.

http://www.flickr.com/photos/53210713@N06/8561485155/in/photostream

Any comments / thoughts / diagnosis would be a real help.

Thanks in advance.

cheers,

Ben

[ppat2]

I am not any sort of tube expert, but I recently purchased a tube amp, the Air Tight ATM-1.

It was working fine for a couple of weeks, but I noticed that one of the tubes was quite brighter than the others and this lasted for a few days. Not the extent yours is, but the same effect.

A few days later, that tube failed in a big flash with several other tubes going at the same time, and quite the noise from the amp and loudly humming speakers. Gave me quite a start.

The amp was "dead" at that point, meaning it would not power on, not even after replacing all tubes with new.

In for repair it was discovered that the problem was a single blown capacitor, and the repair cost was less than $100. Tubes were biased while in the shop and good as new.

Maybe a trip into a shop for a check up might be a good idea? Might prevent a larger problem.

Or, it could possibly be also a tube failing? Maybe some experts could opine on whether it is normal for a failing tube to burn brighter than the others.

[Lodgesound]

Ben;

DON'T whatever you do run it anymore - something is pulling way too much current through that valve.

As has been said I would suspect a capacitor but it could be any number of things including shorted turns in the output transformer.

Get it checked out as soon as you can. I would recommend replacing all output valves or at the very least this one as internal damage may have been caused which could lead to a short internally in the future.

Looking at the picture it looks like it may be an internal heater-cathode short in the tube itself which would cause this overly bright burning - either way you must get it checked out as further damage could be very easily caused through running it now.

[Zoidburg]

Thanks guys,

not the news i was hoping for but at least i may have caught it before any damage done.

Anyone know where i could get it looked at / repaired in the north west area, preferably near Liverpool/ Chester / Manchester?

cheers

[Firebottle]

Ben it looks like one half of the left hand output valve is pulling way too much current. It look like the anode plate is glowing red hot.

The anode plates should not glow at all, it shows the valve is way over it's dissipation rating which will shorten the valve life considerably if left as is.

The probable cause is a short on the capacitor feeding the signal to that half of the valve, or there is a fault in the biasing circuit. It sounds like you don't have the expertise to look at it yourself as you are asking for a local repairer.
If you know anyone with some electrical knowledge they should at least be able to test for a shorted capacitor. Another possible area of expertise is a radio amateur (of advancing years) as they may well have experience of valve use.

Good luck with finding a fix,

Cheers, alan

[DSJR]

Ask our Anthony_TD (Tube Distinctions), or even Glenn Croft, who will tackle any valve product if he's not too busy.

Graham Tricker (GT Audio - Tron fame) used to do great repairs and restorations as well, but I understand he's expensive these days.

As said above, PLEASE don't use the amp until it's sorted out. Get a cheapo Mini-T style as a spare for such an emergency...

[Ali Tait]

Nick (Lurcher) may fix it if he has the time. Be worth a PM.

[Zoidburg]

Thanks dudes for the advice. Iv turned the amp off and wont touch it again until its been looked at.

Gonna investigate a few options for repairs so will report back shortly.

Cheers

Ben