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Old 20th April 2018, 02:10 PM   #21
anatech is offline anatech  Canada
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Colourful list Jon. It suffered from alignment issues. Under "advanced" there is a list function that might have worked better. Monochrome would be fine for this.

Many new tube brands do not like anything 450 VDC or higher. Sometimes they run into trouble below this.

-Chris
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Old 20th April 2018, 02:17 PM   #22
Tubelab_com is offline Tubelab_com  United States
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I wasn't expecting an amp chassis that had been removed from a combo unit and sold as - is without tubes on Ebay to work. I plugged it in and it didn't fry, there was AC coming from the power transformer and the pilot light was lit, so I looked in my big box of used tubes for a rectifier and found a 5U4 and plugged it in. Over 500 volts of B+ happened, so I went to the drawer marked 6L6 - 5881 and grabbed the crustiest looking tubes I could find, the 6L6WGB's. They lit up and no smoke happened. The B+ had dropped to about 465 volts indicating current flow, so I stuck a voltmeter probe on the grid and verified some negative voltage. There was a pop in the speaker when I probed the grid, so I stuffed the 12AX7 sockets and plugged in a guitar. Surprise, it works and doesn't sound bad.

I would have been happy to find a usable chassis and one or more good transformers. I needed the bench space for two amp designs I am working on, so it went on a shelf for a later date. I will have to measure its power output so I can decide what to do with it.

Quote:
When working on a Fender
I haven't worked on a tube Fender in nearly 20 years. Back then I used NOS, or Sovtek tubes. I fixed up a dead 100 watt Park (Marshall) amp a few years back and EH EL34's lived in it.
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Old 20th April 2018, 02:20 PM   #23
anatech is offline anatech  Canada
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Hi George,
Well, you won one! Congratulations!

I would not expect it to work either.

-Chris
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Old 20th April 2018, 02:41 PM   #24
rongon is offline rongon  United States
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Quote:
Originally Posted by anatech
7581A is a 35 watt device that retains the characteristic curves of the 6L6GC. 7581A sort of equals a KT66.
Right you are! Thanks, I learned something. I guess that monstrous 35W plate dissipation is one reason why Sylvania and Philips/ECG 7581s command such high prices.

https://frank.pocnet.net/sheets/135/7/7581A.pdf

Quote:
Originally Posted by Tubelab_com
The 6L6WGB is the internals of the 6L6GC with a rectangular box plate stuffed into a short bottle, originally for a military application. I have a dozen or so of these that came from military scrap, all well used. Some also carry 6L6WGB / 5881 designations.
And more nuggets of tube knowledge! Does the short bottle reduce the heat dissipation very much? I'd think it would, but in your experience?

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Old 20th April 2018, 05:11 PM   #25
Tubelab_com is offline Tubelab_com  United States
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I have not explored the upper limits of these tubes, so I really don't know. I have a whole drawer full of 6L6 types.

I have done most of my extreme testing on the older 6L6G's and GA's since I have a lot of them. I have seen 100 watts flow from a pair of tubes without glow....but I have seen two non fatal tube arcs trying to go beyond that. The tube lived to play on, the cathode resistor did not (1 ohm 1 watt 1% current sampling resistor).

I have a dozen or so of these 6L6WGB's and there are 3 different styles among them, there are probably more. The picture shows a RCA black plate 6L6GC next to a Sylvania 6L6WGB (also marked 5881 on the glass) and a Tung Sol 6L6WGB / 5881. The Sylvania has the largest plate, but the RCA has longer heat radiating fins allowed by the larger diameter bottle. The Sylvania has the familiar contoured plate seen in all older 6L6 types. I have seen the same plate used in Sylvania 6L6GC's. The Tung Sol has a rectangular box plate like that found in many modern Sovtek tubes. I'm guessing it's the wimpiest of the three.

Note how toasted the base of the Tung Sol tube is. This is one of the better ones, I put the real toasted Tung Sol tubes in the guitar amp. These things must get hot.
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Old 20th April 2018, 06:36 PM   #26
anatech is offline anatech  Canada
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That 5881 is just downright burnt. Too much heat buildup in the base, must have spent it's life upside down.

-Chris
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Old 20th April 2018, 11:29 PM   #27
Tubelab_com is offline Tubelab_com  United States
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These all came from a lot of over 100,000 tubes that I got over 10 years ago. The original owner ran a place that disassembled military surplus, scrapped the metals (his primary business) and shelved a lot of whatever he didn't sell. He had passed away maybe 5 to 10 years previously and his huge warehouse sat untouched for years. Vandals had broken the windows, and gotten inside and smashed up a lot of stuff over the years.

About 10 years ago the estate was settled and the property sold. The dozers came to flatten the warehouse and were in process of demolishing the place when someone decided that there were hazardous materials inside. My friend, another surplus dealer stepped in and offered a small price to buy the entire contents, which was accepted. He called me and said I could have ALL the tubes including all those hazardous mercury filled tubes for a couple of weekends time moving all the stuff into his warehouse.

There were over 100,000 tubes, all dumped loosely into boxes, wood crates, and even trash cans. In retrospect, it was a dumb decision since I had to move them all 200 miles to my place and pay warehouse rent while I sorted them all. That process took about 5 years, and I kept about 10,000 out of roughly 100,000. That number has been reduced to about 5,000.

The 5881 / 6L6WGB's came from this lot. I discovered stuff in there dating from the late 30's up to the early 60's. All military or aircraft related.

There was an unopened box from the Douglas Aircraft Company to an Air Force Base in Texas, dated Aug 1937. It had tubes inside.

Many boxes of bulk packed tubes, partially eaten by rats, and covered in bird poop. I stuffed all this into two 200 square foot rent-a-space warehouses. That 55 gallon cardboard drum in the lower right foreground is full of loose tubes. Most of them broken. Plenty of boxes like the Compaq monitor box, full of loose unsorted tubes. I set up sorting racks like these, first to presort by size, then to sort by number. About half the tubes were broken, or had pins to corroded and mangled to be used. I had fun blowing some of these up. When it was done there were about 10,000 useful tubes. Maybe 100 6L6 types, mostly older G's, GA's and GB's. Some I have since sold or given away. Here are some of of what's left. I have LOTS of 6AQ5's, some good, some not so good.

Bet you haven't seen a tube with a spare heater inside.....what's the odds of finding TWO of them. Both worked in a test circuit.
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Old 21st April 2018, 04:07 AM   #28
anatech is offline anatech  Canada
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That's pretty amazing George. What's even more amazing is that you stuck with it and sorted them all out! What a mammoth task for anyone, never mind expense. I bet you wouldn't do that again!

I think I see a bunch of old style radio tubes. Those are interesting. The 6AK5 looks like an interesting tube as well. So many tubes, so little time to explore. I can't imagine what you feel every time you walk into your tube storage area.

-Chris
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Old 21st April 2018, 11:38 AM   #29
Tubelab_com is offline Tubelab_com  United States
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Quote:
I bet you wouldn't do that again!
No way.....those are the dumm mistakes you only make once.

Quote:
I can't imagine what you feel every time you walk into your tube storage area.
I had to move everything I owned over 1200 miles when I retired. I knew that my career was on life support several years before it ended, so the "stuff" reduction plan was implemented. Things, including tubes, that I didn't expect to use in my lifetime were sold, given away, or trashed. There is one small bedroom in an abandoned house trailer full of tubes left, maybe 5,000.

I never did count them all, just counted one box that was full of everything, measured its dimensions, and weighed it. Guesstimated from that info.

Quote:
The 6AK5 looks like an interesting tube
Those two boxes of mostly little tubes were headed for the sorting trays when I took those pictures. Most turned out to be 6AL5 dual diodes. I probably kept about 25 and gave the rest away. There were several hundred 6AK5's, of which I kept a gallon bag full. There were some 6AS6's too. I kept some of those too. There were a few other tiny tubes which I kept.

Quote:
bunch of old style radio tubes.
I drove a Honda Element without seats full of tubes to all the local hamfests, plus the two big ones (12000 people) selling tubes. My prices declined as the shows drew towards the end, and often got as low as "free." I traded a trunk full of old radio tubes, mostly the metal ones, for an electric guitar at a hamfest. I still have the guitar.

I figured that I could buy the few radio tubes I would use in the rest of my life for less than it would cost me to move the lot of them. Ditto a lot of other stuff.
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Old 21st April 2018, 02:01 PM   #30
anatech is offline anatech  Canada
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Makes sense. I wish I was there at one of those Hamfests. You really didn't have many options, so you "done good". Now life for you is sane with regard to tubes and storage.

This is a great story for your young 'uns.

-Chris
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