Can I Test Old Vacuum Electron Tubes a simple way? - Page 6
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  1. #101
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    Quote Originally Posted by DaveKamp View Post
    Hee hee... I guess I was in the wrong place, at the wrong time, and some guy felt that I really, really needed to have it in my shop. Yeah, it was a good deal... I used that rascal to bring at least two dozen tranceivers back from the dead.

    Two things that gave me a chuckle here:
    Hollow-state... cool... but only if you never power 'em up...

    and I believe that it's difficult to maintain an 'unbiased' opinion when discussing vacuum tubes... this always leads to some sort of feedback. Someone's gonna howl. Let's face it- some of us have entirely too much on our plate, and there's lots of potential to violate someone else's envelope... It's really hard not to burst someone's bubble.
    Maybe so, but making them is another matter. Vacuum pumps suck!

    Bill

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  3. #102
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    Quote Originally Posted by 9100 View Post
    Maybe so, but making them is another matter. Vacuum pumps suck!

    Bill
    ...and air compressors blow.

    Tom

  4. #103
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    Sorry to revive the proverbial dead horse, but I was searching for a problem I'm having with on my big Ampeg SVT and it (of course) led me here again. JST... what was the MIL 6C4 tube you found worked in the SVTs? My 1971 Blue line has gone microphonic AGAIN. I'm buying new shock mounts and feet for it, but even the "NOS" which I think was a used tube in an old box) is ringing like a bell. A friend just recapped it and resoldered all the joints trying to get it quiet. Sounds like a train wreck when you tap that 6C4WA, even with both channel volumes all the way down. "NEW" one was worse than the one it has, actually fed back like a microphone held to a monitor when we fired it up.

  5. #104
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    We used those 6C4WA, but I think we did have some microphonic ones. It's crazy, because the thing is a cathode follower, it has no voltage gain, it's just an impedance matcher, and it should not cause that much trouble, but it can.

    Problem is that microphonics are not a MIL spec point for that tube, it's an RF tube, really. They likely used it in the original just because it was a single triode, but it would have been smarter to stick in a common 12AU7 and use just half.

    We found a source for decent ones. I do not remember where, unfortunately, may have been Richardson. You will probably have to try the silly things until you find a quiet one, and they are not all that common. I ought to make a plug-in solid-state replacement, but the market is tiny.

    I'll try to find the email for our SVT guy.... he is the one who resurrected the SVT for us, he may recall the deal, but it is pretty much going to come down to finding a quiet one.

    Yes, volume control does not affect it, it is in the preamp output, after all volume controls and after the two channels are mixed. Problem is that the power amp has a good bit of gain, so the noise is an issue.

    I met the designer of that beastie at the Namm show one year, I forget who he was working for, likely Fender. Anyhow, he was thoroughly "SVT'd out", so I just talked other stuff with him, stayed off the SVT entirely, even though we did have questions. . I'd like to know why the heck several things were done in that unit...... But I probably don't want to answer much about the stuff I did 10 or 20 years ago either, so I guess I understand.

  6. #105
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    There are military versions of the 6C4WA with thicker mica plates with 3 mica wafers and often heavier support rods. Often mil spec tubes had to meet certain vibration standards, but microphonics is one of those things that you just need to do a light tap test and listen for. I use a curve tester to map out the tube characteristics, some of the laboratory grade testers had oscilloscope inputs which could be used to look at tube microphonics. I just plug them in and use a pencil eraser and lightly tap the tube. There are also silicone rubber noise dampers and in some cases the sockets can be floating/isolated.

    You can look for the MIL-SPEC JG-6100, 6100, 6C4WA, typically branded GE. GE also had what they called a 5 star version which are had heavier mica spacers.
    JG-6100 6C4WA LOT OF 4 NOS GE TUBES, TV-7 D/U TESTED NOS #A-1 | eBay
    Platinum Matched Pair General Electric 6100 = CV4058 = 6C4WA = M8080 Premium Aud | eBay
    http://www.tubebooks.org/tubedata/GE_5star.pdf

  7. #106
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    " You will probably have to try the silly things until you find a quiet one, and they are not all that common. I ought to make a plug-in solid-state replacement, but the market is tiny."

    And therein lies the rub... Only way I can test them is to buy one, put it in the amp and tap it. I have three tube testers, but of course, there is no way to check microphonics with a tester. Guess I'll just have to buy and send back tubes until I find a working one.

    "You can look for the MIL-SPEC JG-6100, 6100, 6C4WA, typically branded GE. GE also had what they called a 5 star version which are had heavier mica spacers."

    Just bought that set of four. With both myself and a friend having older SVTs, we will undoubtedly go through them. Does suck to have to buy with no way to know if they are microphonic, though. At least they are cheap.

  8. #107
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    [QUOTE=The real Leigh;2599752]That's why I recommended the AntiqueRadios.com site.
    Those folks work on nothing but old radios.

    I dunno about that place. I seem to recall at least one person of low, questionable morals, who frequents
    that place....


    Best approach if one were to want to sell them, photograph the lot (ends of the boxes typically have
    the numbers on them) and advertise them accurately, as coming from this place, completely untested
    and uknown condition.

    Best ones have only four of five pins on the bottom....

  9. #108
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    Since it's a necro-thread, I won't feel bad about taking it afield a bit:

    Is there any demand among collectors for large (like, a foot tall and 8" around or so) vacuum tubes? I don't have a picture of it here, but I kept such a tube from my "working at the 'tute" days, and since it's just taking up space I was thinking of Ebaying it. But any actual knowledge of such things (even if it's the dreaded Steampunk route) would be helpful.

  10. #109
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    Quote Originally Posted by Milland View Post
    Since it's a necro-thread, I won't feel bad about taking it afield a bit:

    Is there any demand among collectors for large (like, a foot tall and 8" around or so) vacuum tubes? I don't have a picture of it here, but I kept such a tube from my "working at the 'tute" days, and since it's just taking up space I was thinking of Ebaying it. But any actual knowledge of such things (even if it's the dreaded Steampunk route) would be helpful.
    Depends on what it is. Does it have a number or can you post a picture? It is likely a transmitting tube and the value can be from nothing to a kilobuck.

    Bill

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    Milland, you need to post the tube number. Sounds like a 6C21 radar modulator.

    You could try these guys. I got some tubes from them when I repaired a TEK 4 channel plugin.

    VIVA TUBES [[email protected]]

    Tom

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    Hi guys,
    Thanks for the response! I'll be able to post some pics later, when I get back to the shop (no rest for the weary). I actually have the box and ancient straw packing for it too, that must increase the value ten-fold!

  13. #112
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    How memory fails! I was sure the tube (in a nice big 8" x 8" x 18" box) was larger and "more ornate", but after checking fifteen years later it's not as I remembered. It's about 9" tall and around 5" diameter on the largest part of the glass.

    It's a power tube of some form, for a high voltage supply from the 70's or earlier. Going by markings etched in the base (doesn't seem like a great idea to vibro pen a vacuum tube), it was installed in 1975, and must have been removed and/or replaced sometime later. The lab was going through a cleanup when I decided to keep it rather than trash it, and by then the HV supply must have already been removed.

    Here's some pictures of it, there is deterioration (sulfidization?) of the top electrode, and I didn't clean off any of the small debris from the tube body. It is a single-wall construction, there's a nice lensing effect from the tube wall that makes it look doubled.

    Pretty sure from the part number that it's a thousand amp capacity, I suspect that the tube testers that RadioShack had didn't offer pin positions for it...
    p3310001.jpgp3310003.jpgp3310006.jpgp3310004.jpgp3310005.jpg

    Edit: Found what looks to be the identical tube on Ebay: Vintage Eimac JAN 8166 Forced Air Cooled Transmitting Tetrode Tube Premium Valve | eBay

    Edit2: Tube 4-1000A / 8166 seems to indicate my guess of 1000 amps capacity was off base, but it has a plate dissipation max of 1000W. Still a good handful...

  14. #113
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    William Eitel and Jack McCullough worked for a transmitting tube manufacturer in the 1930s. They proposed some improvements, unfortunately in a less than diplomatic manner, and got themselves fired. They started their own company and developed some very successful tubes, notably ones like the 250TH triodes that were used in the BC610 transmitters that supplied communications for the European invasion in WWII. During the war they worked on some improved tubes which they called radial beam tetrodes but were too busy supplying their production to bring them to market. In a backhanded way, that turned out to be in their advantage. With the invasion of Japan looming, everyone was turning out war materials as fast as possible when the war ended with the atomic bombings. All that extra material went on the surplus market for prices next to nothing, enabling a 17 year old like me to build a transmitter with three type 304 tubes, originally designed as RADAR pulse tubes, which I could buy for $5 each on a carhop's pay instead of the hundreds they would normally cost. Great for high school kids but a disaster for manufacturers. Eitel-McCullough had very large production facilities, courtesy of the war department but they were paid on a cost plus basis that left them with little cash and a completely dead market. They brought the prototype radial beam tetrodes up to production status, the first being designated 4-125A. That gave them a product that affluent people would buy instead of the older designs. The 4-125A was so successful that they scaled it up and down, the 4-65A, 4-250A, 4-400A and your tube, the 4-1000A. They were so much more efficient and easier to use that they eclipsed the older triodes.

    Here is mine in my living room display. The large tube to the right is one of the transmitting tube types used in the English Chain Home RADAR system during the Battle of Britain. The black box is the case for my Vibroplex key and the rectangular frame on the left is a magnetic core memory.

    I need to do some arranging.

    Bill

    ATTACH=CONFIG]253555[/ATTACH]
    Attached Thumbnails Attached Thumbnails tube.jpg  

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  16. #114
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    And the small tipped tennis ball tube in the mid foreground, western electric?

    Two of those are visible on the shelf in my old office:



    Those were from an old WE audio amplifier, one was used with the grid and plate tied together, as the rectifier!

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  18. #115
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    [QUOTE=jim rozen;3338241]And the small tipped tennis ball tube in the mid foreground, western electric?/QUOTE]

    No, a WWII German dual triode from the Warren Johnson collection. A stranger came into an antique wireless meeting and asked who collected tubes. People pointed at me and he said he had a lot of tubes to sell. I wound up buying them all. There were all sorts of strange tubes, some with smoke residue and scotched labels. It seemed that Warren liberated them from a junkyard, then later committed suicide. I had corresponded with Warren's co-conspirator on some EBAY transactions so I looked him up at the next Antique Wireless convention in Rochester NY and got the backstory.

    After WWII the army shipped a lot of German equipment to the US for evaluation. When they got done, they put it on the surplus market and a junkie in Fort Wayne, Indiana got it. He was crushing it, including the tubes, just for the metal content. Warren and his pal, who I will just call Mike, climbed the fence at night and took all the tubes they could carry. Mike sold most of his but Warren kept them and added over the years. Then he got in some sort of dispute with his his landlady (that is all I know), set the house on fire and shot himself with a gun Mike had sold him, which didn't do Mike's mental state any good. Mike had moved out of the area and was not involved from there on. A neighbor got permission to salvage what he could from the house and when he came to St. Louis because his son was going to college here, brought the tubes to sell. It was a wild mix with things like low powered magnetrons used for local oscillators and various transmitting tubes marked "Wehrmacht" and "Kreigsmarine". They survived the trip in a car trunk with no padding fairly well, although the filaments in all the "French" tubes like La Radiotechnique triodes were broken the same way. They must have had a resonance with the car vibration. There was a book from a German airborne RADAR experimental station and some of the tubes were from there, pictured in the book.

    Bill

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  20. #116
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    That;s a wild story, and some interesting stuff.

    I have nothing mire exciting in the various boxes of tubes than a few 813s, some ancient US types, and a few lighthouse HF tubes. I guess I am just not a 'collector" in that sense, I accumulate things that look potentially useful, and I do not necessarily get rid of them when my interest in that area decreases.. Sometimes I do. I had an audio oscillator of a type that was HP's very first product, and an HP tunable voltmeter from the war years, but sold them to gain space, they were big, and not that useful after I obtained newer stuff..


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