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Getterless Sylvania 6L6GC?

AbaddonD

Member
2015-08-20 1:49 pm
So I was looking at some tubes a few days ago and I saw the one and only 6L6GC on sale in Iran. It's a second hand Sylvania with the original box.

Now, everything seems fine to me except the getter. It seems to have the getter disc/ring, but it doesn't appear to be flashed. I'm not sure if this tube wasn't flashed when manufactured or there's something horribly wrong with it.

It's cheap though, around $9. The seller states in the description that "It's worth over $40 on foreign websites".

Do you think it has the barium azide on the ring that I can flash with my induction heater or it just has nothing?

I have attached the pictures of the tube.

Thanks!

20200310_030350.jpg
20200310_030329.jpg
 
I would avoid this tube.

15 years or so I was at a surplus auction at a NASA maintenance facility in Florida. I bought a new, never opened bulk pack box of 100 Sylvania 6V6GTA's.

I was quite surprised to find no, white, or cloudy getters on about 20 of the 100 tubes. They were indeed bad tubes. In fact most all of the tubes had issues, or would develop them in the 15 years that I have had these tubes. I can't trust them in anything since a good one can turn bad overnight. There had to be some kind of contamination issue with them.

Here is a picture of 7 tubes ranging from no visible getter at all, to cloudy, to some shiny spot left. All will glow a gassy blue glow, draw excessive current and some will arc over internally. I stuck some of them in a working amp and let them play to see if some use would make them better or worse. All got worse, but the experiment ended when one arced over causing the cathode bypass cap to explode.
 

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AbaddonD

Member
2015-08-20 1:49 pm
I would avoid this tube.

15 years or so I was at a surplus auction at a NASA maintenance facility in Florida. I bought a new, never opened bulk pack box of 100 Sylvania 6V6GTA's.

I was quite surprised to find no, white, or cloudy getters on about 20 of the 100 tubes. They were indeed bad tubes. In fact most all of the tubes had issues, or would develop them in the 15 years that I have had these tubes. I can't trust them in anything since a good one can turn bad overnight. There had to be some kind of contamination issue with them.

Here is a picture of 7 tubes ranging from no visible getter at all, to cloudy, to some shiny spot left. All will glow a gassy blue glow, draw excessive current and some will arc over internally. I stuck some of them in a working amp and let them play to see if some use would make them better or worse. All got worse, but the experiment ended when one arced over causing the cathode bypass cap to explode.

Ouch!

It's a pretty odd manufacturing defect though.
 
Yeah. The seller had stated that the filaments were OK, but that's just a fraction of the story. And I guess he checked it with a multimeter or something because if there are gasses inside the tube, the heater will consume a lot more power and the heater probably won't glow as bright as it used to.

I think unless there is no vacuum the heater will still be OK. The seller should/will have noticed the white on the top and should have binned them. They are not fit for purpose and I would ask for money back.
 
Sylvania had some quality control issues in final years of vacuum tube manufacturing. I got a large lot of NIB 35LR6's where the top taps on the plate structure were not given the bend or twist needed to hold the top mica to the plate. I plugged 4 of them into a modified version of Pete's big red board, but some serious fireworks and burnt parts occurred on power up. One of the tubes had a short between G1 and G2.

This prompted a visual inspection of all 44 tubes. Some were fine, but should not be banged around or operated upside down.....others failed the obvious visual inspection test.

The sick 6V6GTA's were older, not from the last days. There must be some kind of contamination or slow air leak associated with these tubes, and possibly the lot that that 6L6GC came from.

I had to pack up all my belongings and move 1200 miles about 6 years ago. I sold, gave away, or trashed everything that I did not want to move. I went through the remaining 6V6GTA's in that box and tested them all for THD in an SSE amp. Everything that didn't come close to some old metal 6V6's went into the trash. The rest were boxed up and moved. There was only about 20 of the original 100 tubes remaining. I haven't found that box, but when I do it will be interesting to see how many more have died.
 

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AbaddonD

Member
2015-08-20 1:49 pm
I think unless there is no vacuum the heater will still be OK. The seller should/will have noticed the white on the top and should have binned them. They are not fit for purpose and I would ask for money back.

It will glow, but at much higher currents. When my 2C39A cracked after it hit carpet, it would draw like 4A at 5V instead of 1.1A and it wouldn't even glow! So yeah...

Oh I haven't actually bought the tube. I was just browsing.

Thanks!
 
Hopefully they'll stay this way

Since they all appear to look the same, they probably will.

My box of 100 6V6GTA's that I discussed in post #3 had several white top, milky top, and totally clear tops when I first opened the sealed Sylvania bulk pack box. I tossed the obviously bad tubes at that point, probably 30 to 40 years ago resealed the box and put it on the shelf in my closet. Some time later, around 2000, I decided to build some SE guitar amps, and found some more bad tubes. They were tossed. This process repeated several times over the years. One or more of those tubes had failed rather quickly in the guitar amps I had made, and were replaced with Russian tubes, which lived long lives.

When I was preparing to move 1200 miles I hooked up a SSE test board and prepared to test the rest of the tubes in a working amp. I ran each of these tubes through the amp testing them for THD at 2 watts in triode mode. All defective, unstable or high THD tubes were tossed. There were 34 good tubes out of the original 100 left. I boxed them up and put the box in the tote to be moved. That was about 10 years ago.

I just opened that box for the first time in 10 years. There are two obvious white top tubes, two more that are nearly clear, and about 10 that have obvious getter degradation.

It is obvious that there is some manufacturing defect with these tubes, so NONE of them can be trusted. Next time I have an SSE board on the bench, I'm going to "test" them a bit beyond the specs...….my power supply goes to 650 volts!
 

AbaddonD

Member
2015-08-20 1:49 pm
Since they all appear to look the same, they probably will.

My box of 100 6V6GTA's that I discussed in post #3 had several white top, milky top, and totally clear tops when I first opened the sealed Sylvania bulk pack box. I tossed the obviously bad tubes at that point, probably 30 to 40 years ago resealed the box and put it on the shelf in my closet. Some time later, around 2000, I decided to build some SE guitar amps, and found some more bad tubes. They were tossed. This process repeated several times over the years. One or more of those tubes had failed rather quickly in the guitar amps I had made, and were replaced with Russian tubes, which lived long lives.

When I was preparing to move 1200 miles I hooked up a SSE test board and prepared to test the rest of the tubes in a working amp. I ran each of these tubes through the amp testing them for THD at 2 watts in triode mode. All defective, unstable or high THD tubes were tossed. There were 34 good tubes out of the original 100 left. I boxed them up and put the box in the tote to be moved. That was about 10 years ago.

I just opened that box for the first time in 10 years. There are two obvious white top tubes, two more that are nearly clear, and about 10 that have obvious getter degradation.

It is obvious that there is some manufacturing defect with these tubes, so NONE of them can be trusted. Next time I have an SSE board on the bench, I'm going to "test" them a bit beyond the specs...….my power supply goes to 650 volts!
I broke the top of my PY88 yesterday and air got in. I learned a lot from that loss actually.

I learned that it takes time for the getter to react with the air and turn to the oxide form (white). (About 10 mins in this case)
I also learned that when the getter turns white, there's not much of it on the glass and the getter area might look like normal glass, especially in photos.
The getter's probably a few hundred nano meters thick or a micron thick at best.