Did I loose vacuum ?

[Bub]

Hi Gentlemen,

I have a quad of NOS 6550s but on one tube there seems to be no flash on the side getter but the top getter appears to be flashed. I've read when a tube looses it's vacuum it goes clear but the side of the tube is perfectly clear. I would like to sell these but I want to represent them correctly. It works and sound great. Would you call this a bum tube ?

Thanks

Rob

[Ed_Chambley]

If it works, it is good.  That is a simple statement.  Question is usually it will look very blue compared to the other if oxygen is present.  Do you have a tester?

Usually people want to see Gm numbers which does not tell the whole story, but it does let you know if the tube is working at the testers current.  Put them in an amp as a pair.  I have never seen a bad tube clear and it is strange looking without getter flash.

I have a maximatcher and would be happy to test it for you if you would like.  Just PM me and I will give you my address to ship it to me and I will test it for you.  If you want to send both, I will test them both.  If you put them in a circuit and bias them you will know for sure.  That is really the best way to tell if they are matched.

[Bub]

Thanks Ed,

When I bought them they were TV7 tested and matched very close but I can't find the info.
I do have a B&K 650 emissions tester but I,m still looking for the settings. I don't know if it will test a 6550, not listed in the book and I know its not a very good tester. I have two amps I've put them in and they work perfectly and bias up no problem, no blue glow. One amp is 400v on the plates and the other is 550v. I'm wondering if it was never flashed when built.

Rob

[PRR]

http://www.el34world.com/Forum/index.php?topic=9120.0

[Bub]

These are three, two side and one top getter. I had totally forgoten about that post but I still don't understand why it's clear.

[PRR]

Tung-Sol has built 6550's using one (top),  two (top + side) or three (top + sides) getters.

[Bub]

Ok, I know I'm not the sharpest tack in the box but is that not the side getter in the picture ? I thought these were flashed at the factory. Sorry, I don't understand FYL answer.

Thanks

Rob

[HotBluePlates]

I've read when a tube looses it's vacuum it goes clear but the side of the tube is perfectly clear.

Whoever wrote that was wrong. When air leaks into a tube, the silver flash turns chalky white.

Can't say why the side flash didn't happen in your one tube, though it appears there are getters on the side. Maybe when Tung-Sol made it the side getter wasn't loaded with the metal that gets flashed onto the glass.

Regardless of the reason, the shiny silver top getter tells you this tube is doing fine. I think you are worrying over nothing.

Sorry, I don't understand FYL answer.

It means Tung-Sol had at least 3 variants of these tubes, and may have had 1, 2 or 3 getter flashes, depending on the variant.

I would like to sell these but I want to represent them correctly.

Ebay buyers may have partial or poor information, and it's a losing proposition to try to educate them all. If it were mine, I'd sell it as a good tube. I might also include info on measured transconductance and idle current at a given plate and screen voltage.

[Bub]

Thanks Ed, PRR, and HBP,

I found the test numbers written in pencle on the inside of the boxes.
12750, 13250, 13250, and 11750 so I'll do some research to find out if these are good or not.

Thanks for all the help
I'm feelin warm and fuzzy now

Rob

[plexi50]

Air in tube

[HotBluePlates]

I found the test numbers written in pencle on the inside of the boxes.
12750, 13250, 13250, and 11750 so I'll do some research to find out if these are good or not.

No telling what those numbers might be. They're too high to be measured transconductance, wrong order-of-magnitude to be idle current. I doubt they provide any useful info without knowing what the previous owner meant when they wrote those.

[Bub]

As you said HBP, I'm not getting anywhere with those numbers. Time to keep it simple.

 Now I see what air in a tube looks like. That thing looks like it's ready to pop!

Thanks

Rob

[Jack1962]

Your numbers are lot numbers , if the tubes work they are good , the glass isn't milky there is no leak brother.

[jojokeo]

Plexi - that tube makes me want an ice cream (it's after dinner time here). The wife just got some Klondike bars too which is perfect after eating BBQ buffalo chicken breasts.

[plexi50]

Plexi - that tube makes me want an ice cream (it's after dinner time here). The wife just got some Klondike bars too which is perfect after eating BBQ buffalo chicken breasts.

It's weird man. It's like a real live cumulus cloud or a hurricane in a bottle. Whipped cream too! Talk about 3D. Im wondering if this aint the fourth dimension?
I dont want to mess with it. I might wind up in Night Gallery or the Twilight Zone

[Davidg]

Im a bit surprised that this is an unusual problem. I have 2 out of 4 RCA blackplate 6L6GC's all with matching dates that are like this with all flashing gone except for one small rusty looking spot of the side flashing left, the other two are missing no flashing but all 4 work though I havent took any measurements or tested them.They came out of a silverface Fender PA 100.I also bought a 66 blackface Bassman AB165 last weekend (along with Fender cab with 2-15" JBL D-140 and a 73 Mustang bass all from original owner) and one of the RCA's in it had the same problem-almost no flashing was visible and all top was gone the other tube was like new and the tube with no flashing was the good one, new looking one was a dud.I assumed in both amps there had been a bad mismatch and one had been drawing way more current than the other

[tubeswell]

I've read when a tube looses it's vacuum it goes clear but the side of the tube is perfectly clear.

No. When I tube loses its vacuum the getter turns powdery white.

On the other hand, when the getter stops being effective in an old and worn out (but still barely functioning tube), it sort of fades away a bit, especially around the edges of the getter material, but that is different. In your picture there is still plenty of getter material within the tube.