Steve nobody puts a 3x3 or any other big tube into a desktop unit.? ?They all go into a standard 19"/ 24" rack.? Typ the blower hangs below the bottom of the chassis.? ?Putting a 100 lb box on a desk is nuts.?

My racks all sit in the shop next door.... 4 in total...all in a row.??

But the real question is why would you want a noisy pa in the same
room with you.

Agreed,? Don't start any amp project, unless you have at LEAST TWO
known good tubes.? ? And don't build any amp with more than one
tube....pita.? ?You will have a helluva time trying to play...'match up'.

As a bonus, you can heat the home in winter, with...'free heat'.

>Regardless, with just one unknown-condition example of either, you'd be foolhardy to design anything around one...

>Steve, K0XP

Agreed,? Don't start any amp project, unless you have at LEAST TWO known good tubes.? ? And don't build any amp with more than one tube....pita.? ?You will have a helluva time trying to play...'match up'.??

That 3x15 triode with the flex leads is the H3 version.? ?Those are low mu...and useless? for cathode driven / GG amplifier service.? ?However, it can be rebuilt? by econco, and they will replace the grid with a high mu grid. It's done all the time.? Then it becomes the ultimate tube, since no socket required.? ?Just bolt the grid flange to the chassis.? Apply 1.5 kw of drive....and blast away with 30 kw pep out.? As a bonus, you can heat the home in winter, with...'free heat'.

?

We have the fil choke for those 160 amp and lower down to a fine art.? It's just a simple matter of sliding a mess of fair-rite type 43 oval beads over a pair of 1-0 power cables....done..... in abt 20 secs flat.?

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Regardless, with just one unknown-condition example of either, you'd be foolhardy to design anything around one...

Steve, K0XP

Strange. On the link you sent on one photo it shows the 6T51 as a glass tube but on another photo it shows it as an external anode. Even on evilbay they show a 6T51 as an external anode as a FU-605.

?

Mod-U-Lator,

Mike(y)/W3SLK

?

?

?

From: [email protected] [mailto:[email protected]] On Behalf Of Tim Fern
Sent: Saturday, February 24, 2024 4:19 PM
To: [email protected]
Subject: Re: [ham-amplifiers] Identifying some rare tubes...

?

Indeed, but sadly the only other pictures I have:



Looks like this? (reading backwards through the glass) is a 6T51?



Designed as an industrial heater oscillator triode.? Not sure it would be much use for anyone here?

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Atr 50Hz 1.2A will be permitted when winding a transformer with that wire.

At free air 14A will be maximum.

?

73

Peter, DJ7WW

?

?

?

-----Original-Nachricht-----

Betreff: Re: [ham-amplifiers] Ameritron Plate Chokes

Datum: 2024-02-22T17:36:36+0100

Von: "Jim VE7RF" <jim.thom@...>

?

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Oopsie... I didn't notice earlier that you mentioned the 8K's choke is wound on teflon...

Steve, K0XP

Yup; PTFE's a pretty good thermal insulator at low temperatures (i.e.: below its melting or burning point), especially compared to ceramic. Moreover, the ceramic can take a couple thousand degrees before it'll suddenly fail (likely by shattering); not so with that PTFE rod.

Also, consider just how long you're letting that current heat up the wire and ceramic rod; it'll take more current when cold compared to after it's been warmed up.

A glazed ceramic rod would probly suck up more heat since its surface is smooth and thus makes good thermal contact with the wire, compared to the unglazed ceramic rod. I would expect that if you ran the same thermal runaway test using an equivalent glazed ceramic rod, it would probly allow higher current (and thus higher temperature), but then once the rubicon is crossed, it might also show a faster thermal runaway characteristic. If the 8K's choke is wound on a glazed ceramic rod, that's likely why it takes off so quickly. Or perhaps its wire isn't making as good contact to the coil form.

It's all Thermodynamics? 8-)

Steve, K0XP

On 2/22/2024 8:36 AM, Jim VE7RF wrote:

While on a roll, I tested both my Ameritron plate chokes.... by hooking em up to my small 0-36 vdc @ 3 amp CCS lab supply.?
They will take 1.5 amps CCS, and run at room ambient temp for hrs.? ?They get warm with 1.7 amps....and don't really get hot till 1.9 amps.??
I was using current limit mode.? When they start to get pretty warm, their DC resistance increases a bunch, and the lab supply? Vdc slowly starts to increase to compensate...and maintain the desired current.? ?At that point, it's just I squared x R.... and the choke goes into thermal runaway.? ?

What baffles me is the 180 uh large choke, used in the 8K ultra also runs at room temp, with 1.5 amps CCS.? Any higher than that, and it heats up incredibly fast.? It will burn ur fingers with 1.8 amps.?

Scott's theory is the 1" diameter, solid? Un-glazed ceramic used on the Ameritron choke may well be absorbing any heat.? ?Whereas the 1" solid Teflon rod used on the Henry choke is the ultimate heat insulator.?

The magnet wire used on the 8K appears to be bigger than what's used on the Ameritron, like by at least 2 gauges.??

?

Years ago, I ran a test, by stuffing 5 amps CCS, through a 3' length of 22 ga magnet wire, laying on the carpet, in a big circle....with the ends directly into my 0-60 vdc @ 5 amp? CCS lab supply.? Stone cold after 1 hr.? So no clue at the time exactly how much 22 ga magnet wire will handle in free air.?

While using the same 5 amp lab supply to test the recently acquired 4H, 127 lb Dahl choke, something was amiss, and for whatever reason,? I quickly disconnected? one of the 18 ga test leads to the choke (with I think 5 amps flowing through it), and the back EMF took out the 5 amp lab supply, white smoke billowing out of it.? ?Those lab supplies have every protection there is...except for back emf.? The fix is? to install a RVS connected diode across the output of the lab supply.? Dunno why they didn't install one internally.?

Ok, bought another 0-60 vdc supply, but this time a 10 amp CCS unit. (they also made a 15 amp unit).? Dragged it out the other day....and ran the same test, through another 4' piece of 22 ga magnet wire, also in a loop, with 3/4 of it in mid air, and hardly any of it touching the carpet.? I measured the OD of the magnet wire, and it's .028".? It's 22 ga all right.? (.028" OD on the enamel).? Started at 5 amps CCS for 20 mins, then increased the current.? Stone cold at 7 amps. Started to warm up at 9 amps, and I could definitely feel the heat with supply maxed out at 11 amps CCS.? That was an eye opener.?

That's open air. Wind a plate choke with it, and the max CCS DC current rating drops like a rock.?

--
See my QRZ.com page at

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Yup; PTFE's a pretty good thermal insulator at low temperatures (i.e.: below its melting or burning point), especially compared to ceramic. Moreover, the ceramic can take a couple thousand degrees before it'll suddenly fail (likely by shattering); not so with that PTFE rod.

Also, consider just how long you're letting that current heat up the wire and ceramic rod; it'll take more current when cold compared to after it's been warmed up.

A glazed ceramic rod would probly suck up more heat since its surface is smooth and thus makes good thermal contact with the wire, compared to the unglazed ceramic rod. I would expect that if you ran the same thermal runaway test using an equivalent glazed ceramic rod, it would probly allow higher current (and thus higher temperature), but then once the rubicon is crossed, it might also show a faster thermal runaway characteristic. If the 8K's choke is wound on a glazed ceramic rod, that's likely why it takes off so quickly. Or perhaps its wire isn't making as good contact to the coil form.

It's all Thermodynamics? 8-)

Steve, K0XP

While on a roll, I tested both my Ameritron plate chokes.... by hooking em up to my small 0-36 vdc @ 3 amp CCS lab supply.?
They will take 1.5 amps CCS, and run at room ambient temp for hrs.? ?They get warm with 1.7 amps....and don't really get hot till 1.9 amps.??
I was using current limit mode.? When they start to get pretty warm, their DC resistance increases a bunch, and the lab supply? Vdc slowly starts to increase to compensate...and maintain the desired current.? ?At that point, it's just I squared x R.... and the choke goes into thermal runaway.? ?

What baffles me is the 180 uh large choke, used in the 8K ultra also runs at room temp, with 1.5 amps CCS.? Any higher than that, and it heats up incredibly fast.? It will burn ur fingers with 1.8 amps.?

Scott's theory is the 1" diameter, solid? Un-glazed ceramic used on the Ameritron choke may well be absorbing any heat.? ?Whereas the 1" solid Teflon rod used on the Henry choke is the ultimate heat insulator.?

The magnet wire used on the 8K appears to be bigger than what's used on the Ameritron, like by at least 2 gauges.??

?

Years ago, I ran a test, by stuffing 5 amps CCS, through a 3' length of 22 ga magnet wire, laying on the carpet, in a big circle....with the ends directly into my 0-60 vdc @ 5 amp? CCS lab supply.? Stone cold after 1 hr.? So no clue at the time exactly how much 22 ga magnet wire will handle in free air.?

While using the same 5 amp lab supply to test the recently acquired 4H, 127 lb Dahl choke, something was amiss, and for whatever reason,? I quickly disconnected? one of the 18 ga test leads to the choke (with I think 5 amps flowing through it), and the back EMF took out the 5 amp lab supply, white smoke billowing out of it.? ?Those lab supplies have every protection there is...except for back emf.? The fix is? to install a RVS connected diode across the output of the lab supply.? Dunno why they didn't install one internally.?

Ok, bought another 0-60 vdc supply, but this time a 10 amp CCS unit. (they also made a 15 amp unit).? Dragged it out the other day....and ran the same test, through another 4' piece of 22 ga magnet wire, also in a loop, with 3/4 of it in mid air, and hardly any of it touching the carpet.? I measured the OD of the magnet wire, and it's .028".? It's 22 ga all right.? (.028" OD on the enamel).? Started at 5 amps CCS for 20 mins, then increased the current.? Stone cold at 7 amps. Started to warm up at 9 amps, and I could definitely feel the heat with supply maxed out at 11 amps CCS.? That was an eye opener.?

That's open air. Wind a plate choke with it, and the max CCS DC current rating drops like a rock.?