Warning: Creating default object from empty value in /homepages/11/d132647312/htdocs/Amfone/mkportal/include/SMF/smf_out.php on line 47
3-500Z Infrared Radiation




 
The AM Forum
August 17, 2022, 03:14:37 AM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: [1] 2   Go Down
  Print  
Author Topic: 3-500Z Infrared Radiation  (Read 1697 times)
0 Members and 1 Guest are viewing this topic.
KD1SH
Member

Offline Offline

Posts: 427



« on: July 25, 2022, 07:57:23 PM »

   Have my chassis and most of the parts for my first big retirement project - a triple 3-500Z amp - and started laying out the sockets, chimneys, tank components, filament transformer; to see what fits where. The tubes will be laid out in a triangle, with the plate choke in the center.
   Started thinking, though: the 3-500Z disposes of most of its heat through infrared radiation, which will simply be what it is regardless of how much air I force through the chimneys. For obvious reasons I've never actually stuck my hand inside my current 3-500Z amp while it's at full battle roar, so I don't know... how much infrared radiation do those things generate? Would there be a danger of melting the insulation on the windings of my plate choke, nestled in between those three tubes? Also, I'd like to put a viewing window on the front panel, to enjoy that wonderful glow. If that window - probably acrylic - is only an inch or so from the tubes, might it melt? I suppose I could strategically place a few additional cooling air holes if needed.
Logged
W1ITT
Member

Offline Offline

Posts: 513


« Reply #1 on: July 25, 2022, 08:39:42 PM »

https://www.ebay.com/itm/233890332545?hash=item3674f33f81:g:SqsAAOSwQY9eJPvU

This is a sort of glass called "Robax".  It's made for wood stove windows and you can find other sizes.  But, given how Drake and Heath and all the others shoe horned tubes into their amplifiers, I wouldn't worry too much about heat melting things as long as you use proper air.  But a peekaboo window is the essence of coolness for glass envelope tubes.
73 de Norm W1ITT
Logged
KD1SH
Member

Offline Offline

Posts: 427



« Reply #2 on: July 26, 2022, 07:53:09 AM »

   Indeed, the physical layout seems half the battle, and the commercial manufacturers have it down to an art. Of course today it's all CAD, but my Heath SB-221 certainly wasn't done that way, and it amazes me how everything is so tightly packed.
   I'm building my amp on a 17" X 14" chassis, and even though the power supply will be external, it still requires some serious planning to get everything to fit comfortably. Like storage space, or car trunks, it looks huge until you start putting stuff into it.
   That Robax piece is 3" X 5"; should be just about right. Thanks -

https://www.ebay.com/itm/233890332545?hash=item3674f33f81:g:SqsAAOSwQY9eJPvU

This is a sort of glass called "Robax".  It's made for wood stove windows and you can find other sizes.  But, given how Drake and Heath and all the others shoe horned tubes into their amplifiers, I wouldn't worry too much about heat melting things as long as you use proper air.  But a peekaboo window is the essence of coolness for glass envelope tubes.
73 de Norm W1ITT
Logged
K9MB
Member

Offline Offline

Posts: 184


« Reply #3 on: July 26, 2022, 11:47:53 AM »

  Have my chassis and most of the parts for my first big retirement project - a triple 3-500Z amp - and started laying out the sockets, chimneys, tank components, filament transformer; to see what fits where. The tubes will be laid out in a triangle, with the plate choke in the center.
   Started thinking, though: the 3-500Z disposes of most of its heat through infrared radiation, which will simply be what it is regardless of how much air I force through the chimneys. For obvious reasons I've never actually stuck my hand inside my current 3-500Z amp while it's at full battle roar, so I don't know... how much infrared radiation do those things generate? Would there be a danger of melting the insulation on the windings of my plate choke, nestled in between those three tubes? Also, I'd like to put a viewing window on the front panel, to enjoy that wonderful glow. If that window - probably acrylic - is only an inch or so from the tubes, might it melt? I suppose I could strategically place a few additional cooling air holes if needed.

Seems like every vacuum tube emits heat as infrared, though there is light of other colors that must be converted to heat somewhere in the enclosure.
The purpose of the air is to keep the envelope temperature of the tube within bounds so that seals do not fail or the envelope melt. The seals are the primary concern on internal anode tubes, I think.
Moving air through the cabinet does remove heat, and it does it in a way to also protect the tube.

If you are concerned about the plate choke over heating, you could put a brightly polished aluminum tube shield around it that has a bakelite or teflon tube liner and put some small holes at the bottom around the perimeter from below to allow air to be pushed upward to keep the inside cool and also some holes around the outside to cool the aluminum surface cool and if you have pressurized below the chassis, the airflow will be automatic. Aluminum has very high emissivity, so it will re-radiate the energy very fast and the insulation will shield the choke a lot cooler. Limit tue top height to prevent arc overs to the plate circuit.
Logged
W1RKW
Contributing
Member
*
Offline Offline

Posts: 4326



« Reply #4 on: July 26, 2022, 02:44:21 PM »

Infrared is a radiated heat. It seems counter intuitive but why not flat black shielding to absorb the radiated heat rather than reflect it back into the tubes? 
Logged

Bob
W1RKW
Home of GORT. A buddy of mine named the 813 rig GORT.
His fear was when I turned it on for the first time life on earth would come to a stand still.
K9MB
Member

Offline Offline

Posts: 184


« Reply #5 on: July 26, 2022, 04:18:32 PM »

I believe that infrared light is nothing more than electromagnetic energy with a wavelength of about 1/1000 meter.
All electromagnetic energy and therefore all light has energy and when it is absorbed, it can produce a rise in temperature. Seems like the main culprit in sunburn is ultraviolet light.
Infrared is not visible, but it is perceived because as heat when it is absorbed by our skin.
If you look at the light used in laser cutters, there are a number of colors and the essential thing is that the light used must be coherent (all of one color), but any of the laser colors can cut thick metal plate.
We use microwaves at about 4Ghz to cook food because those frequencies are efficiently absorbed by water.

The use of a flat black surface  allows the absorption of all colors of light but what comes next is the important thing. Black surfaces are efficient radiators of infrared heat unless the heat is transferred outside the environment and that can be accomplished by immersing the reverse surface in a liquid or just use the fluid of air. For air, the transfer is made more efficient by increasing surface area and that usually means fins and then airflow on the fins remove the heat energy so that the molecules are not vibrating at frequencies that cause infrared energy to be emitted.
Because aluminum has high emissivity, it efficiently radiates energy and is almost as good as copper in conducting heat.
For the amplifier, it might be best not to focus on the wavelength of the extraneous energy produced by the tube, but to remove the excess heat energy as efficiently as possible and to shield ant components that are sensitive to high temperatures, as well. 73, MB
Logged
KD1SH
Member

Offline Offline

Posts: 427



« Reply #6 on: July 26, 2022, 05:59:38 PM »

Makes sense. I've seen that suggested somewhere, but I can't remember where. Maybe one of Orr's "West Coast" handbooks. I do intend to provide some aluminum shielding between the tubes and the filament transformer, since it'll be delivering 45 amps to the three filaments and certainly generating significant heat of its own. The tank components: caps and inductor, probably won't be too bothered by the heat, although my plate tune cap will be a Jennings vacuum variable and it's probably best not to bake it too much. My current layout has that cap quite a ways from the tubes, anyway. Depending on what sort of air-variable cap I decide to use for the loading cap, I may have to pad it a bit with a fixed cap - probably a large transmitting type mica - and I'll try to avoid exposing that to the heat as well.

Infrared is a radiated heat. It seems counter intuitive but why not flat black shielding to absorb the radiated heat rather than reflect it back into the tubes? 
Logged
WBear2GCR
Member

Offline Offline

Posts: 4108


Brrrr- it's cold in the shack! Fire up the BIG RIG


WWW
« Reply #7 on: July 30, 2022, 12:58:13 PM »

Assuming you are going to blow air up and through, over the tubes and out the top, there is nothing at all to worry about.

IF you are not planning on pressurizing the chassis, using chimneys, imho that would be a mistake.

                                   _-_-bear
Logged

_-_- bear WB2GCR                   http://www.bearlabs.com
KD1SH
Member

Offline Offline

Posts: 427



« Reply #8 on: July 30, 2022, 01:09:32 PM »

Eimac air-system sockets; Eimac chimneys; blower big enough to push the tubes out of their sockets; no worries about glass envelopes or seals. More concerned about the IR radiation from three tubes shining right onto my plate choke. Shouldn't be a problem - commercial builders jam everything in there pretty tight, and nothing melts (usually). I'll have air to spare; probably place a few small holes around the base of the plate choke.

Assuming you are going to blow air up and through, over the tubes and out the top, there is nothing at all to worry about.

IF you are not planning on pressurizing the chassis, using chimneys, imho that would be a mistake.

                                   _-_-bear
Logged
DMOD
AC0OB - A Place where Thermionic Emitters Rule!
Contributing
Member
*
Offline Offline

Posts: 1663


« Reply #9 on: July 30, 2022, 07:58:34 PM »

   Have my chassis and most of the parts for my first big retirement project - a triple 3-500Z amp - and started laying out the sockets, chimneys, tank components, filament transformer; to see what fits where. The tubes will be laid out in a triangle, with the plate choke in the center...

The critical concern is conducted heat to the filament pins. Air flow around those base pins and using silver solder solves a lot of problems.

Phil - AC0OB
Logged

Charlie Eppes: Dad would be so happy if we married a doctor.
Don Eppes: Yeah, well, Dad would be happy if I married someone with a pulse.NUMB3RS   Smiley
KD1SH
Member

Offline Offline

Posts: 427



« Reply #10 on: July 30, 2022, 08:09:42 PM »

The Eimac sockets by design give good airflow around the pins, but I like the idea of silver solder. Great idea.


The critical concern is conducted heat to the filament pins. Air flow around those base pins and using silver solder solves a lot of problems.

Phil - AC0OB
Logged
w8khk
Member

Offline Offline

Posts: 1126


This ham got his ticket the old fashioned way.


WWW
« Reply #11 on: July 30, 2022, 10:20:39 PM »

The Eimac sockets by design give good airflow around the pins, but I like the idea of silver solder. Great idea.

Good airflow around the base pins IS MOST IMPORTANT.  I recall a phone discussion years ago with Bill Orr, who wrote most of the "Care and Feeding of Power Grid Tubes" document.  He cautioned against making additional holes in the chassis around the periphery of the socket.  He said that many hams make the mistake of adding these holes, thinking that the bulb and top seal need more cooling air than what can flow through the socket and tube base.  But these additional holes actually reduce the cooling of the base seals and pins, where it is needed the most.  I asked him about using one or two 4-inch muffin fans to cool a pair of 4-400s in a legal limit linear amplifier.  He said that I should be fine by pressuring the chassis with a single fan if I was planning on sideband, but for RTTY, use two fans.  Let ALL the air flow through the socket and tube base.  I did as he advised, and never needed to replace the 4-400s for over 20 years, when I switched over to both sidebands and an unsuppressed carrier.
Logged

Rick / W8KHK  ex WB2HKX, WB4GNR
"Both politicians and diapers need to be changed often and for the same reason.”   Ronald Reagan
Detroit47
Member

Offline Offline

Posts: 611



« Reply #12 on: July 31, 2022, 11:29:41 PM »

The Bunker of Doom can provide you with Bill Orr's 1979 amateur service newsletters. He discusses this at length. A fountain of information thank you Patrick.

johnathan N8QPC 
Logged
K9MB
Member

Offline Offline

Posts: 184


« Reply #13 on: August 02, 2022, 01:50:26 AM »

The Eimac sockets by design give good airflow around the pins, but I like the idea of silver solder. Great idea.


The critical concern is conducted heat to the filament pins. Air flow around those base pins and using silver solder solves a lot of problems.

Phil - AC0OB

I am curious what you mean by Silver Solder?
I use two kinds:

1: For outdoor electrical connections and for soldering to amplifier coils and bandswitches, I use an alloy that is 4% silver and 95% Tin. It melts at about 435degrees F compared to 60-40 tin-lead (350degrees) It is also stronger than 60-40 or 63-37.
 2. For attaching 2AWG ground wore to my ground rods, I use a 15% silver alloy that melts at 1450 degrees that is also called silver solder. It is much stronger and pretty weather proof so connections last outside.
Os it one of these you mean? There are a lot of other alloys besides these..

Also, silver solder is not a cure all because improperly,cooled,tube bases can be compromised by the solder in the tube pins melting.
Really, ot is not a question of infrared radiation, but removing heat that is generated.
Infrared radiation is not the same as heat, even of a hot object may radiate infrared as well as visible light as energy as anyone who has seen a white hot 100th or 250th at full dissipation power will attest.
Logged
KD6VXI
Contributing
Member
*
Offline Offline

Posts: 2491


Making AM GREAT Again!


« Reply #14 on: August 03, 2022, 05:46:12 PM »

Why not use cadweld outside? 

I've installed literally hundreds upon hundreds of cadweld connections and it's painless?

You use a torch? 

--Shane
WP2ASS / ex KD6VXI
Logged
K9MB
Member

Offline Offline

Posts: 184


« Reply #15 on: August 03, 2022, 08:25:15 PM »

Why not use cadweld outside?  

I've installed literally hundreds upon hundreds of cadweld connections and it's painless?

You use a torch?  

--Shane
WP2ASS / ex KD6VXI


Are you are asking me, Shane?  I did consider cad-weld on my last job. My brother runs an electrical contracting business and they do thousands a year,  but seems like I thought it too ,expensive per shot to suit me at the time and the silver-copper alloy brazed easily with a MAP gas torch and we did a dozen that time. Running beads for 4 inches or more on the rods. Stands up,well in dirt too.
I do consider cadwelding faster, and may use it next time I need to bond a lot of ground rods to solid awg 2 ground wire.

The way this kind of thing usually works out, though is I probably paid more counting the cost of the MAP gas and the silver solder together… 😬😉
Logged
DMOD
AC0OB - A Place where Thermionic Emitters Rule!
Contributing
Member
*
Offline Offline

Posts: 1663


« Reply #16 on: August 03, 2022, 11:25:07 PM »

The Eimac sockets by design give good airflow around the pins, but I like the idea of silver solder. Great idea.


The critical concern is conducted heat to the filament pins. Air flow around those base pins and using silver solder solves a lot of problems.

Phil - AC0OB

I am curious what you mean by Silver Solder?
I use two kinds:

1: For outdoor electrical connections and for soldering to amplifier coils and bandswitches, I use an alloy that is 4% silver and 95% Tin. It melts at about 435degrees F compared to 60-40 tin-lead (350degrees) It is also stronger than 60-40 or 63-37.
 2. For attaching 2AWG ground wore to my ground rods, I use a 15% silver alloy that melts at 1450 degrees that is also called silver solder. It is much stronger and pretty weather proof so connections last outside.
Os it one of these you mean? There are a lot of other alloys besides these..

Also, silver solder is not a cure all because improperly,cooled,tube bases can be compromised by the solder in the tube pins melting.
Really, ot is not a question of infrared radiation, but removing heat that is generated.
Infrared radiation is not the same as heat, even of a hot object may radiate infrared as well as visible light as energy as anyone who has seen a white hot 100th or 250th at full dissipation power will attest.


What I was referring to was the Silver Bearing Solder of Sn42/Pb36/Ag2 which has served me well for soldering the 3-500Z "socket" connections (including the filament sockets of course) in my Henry 2K-4 and other equipment hot spots. All others melted and or crystallized.

I did not mean to infer the soldering of the actual base pins of the tube.

Phil

Logged

Charlie Eppes: Dad would be so happy if we married a doctor.
Don Eppes: Yeah, well, Dad would be happy if I married someone with a pulse.NUMB3RS   Smiley
K9MB
Member

Offline Offline

Posts: 184


« Reply #17 on: August 04, 2022, 01:18:29 AM »

The Eimac sockets by design give good airflow around the pins, but I like the idea of silver solder. Great idea.


The critical concern is conducted heat to the filament pins. Air flow around those base pins and using silver solder solves a lot of problems.

Phil - AC0OB

I am curious what you mean by Silver Solder?
I use two kinds:

1: For outdoor electrical connections and for soldering to amplifier coils and bandswitches, I use an alloy that is 4% silver and 95% Tin. It melts at about 435degrees F compared to 60-40 tin-lead (350degrees) It is also stronger than 60-40 or 63-37.
 2. For attaching 2AWG ground wore to my ground rods, I use a 15% silver alloy that melts at 1450 degrees that is also called silver solder. It is much stronger and pretty weather proof so connections last outside.
Os it one of these you mean? There are a lot of other alloys besides these..

Also, silver solder is not a cure all because improperly,cooled,tube bases can be compromised by the solder in the tube pins melting.
Really, ot is not a question of infrared radiation, but removing heat that is generated.
Infrared radiation is not the same as heat, even of a hot object may radiate infrared as well as visible light as energy as anyone who has seen a white hot 100th or 250th at full dissipation power will attest.


What I was referring to was the Silver Bearing Solder of Sn42/Pb36/Ag2 which has served me well for soldering the 3-500Z "socket" connections (including the filament sockets of course) in my Henry 2K-4 and other equipment hot spots. All others melted and or crystallized.

I did not mean to infer the soldering of the actual base pins of the tube.

Phil



I was pretty certain that you did not mean the 1450degree silver solder and that you might be using what I use that is 96% Tin and 4% silver and it melts around 435 degrees instead of 350 degrees for 60-40 tin-lead solder.

I brought it up because of all this talk about infra red radiation when the critical thing is the effective removal of heat to protect the seals and also the pin solder bonds of tubes. Because of the conflation of heat with infrared light, I was not sure that someone might silver solder braze their tube sockets. As imsane as that sounds.

Sorry if I gave you the impression that I thought you used the high temperature. Silver-copper-phosphorus alloy for tube sockets.

I have not used the alloy you mention, but no doubt it is stronger and has a higher melting point than tin-Lead solder. Did you mean 62-36-2 alloy, by the way. That is a common alloy that has 2 percent  silver?
Logged
DMOD
AC0OB - A Place where Thermionic Emitters Rule!
Contributing
Member
*
Offline Offline

Posts: 1663


« Reply #18 on: August 04, 2022, 10:39:39 AM »

...

I have not used the alloy you mention, but no doubt it is stronger and has a higher melting point than tin-Lead solder. Did you mean 62-36-2 alloy, by the way. That is a common alloy that has 2 percent  silver?

Yes, and thanks for catching that typo, as it should have been 62-36-2. I was watching late-night Perry Mason when I wrote that! Shocked

There are other new alloys out there as well with Tin-Copper-Silver mixes but I have not tried those as yet since the 62-36-2 mix has served me well.

Phil
Logged

Charlie Eppes: Dad would be so happy if we married a doctor.
Don Eppes: Yeah, well, Dad would be happy if I married someone with a pulse.NUMB3RS   Smiley
KD1SH
Member

Offline Offline

Posts: 427



« Reply #19 on: August 04, 2022, 04:41:38 PM »

  Respectfully, there's no conflating going on here. All points well taken and appreciated regarding the need to effectively remove heat from the base and anode pins. That's a given, and well documented in Eimac literature. I will be using Eimac SK-410 "air-system" sockets and Eimac SK-406 chimneys, installed per Eimac instructions, and my blower, well, see the picture attached. That blower could probably come close to literally pushing the tubes out of their sockets. I use Magnehelic gauges to read the back-pressure, and the back-pressure could easily be many times what Eimac calls for.
   My original point was that those tubes rid themselves of a great amount of heat by simply radiating it away; whether this radiation is in the form of infrared or visible light is irrelevant. When I'm in my workshop on a cold winter day, I often use a standup quartz heater - purely radiant heat - to keep warm, and that orange glow will heat me and nearby objects to an uncomfortable temperature quite quickly if a respectful distance isn't observed. But, as soon as I turn the heater off, those quartz tubes quickly cool and cease to glow. Some of that heat energy was carried away by air, but the vast majority of it was radiated away as infrared and low frequency visible light. The same thing would happen if my quartz heater was sitting in the vacuum of space with no air to carry away the heat.
   So, my original question wasn't at all about the longevity of the tubes - those design considerations will be dealt with according to Eimac literature - but rather how big a threat to nearby ancillary hardware - i.e the plate choke sitting in the middle of three glowing 3-500Z's - is that radiation? Maybe none at all, but it seemed a question worth asking.
  BTW - the blower is a "bouncy house" blower, exact specs unknown, but if I were sitting on a skateboard and holding this thing, it would send me zooming around my shop. Sounds like fun, actually; if I had more room in my shop I might just plug in a long extension cord and try that Smiley


I am curious what you mean by Silver Solder?
I use two kinds:

1: For outdoor electrical connections and for soldering to amplifier coils and bandswitches, I use an alloy that is 4% silver and 95% Tin. It melts at about 435degrees F compared to 60-40 tin-lead (350degrees) It is also stronger than 60-40 or 63-37.
 2. For attaching 2AWG ground wore to my ground rods, I use a 15% silver alloy that melts at 1450 degrees that is also called silver solder. It is much stronger and pretty weather proof so connections last outside.
Os it one of these you mean? There are a lot of other alloys besides these..

Also, silver solder is not a cure all because improperly,cooled,tube bases can be compromised by the solder in the tube pins melting.
Really, ot is not a question of infrared radiation, but removing heat that is generated.
Infrared radiation is not
I was pretty certain that you did not mean the 1450degree silver solder and that you might be using what I use that is 96% Tin and 4% silver and it melts around 435 degrees instead of 350 degrees for 60-40 tin-lead solder.

I brought it up because of all this talk about infra red radiation when the critical thing is the effective removal of heat to protect the seals and also the pin solder bonds of tubes. Because of the conflation of heat with infrared light, I was not sure that someone might silver solder braze their tube sockets. As imsane as that sounds.

Sorry if I gave you the impression that I thought you used the high temperature. Silver-copper-phosphorus alloy for tube sockets.

I have not used the alloy you mention, but no doubt it is stronger and has a higher melting point than tin-Lead solder. Did you mean 62-36-2 alloy, by the way. That is a common alloy that has 2 percent  silver?



* Blower_1.JPG (77.51 KB, 1280x960 - viewed 25 times.)

* Blower_2.JPG (79.97 KB, 1280x960 - viewed 23 times.)
Logged
K9MB
Member

Offline Offline

Posts: 184


« Reply #20 on: August 04, 2022, 05:53:30 PM »

...

I have not used the alloy you mention, but no doubt it is stronger and has a higher melting point than tin-Lead solder. Did you mean 62-36-2 alloy, by the way. That is a common alloy that has 2 percent  silver?

Yes, and thanks for catching that typo, as it should have been 62-36-2. I was watching late-night Perry Mason when I wrote that! Shocked

There are other new alloys out there as well with Tin-Copper-Silver mixes but I have not tried those as yet since the 62-36-2 mix has served me well.

Phil

No problem Phil. I have to re-edit post 6 times on here just because I am terrible with these membrane keyboards and at age 74, a lot of what I know “aiin’t so 😉”
I used to have problems with the 63-37 I used on circuit boards when soldering tank coils and these silver alloys are considerably stronger and stand more heat, as you have said. 73, Mike
Logged
DMOD
AC0OB - A Place where Thermionic Emitters Rule!
Contributing
Member
*
Offline Offline

Posts: 1663


« Reply #21 on: August 05, 2022, 03:02:37 AM »

...My original point was that those tubes rid themselves of a great amount of heat by simply radiating it away; whether this radiation is in the form of infrared or visible light is irrelevant.
...So, my original question wasn't at all about the longevity of the tubes - those design considerations will be dealt with according to Eimac literature - but rather how big a threat to nearby ancillary hardware - i.e the plate choke sitting in the middle of three glowing 3-500Z's - is that radiation? Maybe none at all, but it seemed a question worth asking.

It is radiation, and is Infrared Radiation from the filament and the plate heating from that source that is impinging on the adjacent choke. It is this radiation that results in a temperature rise of adjacent components.

The choke has a maximum temperature rise spec associated with it under which it can function reliably. There are heat sinks that can be attached to the choke that can help dissipate this heat if you are concerned about that.

I prefer a system that allows air to be sucked up from the cooler lower levels and the hotter air to be exhausted out the top, as in the Apache TX-1 Final cage.

Phil
Logged

Charlie Eppes: Dad would be so happy if we married a doctor.
Don Eppes: Yeah, well, Dad would be happy if I married someone with a pulse.NUMB3RS   Smiley
KD1SH
Member

Offline Offline

Posts: 427



« Reply #22 on: August 05, 2022, 10:45:01 AM »

   Couldn't find any technical specs on the maximum allowable temperature, but it's a pretty robust choke: wound on a 1" OD ceramic form and good for 1.5 Amps. The ceramic form itself is shiny white, so it will tend to reflect a good amount of the radiation. Obviously it was designed for the internal environment of an amplifier, so it should be fine.
   Gets me thinking, though: I suppose that if we were to be extremely fussy, we'd have to de-rate the plate dissipation of each tube ever so slightly when they're operating in close proximity to each other, as opposed to a single tube, since each tube is effectively radiating directly into its partners. In that case, I'd expect that a single 3-1000 could more efficiently dispose of its heat energy than a pair of 3-500's could.
   I must admit that, although I've got a fondness for glass bulbs, blowing air through an external anode tube is probably a more practical way to dispose of waste heat. I still like the glow, though.

...My original point was that those tubes rid themselves of a great amount of heat by simply radiating it away; whether this radiation is in the form of infrared or visible light is irrelevant.
...So, my original question wasn't at all about the longevity of the tubes - those design considerations will be dealt with according to Eimac literature - but rather how big a threat to nearby ancillary hardware - i.e the plate choke sitting in the middle of three glowing 3-500Z's - is that radiation? Maybe none at all, but it seemed a question worth asking.

It is radiation, and is Infrared Radiation from the filament and the plate heating from that source that is impinging on the adjacent choke. It is this radiation that results in a temperature rise of adjacent components.

The choke has a maximum temperature rise spec associated with it under which it can function reliably. There are heat sinks that can be attached to the choke that can help dissipate this heat if you are concerned about that.

I prefer a system that allows air to be sucked up from the cooler lower levels and the hotter air to be exhausted out the top, as in the Apache TX-1 Final cage.

Phil
Logged
DMOD
AC0OB - A Place where Thermionic Emitters Rule!
Contributing
Member
*
Offline Offline

Posts: 1663


« Reply #23 on: August 05, 2022, 03:37:19 PM »

...Couldn't find any technical specs on the maximum allowable temperature, but it's a pretty robust choke: wound on a 1" OD ceramic form and good for 1.5 Amps. The ceramic form itself is shiny white, so it will tend to reflect a good amount of the radiation. Obviously it was designed for the internal environment of an amplifier, so it should be fine...
   

My misinterpretation; I though you were speaking about a power supply choke but this is apparently an RF choke centered between the parasitic choke feeds.

I don't think you'll have any problems with that coke considering its dimensions.

Phil
Logged

Charlie Eppes: Dad would be so happy if we married a doctor.
Don Eppes: Yeah, well, Dad would be happy if I married someone with a pulse.NUMB3RS   Smiley
K9MB
Member

Offline Offline

Posts: 184


« Reply #24 on: August 06, 2022, 11:44:56 AM »

 Respectfully, there's no conflating going on here. All points well taken and appreciated regarding the need to effectively remove heat from the base and anode pins. That's a given, and well documented in Eimac literature. I will be using Eimac SK-410 "air-system" sockets and Eimac SK-406 chimneys, installed per Eimac instructions, and my blower, well, see the picture attached. That blower could probably come close to literally pushing the tubes out of their sockets. I use Magnehelic gauges to read the back-pressure, and the back-pressure could easily be many times what Eimac calls for.
   My original point was that those tubes rid themselves of a great amount of heat by simply radiating it away; whether this radiation is in the form of infrared or visible light is irrelevant. When I'm in my workshop on a cold winter day, I often use a standup quartz heater - purely radiant heat - to keep warm, and that orange glow will heat me and nearby objects to an uncomfortable temperature quite quickly if a respectful distance isn't observed. But, as soon as I turn the heater off, those quartz tubes quickly cool and cease to glow. Some of that heat energy was carried away by air, but the vast majority of it was radiated away as infrared and low frequency visible light. The same thing would happen if my quartz heater was sitting in the vacuum of space with no air to carry away the heat.
   So, my original question wasn't at all about the longevity of the tubes - those design considerations will be dealt with according to Eimac literature - but rather how big a threat to nearby ancillary hardware - i.e the plate choke sitting in the middle of three glowing 3-500Z's - is that radiation? Maybe none at all, but it seemed a question worth asking.
  BTW - the blower is a "bouncy house" blower, exact specs unknown, but if I were sitting on a skateboard and holding this thing, it would send me zooming around my shop. Sounds like fun, actually; if I had more room in my shop I might just plug in a long extension cord and try that Smiley


I am curious what you mean by Silver Solder?
I use two kinds:

1: For outdoor electrical connections and for soldering to amplifier coils and bandswitches, I use an alloy that is 4% silver and 95% Tin. It melts at about 435degrees F compared to 60-40 tin-lead (350degrees) It is also stronger than 60-40 or 63-37.
 2. For attaching 2AWG ground wore to my ground rods, I use a 15% silver alloy that melts at 1450 degrees that is also called silver solder. It is much stronger and pretty weather proof so connections last outside.
Os it one of these you mean? There are a lot of other alloys besides these..

Also, silver solder is not a cure all because improperly,cooled,tube bases can be compromised by the solder in the tube pins melting.
Really, ot is not a question of infrared radiation, but removing heat that is generated.
Infrared radiation is not
I was pretty certain that you did not mean the 1450degree silver solder and that you might be using what I use that is 96% Tin and 4% silver and it melts around 435 degrees instead of 350 degrees for 60-40 tin-lead solder.

I brought it up because of all this talk about infra red radiation when the critical thing is the effective removal of heat to protect the seals and also the pin solder bonds of tubes. Because of the conflation of heat with infrared light, I was not sure that someone might silver solder braze their tube sockets. As imsane as that sounds.

Sorry if I gave you the impression that I thought you used the high temperature. Silver-copper-phosphorus alloy for tube sockets.

I have not used the alloy you mention, but no doubt it is stronger and has a higher melting point than tin-Lead solder. Did you mean 62-36-2 alloy, by the way. That is a common alloy that has 2 percent  silver?


Ok, sounds like you have the solder figured out.
I use a 6% Silver 94% Tin alloy but any silver bearing solder will will work well.

A couple of things. You have enough blower there for several amps.
Have you considered mounting it in a wooden insulated box with baffles and use a 2 inch hose to connect to your chassis
It will be much quieter and still easily supply the 0.08 inch of water head pressure at the sockets.

As far as keeping the RF choke cool, you may consider getting some metalized Mylar film and rolling it into a conical cylinder with the diameter being a bit larger at the bottom and mount it half an inch using small angle brackets above the chassis to allow airflow and you may also drill a few 1/4 inch holes around the choke so that some of the air in the pressurized chassis flows upward from below. Mylar film can handle up to 400 degrees.
Consider making your conical cylinder 2.5 diameter at the bottom and 2 inches at the top. You need only make this shield rise 3 inches above the chassis.
Mylar is an excellent heat insulator and the aluminum coating will reflect I’ve 90% of the radiant heat back. Ideally, more  conicity will reflect the heat more upward toward the top of the camber so if you have space, make the bottom 3 inches diameter.
Logged
Pages: [1] 2   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone © 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.09 seconds with 19 queries.