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[leadfootdriver]

I just had a KT88 redplate on me. They're not that old at all and should have years of life left. I'm bummed. The pair have about 550vdc on the Plates and are rated for 100 watts.

There was a thread a while back on another forum where the Merlin debunked Cathode Striping so there's nothing to worry about by just turning the Power and Standby on and playing. This is what I've been doing lately here in the house but playing at very low volumes. HOWEVER, I wonder if I could have prevented the failure by letting the tubes warm up a bit and allow them to stabilize with heat before hitting the Standby..

What are your thoughts??

[nickb]

First you need to rule out other component failures - bad coupling cap, socket and instability issues spring to mind.

[leadfootdriver]

It's the tube. I can switch positions and it's still RP's.. I have another set in there now and they're fine..

[loudthud]

I had some 6550s that I got on ebay. One had no plate current, it all went to the screen. You could see in the base of the tube where the weld to pin 3 was broken.

[galaxiex]

Bad/defective tube.

[leadfootdriver]

Thanks for the reply's.. How does everyone like the new Genalex Gold Lion KT88's? They're from New Sensor, but are somehow way more expensive compared to others. The reviews are good though..

[Leo_Gnardo]

Thanks for the reply's.. How does everyone like the new Genalex Gold Lion KT88's? They're from New Sensor, but are somehow way more expensive compared to others. The reviews are good though..

So far I've only seen one. It was a failed tube, looked brand new. Not to say they're all like that. I was expecting the innards might look different, but no, from the outside it looks just like EH/Sovtek standard. No secret that New Sensor charges a premium for their tubes with vintage brand names they printed on the glass. If the Gold Lions really are superior, so far it's only through reviews. My muso friends refuse to pay the markup for the fancy brand name. OTOH a recognized expert, Jim McShane, a respected tube dealer & hi fi refurb wizard in Chicago, thinks highly of the Gold Lions last I checked. And he's no BS artist. If you're serious, and willing to pony up the dosh, get a hold of Jim, let him know what amp you'll be using them in, what its B+ and screen voltages are, and he'll burn in & test a matched set for you. He has provided sets for vintage SVT's, and I'm sure he would do the same for any others. Dig deep & I hope you're pleasantly surprised.

[leadfootdriver]

Thank you. He has quite the selection of tubes. I suppose I could try a pair.

[Gaz]

Pass on the "Genelex." Most reliable KT88's I've found are JJ's from Ruby, and they have a 6 month warranty. I would say it's the 550vdc on the screens that killed your tube, but you said you've only been play at low volume, so not much screen current. But I concur, don't blame the standby - it's a coincidence.

[alexradium]

yeah,550v on screens you are asking for trouble no matter the tube you put in.
What amp is it?

[Randall]

+1 on Jim McShane. He went well out of his way to tutor me via email, and answered all my questions when I was a noob and trying to get my head around tube theory. Good Guy.

I had a Marshall Silver Jubilee in a couple years ago that was eating KT66s due to the exact replacement spec PT cranking out higher B+ from today's higher line voltages. It came in with an arcing Gold Lion. My solution was to make him a bucking transformer to lower the primary side, and thus the B+, and put in a quad of Ruby KT66C from Valve Queen, tested, burned in and matched at their highest voltage setting, with their 6 month warranty. Never saw that amp again.