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Old 5th December 2012, 01:30 PM   #1
Bigun is offline Bigun  Canada
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Default 2A3 mounted horizontally

According to RCA datasheet it's 'permissible' to mount it horizontally providing the filament is in a horizontal plane.

Anybody actually done this - any issues ?

I asked manufacturer of JJ-2A3-40 and they don't recommend it for a 2A3 or 300B from any manufacturer.

The reason for asking is that horizontal mounting provides another option, some flexibility in the physical construction of a project.
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Old 5th December 2012, 02:33 PM   #2
tinitus is offline tinitus  Europe
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what a shame

how about 45degr angling instead it would at least look more weird than stupid
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Old 5th December 2012, 02:55 PM   #3
kmaier is offline kmaier  United States
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The Fi X 2A3 amplifier has them mounted sideways. I would suggest allowing for the sockets to be rotated a bit as I've not seen too many 2A3 tubes that always line up properly to the base pins as noted in the datasheet.

Personally, I still prefer them mounted vertically, but for NOS tubes, it was a supported practice.

Regards, KM
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Old 5th December 2012, 03:01 PM   #4
oshifis is offline oshifis  Hungary
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45 angling?

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Old 5th December 2012, 03:21 PM   #5
Bigun is offline Bigun  Canada
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So for NOS, it's not an issue and I've heard no bad things about the fi.

I may ask JJ specifically about the Fi 2A3 and suitability of the JJ 2A3 40

the 45 degrees options looks cool - looks like missile launchers !
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Old 5th December 2012, 03:49 PM   #6
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I always thought the filament was supposed to be vertical, not horizontal.

If it's horizontal, it might sag to the bottom, and touch the grid (or change the operating parameters significantly). If it's vertical, if it sags, it won't touch any other element.
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Old 5th December 2012, 04:58 PM   #7
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Quote:
Originally Posted by oshifis View Post
45 angling?
With indirectly heated cathods like the EL34 it doesn't much matter.

Quote:
Originally Posted by MrCurwen View Post
I always thought the filament was supposed to be vertical, not horizontal.
Yes, you are absolutely correct.
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Old 5th December 2012, 05:15 PM   #8
kmaier is offline kmaier  United States
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Default don't shoot the messenger

Well, according to the RCA data sheet published October 15, 1947, the accepted mounting position (for the 2A3) was changed to "Any". This would also account for the slack in the alignment spec for the base pins to filament. I've noticed the same on many 45 triodes.

Regards, KM
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Old 5th December 2012, 05:57 PM   #9
Bigun is offline Bigun  Canada
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the RCA sheet I have was specific about orientation, but a Tung Sol data sheet said 'Any'. My conclusion is that it's safe for NOS, but there's no harm following the recommendation in the original RCA for orientation. If I remember it was to keep certain pins in a horizontal plane not the grid so it may be that it means the filament is vertical.

However, I'm interested in a modern 2A3. I can't see why these tubes would be less suitable for horizontal mounting - but I don't know and am still curious ? I notice that there are reviews on the internet for the JJ 2A3 in the Fi 2A3.
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Old 5th December 2012, 06:46 PM   #10
TheGimp is offline TheGimp  United States
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I suspect that the later data sheet referred to the tubes using sprung filaments. I have an older 6A3, and a couple of 6B4Gs with slightly larger cross section (rectangular) filaments that are not sprung. I suspect these might be more prone to sag in some positions.

Here is what mean by sprung and unsprung.

The one without the tension arms (unsprung) has a larger cross section filament.
Attached Images
File Type: jpg sprung2.JPG (54.8 KB, 129 views)
File Type: jpg Unsprung.JPG (77.9 KB, 125 views)

Last edited by TheGimp; 5th December 2012 at 06:54 PM.
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