On 2/25/2024 10:52 AM, Jim VE7RF wrote:

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'.

It's kinda hard to fit a 3x3 into a desktop cabinet.

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

... with a high 3-digit, maybe low 4-digit electric bill...

On Sat, Feb 24, 2024 at 11:40 PM, Steve wrote:

>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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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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I've been offered this job lot from a SK sale...

I recognise 3CX15k, 4CX5k, Gu81m, ITL9-1, BR1106, Vac-Vars (10-200, 25kV) any idea's for the rest?

There are some kanji characters on the big glass bulbs, so Japanese maybe

?

Like Steve said, Digi Key is the only way to order them. The original in my amp was a Magnelab. They are poorly built and according to Glenn, all of the Magnelab transformers have failed. Alpha was replacing them as late as 2009 under warranty, if I recall what he told me correctly.?

Anyway, my 99 is good to go and I am loving busting pileups again.? :)

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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.?

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Kinda hard to fit a 3CX3000-anything into a 7-inch-high desktop cabinet, even without anything connected to the top or bottom? 8-)

How do you match them up...even if they are good ?? ? ?2 tubes are bad enough....and 3 of em is a pita.?

I ran into this same problem eons ago on hb amps.? 2 x really good tubes...when tested one at a time...... but when used in pairs, the current does not split 50-50.? Some were 60-40, and some were 65-35.? ?I have pairs of 4-400A/B/C's? and the pairs of 4-400A's and also? the pair 4-400B's? match up good, with a 50-50 split.? However the pair of 4-400C's don't match up, even though when tested one at a time, put out rated power.?

After that, it was just a single tube for any hb amp.? Need more PO, use the next bigger tube that is available.? ?IE: 3x3, 3x6, 3x10, 3x20.? ?Or 4x5, 4x10, 4x15.? ?Pick just one of either triode or tetrode.?

Nobody puts more than one engine in a pickup truck.? Get a bigger engine.?

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.?

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Don't nobody be intending to call and talk to Tim on the phone over the weekend; he'll have his ears plugged with wads of paper in anticipation of those bangs? 8-D

"?They will work for B+ applications, but have to be-derated for voltage." .... that's the question, right there.

If it's rated 8kV, will it cope with 6,500V?? Because if it doesn't , 800J is going to make a big bang :-(? ? ? We will find out over the weekend.

According to PSUD2, simply using the 38uF will fix the ripple problem without using the choke too.

"?They will work for B+ applications, but have to be-derated for voltage." .... that's the question, right there.

If it's rated 8kV, will it cope with 6,500V?? Because if it doesn't , 800J is going to make a big bang :-(? ? ? We will find out over the weekend.

According to PSUD2, simply using the 38uF will fix the ripple problem without using the choke too.

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If you are using more than one tube, you are using the wrong tube!

How do you match them up...even if they are good ?? ? ?2 tubes are bad enough....and 3 of em is a pita.?

I ran into this same problem eons ago on hb amps.? 2 x really good tubes...when tested one at a time...... but when used in pairs, the current does not split 50-50.? Some were 60-40, and some were 65-35.? ?I have pairs of 4-400A/B/C's? and the pairs of 4-400A's and also? the pair 4-400B's? match up good, with a 50-50 split.? However the pair of 4-400C's don't match up, even though when tested one at a time, put out rated power.?

After that, it was just a single tube for any hb amp.? Need more PO, use the next bigger tube that is available.? ?IE: 3x3, 3x6, 3x10, 3x20.? ?Or 4x5, 4x10, 4x15.? ?Pick just one of either triode or tetrode.?

Nobody puts more than one engine in a pickup truck.? Get a bigger engine.?

On 2/21/2024 7:42 PM, Jim VE7RF wrote:

Why did u have to go through digikey..and not directly with hammond /
dahl ?

I tried ordering my replacment 2K4A XFMR from Dahl/Hammond, and they
told me I had to order it through DigiKey because DK was now their
distributor; so I did. Initially, there was some confusion; the DK
person on email (I cannot hear on a phone, so have to use either text or
email) didn't think there was such a model as what I wanted. I asked her
to check with Dahl/Hammond, who had told me to order from DK; I gave her
the name of the person I'd corresponded with at Dahl/Hammond. She did,
then I got an order-confirming e-mail after a few days asking for my DK
account schtuff. Once I gave that, it was another few days until I got
an ack from DK they had received that info. THEN I waited TWO WEEKS with
no ack they had accepted my order; so I emailed again, they said they'd
check... and finally, a couple days later, I received an e-mail
acknowledging my complete order... and listing a delivery time some
FOUR-PLUS months down the road. I initially emailed Dahl/Hammond in late
January, DK finally sent this email around the middle of March. The
delivery was scheduled, by FEDEX Fright, for the middle of July, IIRC.
As it happened, this all occurred just prior to, and then during, the
first few months of CV-19.

I was finally alerted by FEDEX around the end of June that my XFMR would
be available for pickup locally in a couple weeks, then in a week got
another e-mail it would be on time when they said.

After FEDEX emailed me that last time, they emailed me again several
times, trying to claim my XFMR had been sitting there waiting for me for
a week, and they would return it as "Unclaimed"... as it happened, on
the SAME date they had originally said it would be available for pickup.
I had to have my brother get on the phone with them and he finally got
through to them I was WAITING for the delivery date.

... And then finally, I drove there (turned out to be just a couple
miles away from where I lived at the time), the forklift brought it out,
and I had to cut it loose from the pallet and get it out of the wooden
box, both of which may have weighed almost as much as the XFMR. The
parking lot had a lot of pallets that customers had cut their goods
loose from.

It all was an adventure I don't want to repeat.

Steve, K0XP

Why did u have to go through digikey..and not directly with hammond / dahl ?? ??

NO hv sag at all, that's superb.?

IMO, whatever the B+ is? with amp keyed, and sucking normal idle current is the real no load B+.? ?It has to idle 1st, before you ac apply drive.? ?I really could care less what it is in RX.? ?But that has it's limitations.? Like if EBS is used, etc.?

Alpha? 91 / 99? xfmr's are failing? ?at a high rate these days.? ?Same deal with the older ACOM amplifiers.? The issue is, they have a total of 5 windings on the secondary side..... and in all the failed units, the high voltage winding, is arcing to a lower voltage winding.? ?The insulation has broken down over the years.?

Dahl never went cheap with the insulation..and neither did Hammond.? I still have hammond plate xfmrs made in the late 50's that still function, even with floating CT's....and also stuffing 247 vac into the 210 vac pri.?