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Tubelab_com 9th June 2008 02:51 AM

Photos - the death of a Simple SE and 6V6's
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I was doing some testing of some tubes and transformers in a Simple SE board today. The results are posted here:

During that testing I remembered a box of 6V6's that I bought about 10 years ago. They were millitary bulk packed Sylvania 6V6GTA (not wafer based 6V6GTB as I incorrectly remembered earlier). The box of 100 tubes was still sealed when I got it. Upon opening I discovered that many of the tubes had lost their vacuum. I tossed them and saved the rest. Last year I needed some 6V6's so I reopened the box. More of the tubes had turned white. I tossed them. I reopened the box this evening, and found 7 more white tubes. What wood happen if I put these tubes in an amp? I set out to find out.

The poor Simple SE board that I am using has been through a lot. It has been used for all sorts of experiments including the 550 volt test. It was hacked up and made into a push pull amp:

Then I put it all back together again to test some power transformers, so it is up for some more torture. I am going to name this one Buster!

Here is the line - up. there is one "normal" looking tube in the bunch. Note the silvery getter on the top of the tube on the right. All the others shoe varying degrees of air inside. DON'T PUT ANYTHING LIKE THESE IN YOUR AMP. You are about to see why.

Tubelab_com 9th June 2008 02:57 AM

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I tested the amp with a few of the normal looking tubes and they work fine. I have a Hammond 272KX power transformer which runs the 6V6 right at the maximum specs.

I selected a tube with some silver left showing. The amp worked, but the distortion was high. It rose from 3% to about 7% after 10 minutes and then stayed at 7%.

Next a tube with almost no silver left. It powered up OK the distortion started at 3.5% and took off almost immediately. There is a blue glow inside the plate.

Tubelab_com 9th June 2008 02:59 AM

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After a few minutes the glow got brighter and started to grow in size. The distortion had risen to 16% with severe flat topping.

Tubelab_com 9th June 2008 03:03 AM

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After about 5 minutes the tube was glowing brightly, and the amp no longer had any output. The grid was drawing so much current that the driver had given up.

Al of a sudden it died. no glow, no current, just a dead tube. I have more!

Tubelab_com 9th June 2008 03:05 AM

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Fresh tube in the hot seat, power on. This one glows more on power up than the other one did after 10 minutes, and it is getting brighter by the second.

Tubelab_com 9th June 2008 03:08 AM

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This tube is showing a very localized red spot. Something has warped inside to cause all of the tubes current to flow in one small area. This area gets hot, real hot.

Tubelab_com 9th June 2008 03:11 AM

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This tube has only been oprating for about a minute. I can tell that it isn't going to last much longer.

Tubelab_com 9th June 2008 03:18 AM

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Bang, PFFFFFFT, then the smell of an exploded electrolytic capacitor fills the room. The amp had a 2 amp fuse in place of the usual 1 amp fuse, and it had blown. This photo shows the aftermath maybe 3 or 4 seconds after the fuse blew. The screen grid support rods were glowng red, and the cap was still spraying its guts into the air (the cloud to the upper right of the tube).

The cap is toast, but the amp does not work with good tubes in it. The autopsy will be tomorow. And maybe some more experiments.

vinylkid58 9th June 2008 03:40 AM

Sad to see so many duds, how many actually survived out of the box?

I hope this isn't a normal occurrence, since I just bought a vintage amp will 6v6's in it.

Cool pics though.


HollowState 9th June 2008 03:49 AM

Well George, I assume you're doing this for fun since you surely knew what would happen. Maybe put a video on You Tube of a meltdown. You need some gassy 845's! I have a friend in upstate NY that once made some firecrackers with sulfur, aluminum powder and potassium perchlorate in a cardboard rug tube. That left a huge crater in the ground. Then the cops showed up and confiscated his chemicals.

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