Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: adydula on August 05, 2015, 08:44:47 AM
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Ok please don't shoot me. I spent a few hours looking on the forum and at headfi.
I got 2 12AT7's coming tomorrow from an ebay seller that was sending me 5963's he "upgraded" my order to these "rare" Sylvania 12AT7's...which from what I read have a high gain and aren't really a good thing to run in the crack.
So I thought I found a thread the other day on the forum where some folks have installed resistors on the speedball boards to allow the plate voltages to be within tolerance so they can be used...even though this would cause the other normal tubes to be out of their optimal voltages?
So the long story short, is there a simple resistor value change to allow the 12AT& to run or not??
If there is a thread that I have missed would you please point me to it or shuld I just return the tubes?
Thanks
Alex
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http://bottlehead.com/smf/index.php?topic=4295.0
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Your e-bay seller "upgraded" you to the wrong tube. I'd send them back.
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The 5963 has only slightly higher gain than the 12AU7, might give it a try
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OK thanks,, I saw the FAQ, it kind of indicates it will work with no detriment except the volume control would be pretty much unuseable due to the high gain.
Think I will ask the ebay guy to replace rather that modify for one tube and mess with another!!
Thanks
Alex
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2wo sorry u posted as I was updating...yeah I have tried the 5963's they work fine and sound great,,, its the 12AT7's that I am worried about working properly etc..
Alex
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5963 is fine, it is a computer grade 12AU7. 12AT7 is the wrong tube, and it is not a sub nor an upgrade for a 5963.
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Thanks Doc!
I am listening to the old Sylvania 5963 and its driving the old RCA coke bottle 6AS7G...absolutely stellar sound....gosh you guys make some great stuff....the snappiness of the sound listening to some old Spyrogyra is stunning to say the least...the 12AT7's are headed back!
Alex
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If you ever find any Sylvania 5963 with "JAN US NAVY" written on them in gold lettering snap them up, to my ears they are some of the best sounding 12au7 variants.
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Will do I have 2 more coming and they are Sylvania but dont know if they are JAN or not..
I do volunteer work in a WWII Battleship and have crawled around it and in the electrical repair shops closed to the public I have seen many NOS tubes from the late 30's and 40's still in their cartons never yet opened ans used!!! OMG its really neat to see these, but they will never be used as they are part of a national treasure....
Alex
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That sounds amazing, i would love to explore an old battleship like that. I guess you could say those tubes are being used, or preserved for future generations :)
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Being in a navy town the story that always comes up is how tube gear on ships got retubed every three months and the electronics techs would use the pulled tubes for skeet practice off the fantail when they were at sea.
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Trapped on a ship, have ammunition, yup sounds reasonable to me :)
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Had the chance to look around USS North Carolina many years ago pre Cher :o the scale of the ship is damn impressive.
https://www.youtube.com/watch?v=5G4O5AMSevc (https://www.youtube.com/watch?v=5G4O5AMSevc)
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Yup thats my ship!
I have crawled around the ship into many compartments that are closed to the public doing research on the fire control systems, specifically how the 16: main guns were designed and worked from the actual firing circuits, switchboards, power and the mechanical - analog computers or range keepers. Its amazing how the technology at that time was used to generate a predictive future firing solution with analog mechanical computers and vacuum tubes!!
In the ship there are vertical gyroscopes used for meany thing called Stable Verticals and Stable Elements which had a free spinning gyroscope with a AC electro-magnet mounted on top of it which two coils of wire mounted in a gimbal arrangement that moved with the ships pitch and roll, as these coils moved and cut the magnetic fields of the electromagnet a voltage/current, small...was induced and was sent to follow up circuits to be used to help keep the gyro stable. Tubes like 6A6 dual triodes were used in the amps and C6A's used as grid controlled rectifiers..and many others.
There are boxes labeled with the company, like Westinghouse and many tubes have just numbers on them....I will one day take an inventory down there and help preserve them in the ships archive. Even back then each tube carton has the actual government contract number on it!!
I have been able to look at the actual blueprints and circuit diagrams and schematics from when the ship was built starting back in 1938. Its like a time capsule!
Alex
Note: The guy who said he sent me 12AT7's replied to me that he was incorrect and he sent me 5693's!!! Ha! He made a mistake in his communications with me with a customer that actually bought 12AT7's!!
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Alex,
As someone who lives in North Carolina I just want to send a BIG thank you to you for all the work you do preserving the USS North Caroilina. I have toured the ship a couple of times. And I have spent the weekend on the USS Yorktown aircraft carrier in Charelston SC with the scouts. I can't thank the men and women enough who preserve these national treasures for us. They are time capsules and examples of living history.
THANK YOU!!!
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Thanks so much... its an honor to me to do this... my uncle was a Marine in the 4th Div, 25th Marines on Iwo Jima and survived, the USS North Carolina was there supporting him and all the rest of our troops. He passed away this year. It was his journey that started me researching what happened and eventually the BB55 came into play and the opportunity presented itself to become a volunteer.
Its a lot of fun and work... painting, repairing, and restoring.
Maybe someday we may meet on it in Wilmington
All the best....
Alex
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Hi Alex, getting to have a wonder round the ship was a not to be missed opportunity for me and definitely a memorable moment.
In my teens I became fascinated by the old battleships classes and read all I could get my hands on after finding out my own grandfather (whom I never knew) served on HMS Rodney a British 16" gun battleship during the hunt for the German Bismarck.
I find it simply mind blowing when thinking about how these huge ships where designed and constructed in the past without all the modern machinery and computers we have now.