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Old 27th April 2010, 02:15 AM   #1
jfitz57 is offline jfitz57  United States
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Default Tube bases and plate caps rant

HI!

OKAY, I'm half a century old now and I started out fixing tube stuff but been away from it for a long time.

I'm really only interested in the all glass tubes I have seen.

Can anyone tell me why 7 and 9 pin miniature tubbes have .040" pins?
Thats so close to 1mm. where they developed in otside of the U.S.A.?

I read that MAGNOVAL's were developed by Western Electric aroud 1956 and use .050" pins (both 'merican).

NOVARS's are the same except they hav .040 (1mm) pins. Did they come after MAGNOVAL's?

The connector on the top of a tube is caled a "Plate Cap".

The thing you need to atach it physically and electrically is called a "Plate Cap".

Tube Data Sheets I have looked at show mostly "Miniature Skirted Caps" and "Small Caps".

The web sites that sell plate Caps sell "small" "medium" and "large".

Now I think I need "small" plate cap (connectors) to fit the "miniature" plate caps on the tubes I have.

And I know the MAGNOVAL tubes I have will fit into the "9-pin-compactron" sockets I have (even though there is no such thing as a 9-pin-compactron) but after doing that a NOVAR tube will not fit because the socket will be expanded by the .050" pins and be to loose for .040" pins.

Took me about 2 months to 'figer' this out!

Hope it helps, would like to here from anyone whe been there and beyonde.

Jim
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Old 27th April 2010, 03:33 AM   #2
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A 6GF7 is a perfect example of a 9-pin compactron - there are many others, and they are far more common than the magnoval tubes -a good tube manual will show you. The Chinese "small" plate caps are not well suited for the skirted caps common on many of the smaller compactron sweep tubes (and some octals) - they sit up high and look dorky, if they fit at all. At one time, there were bakelite tube caps available that addressed this, but I've never seen any of them on the NOS market. The big compactron sweep tubes take a "medium" cap, as far as I've seen, though most of the new Chinese medium caps are a P**s-poor (loose) fit, and the contacts fall out at the drop of a hat. The old Millen and National caps are much nicer if you can find them.

If you look carefully, you can find sockets specifically for Magnoval tubes. I have no Idea how they came up with the standards for pin size - I just scramble to find sockets that fit.
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Old 27th April 2010, 01:48 PM   #3
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Quote:
though there is no such thing as a 9-pin-compactron........A 6GF7 is a perfect example of a 9-pin compactron
Who is right here? Both people are.

GE registered the name "Compactron" to refer to their new 12 pin multiple section tubes. If you look through the GE literature you will find that there are no 9 pin compactrons. Since GE owned the trademark you won't find any "Compactrons" in the RCA tube manual. RCA called them duodecars. Tung Sol used the Compactron name.

I was working in a TV repair shop through my high school years (1967 - 1970) and we (and just about anyone else) referred to all of these new funny looking baseless tubes as "Compcatrons". That practice was adopted by the electronics magazines and GE did nothing to stop it so the name stuck.

It was also common practice for tube manufacturers to make tubes for each other so it is possible to find a tube with the word Compactron printed on it and a brand name other tham GE. I don't believe that I have ever seen the word Compactron printed on a 9 pin tube though.
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Old 28th April 2010, 03:27 AM   #4
jfitz57 is offline jfitz57  United States
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I have found a place that sells 1/4 inch spring clips for $0.75 each but there minimum order is $25. Anyone know of another source?
This amp looks like it uses the Chinese caps and it looks OK to me

http://www.ne.jp/asahi/evo/amp/el509/intro.htm

Jim

Last edited by jfitz57; 28th April 2010 at 03:32 AM.
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Old 28th April 2010, 03:38 AM   #5
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You can see the metal pate cap skirt below the ceramic plate cap - dorky - the equivalent of "flood" pants in electronics. Plus, I've found the new build Chinese plate caps just don't grip all that well. The "large" caps may be better, as they made some attempt to duplicate the 4-point contact of the NOS caps. I'll try one on an 813 and see...
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Old 28th April 2010, 04:04 AM   #6
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Originally Posted by wrenchone View Post
You can see the metal pate cap skirt below the ceramic plate cap - dorky - the equivalent of "flood" pants in electronics. Plus, I've found the new build Chinese plate caps just don't grip all that well. The "large" caps may be better, as they made some attempt to duplicate the 4-point contact of the NOS caps. I'll try one on an 813 and see...
I got some of the large ones for a couple of 812A that I have and they fit great - the first time. Second fit is looser, which is worrying. Obviously the material in the sprung part is made of too soft metal.
In my corner of the world, they are all that is available

Gary
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Old 28th April 2010, 04:47 AM   #7
jfitz57 is offline jfitz57  United States
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Originally Posted by wrenchone View Post
You can see the metal pate cap skirt below the ceramic plate cap - dorky - the equivalent of "flood" pants in electronics.
HAHA! dorky will be OK for this time. I just want to make something (different) with tubes. The tubes I got are 29KQ6/PL521's. They have some interesting characteristics like 29V 300mA heaters and +-240V heater to cathode. I can string 4 of them in series and not need a heater trandformer.
Paid $10 for 10 tubes so I can afford to experiment. HECK, I only got a DMM and a soldering iron 2-3 months ago.

Jim
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Old 28th April 2010, 04:50 AM   #8
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What really bugs me is that the metal contacts on the small and medium plate caps often fall out and get lost before you can use them - not exactly a ringing endorsement. I use NOS or UOS caps when I can because of this and the loose (and ever loosening) fit. I'm looking to use some kind of fuse clip for the the small-sized caps, though it will force me to machine some sort of shroud to cover the contacts.

This issue is why I haven't been really eager to start on my SE screen-driven 6P45s amp.

Last edited by wrenchone; 28th April 2010 at 04:51 AM. Reason: sp
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Old 28th April 2010, 05:16 AM   #9
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Originally Posted by wrenchone View Post
What really bugs me is that the metal contacts on the small and medium plate caps often fall out and get lost before you can use them - not exactly a ringing endorsement. I use NOS or UOS caps when I can because of this and the loose (and ever loosening) fit. I'm looking to use some kind of fuse clip for the the small-sized caps, though it will force me to machine some sort of shroud to cover the contacts.

This issue is why I haven't been really eager to start on my SE screen-driven 6P45s amp.
Fuse clips, there's a possibility. Check out the places that sell big car audio stuff. I'll bet you will find gold or silver plated ones up to at least 1/2".
And for a shroud, again from the auto electrical world there are boots designed to fit over ignition coil pack input leads, and alternator leads to keep moisture out (and mechanic's spanners!). Not designed for HV use, so would have to be insulation tested, but they are designed for hot engine areas. They are soft (silicone?), so would snug down on the tube nicely.
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Old 28th April 2010, 05:35 AM   #10
jfitz57 is offline jfitz57  United States
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Originally Posted by wrenchone View Post
This issue is why I haven't been really eager to start on my SE screen-driven 6P45s amp.
Never heard of a 6P45S so I googled it. 6P45S/EL509/6KG6
I really don't get the SE thing but I can see that LOTS of people do.
I was searching today and ran across the J J Electronics EL509.
Looks to me like a sweep tube stuffed into an octal based bottle.
Don't have a link, sorry. Are you a machinist? (been there)

Jim
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