All these old Eimac tubes are gassy because of their age but there is a way to revive them as long as all the filament sections are glowing and the filament isn't shorting against the grid... The way to do it is put the plate transformer on a variac and ground the grid... Power up the filament and let it get nice and warm. Slowly bring up the plate voltage from zero volts to where the plate starts pulling current. Slowly bring plate voltage up to where the plate is dissipating 100-150 watts, where the plate structure is actually glowing a dim red. When the plates start glowing, they will eat up the gas in the tube. There will only be a few hundred volts on the plate when it starts glowing red. Most people screw up these tubes because they have no idea what they're doing and start out placing 1000-2000 volts on the tube and the tube blows.
I am listening to what you have to say and agree from my own experience that it takes only a few hundred volts on the plate (with the grid tied to the plate) for high levels of plate current and a glowing hot anode in even the high mu triodes. It is the idea (or fact?) that the plate is the "getter" and absorbs the gasses in the envelope if operated at some high temperature. I can see this might be true and work if the only gas in the envelope is the "out-gassing" of the internal material in the tube envelope but if the seals are leaking, this is not going to work as the gas volume is too large. Our experiences of "degassing" tubes are anecdotal and lack the rigors of scientific investigation. From Eimac documentation, they state it is necessary to heat the anode "getter" structure to just below the limit of physical destruction of the tube in a lab environment to achieve this "getter" action by the anode. There seems to be some belief/information that tubes that are run with orange hot anodes in commercial installations last longer than ones run below the orange hot anode level. In the case of the tubes I posted in this video, the filament structure was damaged due to age or shipment or, whatever. They were, in my case, damaged where the filament structure had fallen downward and partially out of the grid structure. Obviously, anything beyond our repair. I suspect much damage happens in shipment of these old and fragile tubes of yesteryear.
@@ElPasoTubeAmps I buy those cheap Mtester T4 two at a time because crap packing one screen always breaks without fail. Got my order with a broken one...again. Seller is sending 2 new ones just in case the other fails soon.
i've got 2 good ones, stored away , was used at 3kv in a RF metal smelter, was given it many moons ago, tested it at packed it away, i been wanting to build something with it but never got around using them.
My wife of 45 years has been diagnosed with pancreas cancer so life has not been so kind lately. We are doing all we can. I try to keep a little bit of normalcy in life.
@@jimcatanzaro7808 Hi Jim, Thank you for your response. We are doing OK. There seems to be no cure other than a miracle but at least today the symptoms can be treated and life has the opportunity to remain normal, and pain free, as far as reasonable daily activities goes. It is a real energy robber of energy for the affected one. We learn to live with what we have and be very thankful for all the good we have had throughout our life.
I did consider that and is the reason I used the small wire clip leads to provide some bit of shock-absorber resistance in the line to limit inrush current. It was just too late for three of the tubes. And, who knows, they could have been broken in shipping being jarred around by the postal service. I don't know for sure but these tubes are probably from the 1950's,
That’s disappointing. I see so many tubes, especially large transmitting tubes for sale and I have to believe a lot of them are no good. I’ll bet they keep getting bought and sold. You see 3-500’s for $300 or so. That’s a lot of money to lose if it turns out no good.
This Ebay seller was totally honest. He refunded all my money including postage so effectively he sent me one for free and paid the postage. I totally agree that there are way too many supposed "NOS" tubes for sale on Ebay. I can see the brown shellac looking substance inside the glass envelope in many of them and some have the black ring burned on the shield below the plate. Obvious they are pretty fried. Got to make sure we buy from honest sellers. A few years back a similar thing happened with a pair of beautiful 813 that had no filament when arrived. Again, an honest seller refunded my money. I bought a pair of perfect looking 4-400A a year or so ago and one was good and the other dead. I made a video of it trying to "degass" it. It did not work. The seller gave me back all my money but wanted the good one back so he had to send me packaging and postage - but it worked out. And lastly - I got really screwed a few years back on a 3-400Z that I should have known better for and that seller was a real thug and I waited too long to test it and even Ebay abandoned me. Got to be careful.
