Eh...what just happened?

[Diapason]

Well, having spoken to Bernard today and having been persuaded that attaching everything back up would be unlikely to be catastrophic, I turned the amps back on this evening and played some music. After a couple of minutes, I happened to notice that one of the big output valves was glowing all across one side, and it did NOT look healthy. Turned things off, but now I know what the problem tube is.

I didn't take a photo, but glowing normally they look like this:




In my case, that big grey plate you see in the middle was glowing ENTIRELY red-hot within a couple of minutes and looking very angry!!

On balance, this is a great result. Those output tubes aren't dear, and I'd been mulling over buying a new, properly matched set anyway having found a decent online source for them. Still means I'm ampless for the next few weeks, but not to worry.

[tony]

Thats great Simon. I wonder should you just swap it into another socket to confirm it is the tube? BTW I found this site very good cryoset.com
Prices for cryoed valves working out the same or slightly less per valve compared to others.

[Adrian]

Delighted to know you found the Droid you were looking for..........

[Diapason]

Thanks Tony, I might try that to be sure alright.

That site doesn't do the valves I need, and it's missing from many of the usual suspects. Plenty of options in Russia, Ukraine, etc., and I found some crowd I've bookmarked in work who offer them in matched pairs, so I'm gold.

And Adrian, that image is a thing of great, nerdy beauty!

[jaybee]

[Fran]

Its possible its the valve, but equally possible that its something else in there. Swapping 2 of the tubes around and seeing does the same tube red-plate in another socket would give you the answer.

BTW, thats called red-plating, basically the grey bit is the anode and its passing too much current. On some valves its normal to see a little bit of it (eg 300b), on others you never see it. Most valves are very hardy indeed and can withstand quite a bit of such treatment before giving up the ghost. Could be a resistor gone somewhere..... or if you're lucky just bias adjustment.


Example of a not too bad case (2nd form the left):



A worse case (apologies for the crap pic):



Fran

[Diapason]

Ah right, thank you Fran. Mine was probably somewhere between those 2 extremes, but closer to the latter. I really should read up about valves and how they work sometime because I'm sure it's not too difficult a concept to grasp, but at the moment I'm in the dark (especially now the valves are off, wocka wocka!)

So, I'll have a play around this evening before I go ordering a new set of output valves and I'll try to isolate the problem. I am at least convinced that is should be a reasonably straightforward fix once we figure out what's what.

[Ivor]

I'm now looking at the copious number of valve fuelled boxes in my room with deep suspicion. I think I might just listen to the kitchen radio for a few days....

[tony]

It would seem some soldering training is a prerequisit with valve amp ownership.That and an app for checking out resistors.

[Diapason]

Well, I'm probably a little bit to blame for my current troubles because there were signs that things weren't right and I chose to ignore them. I was also a little careless with switch-on and switch-off procedures and, let's face it, I'm big and ugly enough to know better. I went in with my eyes open, knowing that these occasional blips are potentially the price of valve ownership, but figuring that the sound and glow is worth the hassle. Every valve owner knows that financial outlay will be necessary from time to time, if only to replace the valves themselves, so I can't grumble too much.

Despite all that, I'm reading Devialet reviews...