Lets settle the b+ on cold tubes issue!

[Magz]

I like to use two ON switches for my tube gear, the first to turn on bias supplies and filaments, the second to apply B+. It's just how I do things, and it does help in initial debugging and troubleshooting, being able to selectively turn off portions of the units.

[TonyTecson]

Originally Posted by wkirkpa

Do your builds include any features that may indirectly serve a similar function, or perhaps render it moot?

Like using a tube rectifier vs. SS type, for example? Maybe a well regulated HV supply that is very much within the tubes' specs? Even, perhaps, something like using thermistors on a dual transformer (heater separate from HV) might serve much the same function.

Does your 5 year baby use "big" output tubes? I've seen it said that signal type tubes generally live a great deal longer than than the big bottle power types.

Sorry for my obviously focused interest. I'm ok with re-tubing, but at between $500 and $1000 using current production tubes, I'm really in no hurry to do so. (The new toy is a 5 channel, 10 tube KT90, Ming Da). I'll mod it eight ways to Sunday, if it will help. I just need the information to do so in an both an informed and integrated way.

BTW, the thing came with a standby switch. Love to be sure if, or how, to use it.

not that big, mine was a 6LU8 sweep tube using both ss and tube rectification in a hybrid mode...
but have done a marantz 9 clone using only SS rects, i used NTC resistors in the primary winding of the mains traffo...

not yet 5 years old but....uses ss rects...
[IMG][/IMG]

[wkirkpa]

Originally Posted by Magz

I like to use two ON switches for my tube gear, the first to turn on bias supplies and filaments, the second to apply B+. It's just how I do things, and it does help in initial debugging and troubleshooting, being able to selectively turn off portions of the units.

Does it seem to help any with tube life?

I'm seeing signal tubes rated for up to 10K operating hours, power tubes in the low/mid thousands. And, also, some power tubes lasting only into the hundreds of hours. I hear about tubes in old ATT switches lasting decades in operation, with only occasional and random failures.

The Audio Express article claims to have taken sets of tubes from hundreds (300ish) to thousands of hours (2500ish). His underlying circuit be what it may, his solution would seem to have circumvented something. Perhaps he could have rather engineered out a design fault, but the solution seems general enough to correct a host of possible faults that might happen to exist any any 'ol circuit.

Other simple, generalized, solutions (like grid+ heater) may also cover a host of other evils in any particular circuit. The key is does the solution suggest it may either insure, or exceed, expected operation? I don't think we'll ever see statistical certainty - but performance vs. published specs (which are also statistically determined) is a good second.

The way I figure it is, if someone is doing something that suggests they can get a "power" output tube *consistently* up to, and better yet beyond, its rated operational life... Then I'm game for trying.

Perhaps our standby switches, for those of us with them, should be wired for both heater - and grid. Is there any downside/risk to pre-powering the grid?

[TonyTecson]

when running over 1000 volts of B+, some sort of ramping up the supply surely comes in handy....i have such scheme on my 813 SE build...

for lower voltages say 400 volts, no need....

[wkirkpa]

Originally Posted by AJT

not that big, mine was a 6LU8 sweep tube using both ss and tube rectification in a hybrid mode...
but have done a marantz 9 clone using only SS rects, i used NTC resistors in the primary winding of the mains traffo...

not yet 5 years old but....uses ss rects...

Very nice. I was going to DIY the whole thing. Lurked around here for quite awhile. Eventually joined just to look at the pictures, actually.

My trouble was, by the time I priced the transformers, tubes, and chassis - I was already around the price of this unit from cattylink. What with sockets, connectors, I was well over. And I still had to do, well, something under the deck.

So, I laz'ed out. Bought the thing and saved an immense amount of time on procurement and purely physical construction issues. And it supposedly "works", if in only a relative way.

So, if I have to, I'll rip out the deck and do whatever. Still save time and money. On arrival the P2P wiring was, well, immaculate. Many above average and reusable components, nothing stellar tho.

As for the topology, I'm not sure yet. Still RE'ing the schematic. Could have got one from the factory, but they asked fully twice the price. Heck, if I needed a "warranty" I'd have bought two and had all the spare parts in the world, zero fuss, and a free compliment of tubes - and still saved about $20US over a factory unit. Alas, I decided to pay myself about $2000 to RE the circuit myself.

I haven't even played it yet. Maybe it's glorious. Maybe it doesn't need a complete refactoring, just some"fixing".

It does have a "Standby/Operate" switch, and I'd like to play it while I'm figuring things. But I don't want to prematurely kill a set of tubes. So for now, as my particular rubber hits the road, and like the OP, my inquiring mind wants a clue about how to "best" (most safely, tube life wise) use the thing.

[TonyTecson]

tubes have sockets because they are meant to be replaced and does not last a lifetime...
life of tubes will vary depending on how hot you run them and the class of service you put them in..

[wkirkpa]

Originally Posted by AJT

tubes have sockets because they are meant to be replaced and does not last a lifetime...
life of tubes will vary depending on how hot you run them and the class of service you put them in..

I'm totally comfortable with that. The trick seems to be in "the class of service you put them in."

I read of similar tubes living hundreds of hours, I read of them living into the low thousands, and the high thousands too. It seems, sometimes, a seemingly small detail can have an amplified effect (yes, pun intended). Infinite would be just fine with me, but double might do nicely.

I've seen commercial claims of numbers like 7000 hours for tubes rated around 2000. Can't recall where tho, been scanning just too much stuff lately. Maybe Its proprietary "magic", just wishful thinking, or maybe just a bit ethically challenged. Still, an enticing pursuit.

If it's real, then we're always allowed to figure a proprietary bit out for ourselves.

For many, differences like that are very meaningful. A good NOS tube ain't cheap. A good set of current production tubes ain't always cheap either. But, maybe, its all just a Grail.

Anyway, for now, I think I have plan. Good, or bad, I guess.

[DF96]

We keep telling you that you don't need a plan, and a poor plan might be worse than no plan.

For long valve life, run it continuously but well within its voltage, current and power limits. If this is not possible, then use a single mains on/off switch - unless it uses high power valves in which case use some automatic sequencing. Do not use manual sequencing, as users (including us) are not reliable.

[luckythedog]

Originally Posted by DF96

We keep telling you that you don't need a plan, and a poor plan might be worse than no plan.

For long valve life, run it continuously but well within its voltage, current and power limits. If this is not possible, then use a single mains on/off switch - unless it uses high power valves in which case use some automatic sequencing. Do not use manual sequencing, as users (including us) are not reliable.

Yes, that will do it. And don't do anything that slows down cathode warm-up ramp time, or intentionally cools the cathode from design spec ratings as to heater arrangement.

[TonyTecson]

I've seen commercial claims of numbers like 7000 hours for tubes rated around 2000. Can't recall where tho, been scanning just too much stuff lately. Maybe Its proprietary "magic", just wishful thinking, or maybe just a bit ethically challenged. Still, an enticing pursuit.

i never really paid attention to this, why? a tube can get broken in minutes if you drop them on the floor from a height....