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Author Topic: Henry K-2000 amplifier  (Read 19657 times)
N0SQ
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Posts: 1




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« Reply #45 on: April 10, 2017, 01:45:59 PM »

Can the silicon grease be wiped off of the BeO block? Considering how deadly the dust can be, it seems like that's a bad idea. Leave it to industry, BeO is safe unless you mess with it - just like asbestos. I'm going to get rid of the heatsink+BeO block first chance I get. If the BeO block isn't permanently attached to the heatsink, I'll dispose of just the block. But, who will take the BeO off my hands?
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W9IQ
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« Reply #46 on: April 10, 2017, 03:25:08 PM »

Once BeO is fired into a solid (ceramic) form, it is not harmful waste under Federal regulations. You can dispose of it in a landfill. Avoid machining or abrating it as it is the dust (particulates) that is the carcinogenic form of BeO.

- Glenn W9IQ
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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
N0SQ
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« Reply #47 on: April 10, 2017, 04:08:31 PM »

I don't know what happened since a couple of days ago but it looks like the availability of the 8874/3CX400A7 is much less and the cost is higher. One place was selling the tube at over $2000. Most places were selling the tube between $450 and $850. I sure hope I don't lose my 8873's anytime soon.
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N0SQ
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« Reply #48 on: April 10, 2017, 04:17:19 PM »

It's kind of interesting that my amplifier doesn't show up at http://www.henryradio.com/oldamplifiers.html.
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N3QE
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Posts: 5561




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« Reply #49 on: April 11, 2017, 03:57:19 AM »

I don't know what happened since a couple of days ago but it looks like the availability of the 8874/3CX400A7 is much less and the cost is higher. One place was selling the tube at over $2000. Most places were selling the tube between $450 and $850. I sure hope I don't lose my 8873's anytime soon.

It would require a screen supply, but two 4CX250B's would be a step up in dissipation from what you currently have in there.

4CX250B filament voltage/current is very similar to 8873. A dropping resistor, or just some skinny wires, will get you to the right place.

Unless you have infinite amounts of free time, I don't think it makes any sense to retrofit air-cooled tubes into your current chassis. If/when your 8873's die, I think your amp becomes a source of parts for your next amp.
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W3RSW
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« Reply #50 on: April 11, 2017, 04:52:14 AM »

2k Ultra shows up as a pair of 887'3s in your list. '72 thru '76.
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Rick, W3RSW
W1QJ
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« Reply #51 on: April 11, 2017, 04:58:05 AM »

The amp is listed as a Tempo amp.
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N3QE
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« Reply #52 on: April 11, 2017, 05:57:31 AM »

2k Ultra shows up as a pair of 887'3s in your list. '72 thru '76.

Henry 2K Ultra does also use two 8873's, but in a very different tall and skinny box:



vs the K-2000 which obviously has TS-520 styling and low profile form factor:



And do not confuse with the Henry Tempo 2000 which was also low profile form factor and I think used 3-400 glass tubes:

« Last Edit: April 11, 2017, 06:07:44 AM by N3QE » Logged
N0SQ
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Posts: 1




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« Reply #53 on: April 11, 2017, 06:07:10 AM »

2k Ultra shows up as a pair of 887'3s in your list. '72 thru '76.

The image of the amplifier in that manual doesn't match what I have so it can't be the same amplifier.
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N0SQ
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Posts: 1




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« Reply #54 on: April 11, 2017, 06:11:29 AM »

2k Ultra shows up as a pair of 887'3s in your list. '72 thru '76.

Henry 2K Ultra does also use two 8873's, but in a very different tall and skinny box:



vs the K-2000 which obviously has TS-520 styling and low profile form factor:



And do not confuse with the Henry Tempo 2000 which was also low profile form factor and I think used 3-400 glass tubes:



The second image looks like my ampifier.
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N0SQ
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Posts: 1




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« Reply #55 on: April 11, 2017, 08:22:43 AM »


vs the K-2000 which obviously has TS-520 styling and low profile form factor:




It's interesting that oldtuberadio.com lists it as a KENWOOD product. I don't see Kenwood marked on this amplifier anywhere. The manufacturer name on the serial number plate says Henry K-2000. Anyway, there doesn't seem to be much info on this amplifier on the web. Good thing I got a manual with this radio (which has a few errors in it, though). Must not have been a big seller?
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N0SQ
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Posts: 1




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« Reply #56 on: April 11, 2017, 08:30:23 AM »

I don't know what happened since a couple of days ago but it looks like the availability of the 8874/3CX400A7 is much less and the cost is higher. One place was selling the tube at over $2000. Most places were selling the tube between $450 and $850. I sure hope I don't lose my 8873's anytime soon.

It would require a screen supply, but two 4CX250B's would be a step up in dissipation from what you currently have in there.

4CX250B filament voltage/current is very similar to 8873. A dropping resistor, or just some skinny wires, will get you to the right place.

Unless you have infinite amounts of free time, I don't think it makes any sense to retrofit air-cooled tubes into your current chassis. If/when your 8873's die, I think your amp becomes a source of parts for your next amp.

I can't say that I have infinite time but I am retired.
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KM1H
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Posts: 4722




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« Reply #57 on: April 11, 2017, 09:40:48 AM »

Quote
And do not confuse with the Henry Tempo 2000 which was also low profile form factor and I think used 3-400 glass tubes:

The Tempo 2000 was designed by Johnson as the Thunderbolt II but they decided to exit the ham market and sold the product with tooling, etc to Henry.
They are rather scarce but I have worked on a couple...a bit of a PITA also Roll Eyes

Back in the 80's when full power 8874 pulls were cheap at $50 or so I machined off the fins on a side and silver soldered a thick copper plate to mate to the BeO block.
With an external muffin fan on the heat sink and another on the cover with the silicon chimney I already mentioned everything ran quite cool and a couple of customers have told me they are still running that amp decades later with the same tube.

Carl
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N0SQ
Member

Posts: 1




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« Reply #58 on: April 11, 2017, 11:15:24 AM »

I don't know what happened since a couple of days ago but it looks like the availability of the 8874/3CX400A7 is much less and the cost is higher. One place was selling the tube at over $2000. Most places were selling the tube between $450 and $850. I sure hope I don't lose my 8873's anytime soon.

It would require a screen supply, but two 4CX250B's would be a step up in dissipation from what you currently have in there.

4CX250B filament voltage/current is very similar to 8873. A dropping resistor, or just some skinny wires, will get you to the right place.

Unless you have infinite amounts of free time, I don't think it makes any sense to retrofit air-cooled tubes into your current chassis. If/when your 8873's die, I think your amp becomes a source of parts for your next amp.

I might just try to extend the life of the amplifier if the 8873's do die even though this amplifier doesn't cover 160 meters or the WARC bands. I have been looking into the possibility of using the 3-500Z tubes even though they uses a lower filament voltage. The 3-500Z tubes are cheaper also. Hmm, I wonder if some web-bot is seeing what we're considering doing and are causing tube prices to go up. At any rate, it'll be fun to "tinker" with this amplifier. Is it possible to convert this amplifier to air cooled with the 8873's?
« Last Edit: April 11, 2017, 11:17:47 AM by N0SQ » Logged
KM1H
Member

Posts: 4722




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« Reply #59 on: April 11, 2017, 06:09:06 PM »

Quote
It would require a screen supply, but two 4CX250B's would be a step up in dissipation from what you currently have in there.

4CX250B filament voltage/current is very similar to 8873. A dropping resistor, or just some skinny wires, will get you to the right place.

And the end result would sound like a CB amp or an ALS 500 as far as IMD. They are a late 40's design before SSB became popular. They are the bane of 6 and 2M around the world as well as HF.

OTOH a pair of cathode driven 8904/4CX350FJ's or a single 4CX600J or JA would equal some of the best that triodes could do. The 350 shows often on Fleabay and the 600's less often but if youre not in any rush think about it.

The Russian GS-36B/4CX400A is an excellent tube with one of the available
Tetrode regulated screen & bias kits from GM3SEK, etc.

Carl
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