DO-35 diode inside vacuum tube ?

pjp · 8th February 2009, 03:37 AM

Well not really!

But what is this thing that looks like a DO-35 diode inside the glass
envelope of a vacuum tube: http://www.r-type.org/pics/aaa0772b.jpg

(Like to page: http://www.r-type.org/exhib/aaa0772.htm )

Miles Prower · 8th February 2009, 04:01 AM

^^

Looks like a fuse.

pjp · 8th February 2009, 04:18 AM

The 'fuse' is not accessible. If it blows you'll have to throw out the tube.

Is there some seriously catastrophic scenario that needs such extreme protection ?
(I'm a tube noob)
(if it is a fuse, its protecting the gate)

astouffer · 8th February 2009, 04:18 AM

Quote:

Looks like a fuse

How is the fuse changed when it decides to blow

Richard Ellis · 8th February 2009, 04:23 AM

Its' a small signal RF diode............the kind we all used making our first AM radios!!
__________________________________________Rick.... ....

Robert McLean · 8th February 2009, 02:55 PM

Looking at the close up view in the last picture on the page here
http://www.r-type.org/exhib/aaa0772.htm

it appears to me to be some sort of mechanical support or stiffener. The lead going through it does not seem to actually go anywhere, it seems to be curved like a spring and is pressing against the bottom structure. Perhaps it reduced microphonics ??

If it was electrically connected somehow that I cant see then perhaps it is some sort of spark gap protection ??

pjp · 8th February 2009, 07:47 PM

It isn't a support.
Its the only connection to the grid (gate).

kevinkr · 8th February 2009, 08:55 PM

Quote:

Originally posted by pjp
It isn't a support.
Its the only connection to the grid (gate).

It appears to me that it goes to pin 5 which is open, and the thin line through it appears to be nothing more than a distorted image of a lead behind it. To me it appears to be nothing more than a support. (I'm using a very good CRT monitor and image magnification and that is what it looks like to me.)

Tubes have grids, fets of various descriptions have gates.

pjp · 9th February 2009, 01:20 AM

Quote:

Originally posted by kevinkr
It appears to me that it goes to pin 5 which is open

Now its beginning to make sense to me - perhaps the purpose is to provide mechanical support without the inductance of a lead (at VHF) ?

Is such a mechanism employed in any other tube ?

refference · 9th February 2009, 02:33 AM

Quote:

Originally posted by pjp

................ mechanical support without the inductance of a lead (at VHF) ?

I don't think so . The purpose is to provide INSULATION , between the internal electrode where it is connected and the
external pin 5 .

kevinkr is correct !!

Regards ,

Carlos

8th February 2009, 03:37 AM	#1
pjp diyAudio Member Join Date: Nov 2006 Location: under the rainclouds	DO-35 diode inside vacuum tube ? Well not really! But what is this thing that looks like a DO-35 diode inside the glass envelope of a vacuum tube: http://www.r-type.org/pics/aaa0772b.jpg (Like to page: http://www.r-type.org/exhib/aaa0772.htm )

8th February 2009, 04:01 AM	#2
Miles Prower diyAudio Member Join Date: May 2005 Location: USA Blog Entries: 2	^^ Looks like a fuse. __________________ There are no foxes in atheistholes www.dolphin-hsl.com

8th February 2009, 02:55 PM	#6
Robert McLean diyAudio Member Join Date: May 2005 Location: Stittsville, Ontario, Canada	Looking at the close up view in the last picture on the page here http://www.r-type.org/exhib/aaa0772.htm it appears to me to be some sort of mechanical support or stiffener. The lead going through it does not seem to actually go anywhere, it seems to be curved like a spring and is pressing against the bottom structure. Perhaps it reduced microphonics ?? If it was electrically connected somehow that I cant see then perhaps it is some sort of spark gap protection ?? __________________ Robert McLean

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8th February 2009, 04:18 AM	#3
pjp diyAudio Member Join Date: Nov 2006 Location: under the rainclouds	The 'fuse' is not accessible. If it blows you'll have to throw out the tube. Is there some seriously catastrophic scenario that needs such extreme protection ? (I'm a tube noob) (if it is a fuse, its protecting the gate)

8th February 2009, 04:23 AM	#5
Richard Ellis diyAudio Member Join Date: Sep 2006 Location: Mar del Plata, a BIG seasonal getaway city, can see the Ocean from our residence.	Its' a small signal RF diode............the kind we all used making our first AM radios!! __________________________________________Rick.... ....

8th February 2009, 07:47 PM	#7
pjp diyAudio Member Join Date: Nov 2006 Location: under the rainclouds	It isn't a support. Its the only connection to the grid (gate).

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