[highstream]

I picked up a supposedly good 1948 Philco 5U4G earlier this month to run in a Supratek Chardonnay preamp's PSU. After about 7-10 days of working and sounding great, it didn't start up (no heater light, no sound). Reseating got it going, but it happened again the next time, at which point pushing down on the tube got it going. Since then it's started up every time except maybe two or three times, and one time the other day I noticed it took it's time to start.  Until today. Today it didn't start at all, no matter what. Contact cleaner had no effect. At the same time, other rectifiers run fine, which seems to rule out a socket issue (the preamp is 10 months old). Putting the tube in a Lampi dac, I noticed it lighted up and then dimmed, continuing that cycle indefinitely (didn't check for sound). So I contacted the seller, who said maybe the pins need lengthening. I'm ignorant of their attachment inside and thought from the seller's comment maybe they could be unscrewed a little to lengthen them. However,  it looks like all I did with a pair of pliers was mark up the pins' surfaces a bit. In any case, after trying that the tube started right up. Since then, however, it doesn't start unless I move the base back and forth a bit. The seller now says changing the angle of the pins should solve the problem. Since they looked good to start, much like the other rectis I have, so that explanation doesn't make obvious sense to me.

So my question to experienced hands is, What is to be made of this? Is there anything I can do here or is it a sign of something inside not being right and thus need to go back? Photos attached (there is a guide pin). Thanks,

[FullRangeMan]

Reseating got it going,
What do you mean say by reseting ?

This tube are unused since 1948?

Do you have activated the getter before use?
The getter goes inactive after 6 months of no use.

[thorman]

 Hello : It would seems to me that those pins are quite Thick and Rigid and not easy to change angle or adjust like a Preamp input tube. Also why would one bend pins on a tube only to create some damage for the next tube down the road. Your best bet is to ask for your money back and move on to another place to buy this Rectifier tube. It certainly sounds like a bad connection and who knows it could just be a fault inside the tube where the Pins connect and it is not visible. If you can't get your money back, buy another tube and chalk it up to a mistake buying a Used Vacuum tube from a " Non " Tube Dealer . To be honest I would not screw around with this tube any longer and you could be sorry and have to spend more money ( for repairs ) of you do. This tube could very well have worked perfectly from the person that sold it to you. These things sometimes do happen and when they do move on ....Good luck

[highstream]

Reseating got it going,
What do you mean say by reseting ?

This tube are unused since 1948?

Do you have activated the getter before use?
The getter goes inactive after 6 months of no use.

I wrote reseating, not reseting. If getters go inactive after 6 months of non use, then how does that jibe with the tens of thousands, if not a lot more people, using decades old NOS tubes, let alone slightly used ones, myself included?

[DaveC113]

I can't tell but it kinda looks like the getter has disappeared? If so it lost vacuum, not good.

Also clean contacts, it's good to be sure the socket isn't gunked up.

[highstream]

I can't tell but it kinda looks like the getter has disappeared? If so it lost vacuum, not good.

Also clean contacts, it's good to be sure the socket isn't gunked up.

The pins appear clean, and I did use contact cleaner. I'll admit not knowing all the parts, but does this photo help with what you were looking for?

[DaveC113]

Pins look good, make sure to clean the socket too.

Looks like the getter is at the bottom in that pic, and it looks like it's still there.

[highstream]

Based on the information provided here and on another place I asked, the seller agreed to a refund without needing to send back the tube.

Since everything else seems to be in order, it's been suggested that possibly there is oxidation of some solder joints. In particular, with a 5U4 someone pointed to pins 2 & 8. How does one re-solder pins? I have a replacement on the way, but maybe I can find a local who would be willing to help salvage this one.

[FullRangeMan]

I wrote reseating, not reseting. If getters go inactive after 6 months of non use, then how does that jibe with the tens of thousands, if not a lot more people, using decades old NOS tubes, let alone slightly used ones, myself included?

OK. Its understandable that the rectifying socket show looseness before the others, this is the valve that heats up more.

Iam not sure how the current production tubes getters are operating today, certainly the manufacturers will not inform us on this point to keep us without this critical information that would give us a tool to judiciously evaluate its tubes.

Six months of inactivity is what is estimated by books of the time about NOS tubes with barium dust getter to it starting sleeping according the amount of getter dust present inside the bulb, not sure about donut zirconium getter, of course a tube with more getter dust inside than other will have more capacity to clean the gases and vaporized metals inside.

I can not do this market research to find out how these NOS and new production valves in use around the world are performing today, but how the getter usually works inside the valve are referred by Tomer/Getting the Most Out of Vacuum Tubes page 23, easily available in PDF for free.