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Author Topic: Henry K-2000 amplifier  (Read 20753 times)
HS0ZED
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« Reply #60 on: April 12, 2017, 11:08:50 AM »

I'd say this is quite a rare amp these days. I don't know where how they came up with K-2000 but I'll take a guess the 2000 was its nominal SSB pep input power and the K is very much for Kenwood. This amp was clearly styled as a table top matching amp for the TS-520.

Given the short comings your facing, fear of BeO, fear of tube death, fear of excessive heat etc I would think a better bet is get this amp sorted to be as near standard as possible and then rather than wreck a piece of history with mods move it along to a guy who's into the Kenwood hybrids. I'd think it has sufficient rarity value to return enough for a good single tube glass amp to can hammer away without any fears and mod until it's good with plenty o room in the box. And which no one will likely care if you ain't it pink and add silver streamers to it. Think AL80 et al.

Figure out where you want to be and start from somewhere close. Taking a box that's likely unsuited to the mods you want or need and forcing them upon it seems a recipe ripe for disaster.
 A single or pair of 3-500 tube amp seems to be about where you want to end up but I'm not sure this is the box to start with.
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KM1H
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« Reply #61 on: April 12, 2017, 05:35:11 PM »

I'd say this is quite a rare amp these days. I don't know where how they came up with K-2000 but I'll take a guess the 2000 was its nominal SSB pep input power and the K is very much for Kenwood. This amp was clearly styled as a table top matching amp for the TS-520.

The hybrids are a sure way to destroy those tubes without a lot of care in overdriving during tuning and fairly regular QSY.
That may be why Kenwood decided on the TL-922 instead.
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HS0ZED
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« Reply #62 on: April 12, 2017, 06:34:34 PM »

If it's the one with the roller inductor that would be another potential weak spot.
Were me I'd be scared every time I switched it on something potentially wallet wilting might happen.  Sad

With the abundance of SB200 and 220 amps out there together with all the spares availability, still, it's hard to come up with a significantly different amp in that class that would be more cost effective. At least for maybe the next 5 years or so.
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N0SQ
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« Reply #63 on: April 13, 2017, 08:26:11 AM »

I just got the replacement HV capacitors today. Can anyone explain why these newer capacitors are so much smaller than the originals despite being the same voltage and capacitance? The diameters and screw holes are the same but the length of the original capacitors are 105 mm while the length of the new capacitors are 55 mm!
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AE0Q
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« Reply #64 on: April 13, 2017, 08:40:30 AM »

I just got the replacement HV capacitors today. Can anyone explain why these newer capacitors are so much smaller than the originals despite being the same voltage and capacitance? The diameters and screw holes are the same but the length of the original capacitors are 105 mm while the length of the new capacitors are 55 mm!

Technology advances :-)

Glenn AE0Q
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Glenn and V-NATCH Katie,
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N0SQ
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« Reply #65 on: April 13, 2017, 12:50:24 PM »

Can the silicon grease for cpu fans be adequate to smear the tube to BeO connection? Near as I can tell, the specs are comparable with the recommended stuff on the 8873 datasheet - especially temperature range. I have a full tube of TG-3 doing nothing. I don't know if I've exceeded the shelf life though.
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N0SQ
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« Reply #66 on: April 14, 2017, 07:27:44 AM »

Can the silicon grease for cpu fans be adequate to smear the tube to BeO connection? Near as I can tell, the specs are comparable with the recommended stuff on the 8873 datasheet - especially temperature range. I have a full tube of TG-3 doing nothing. I don't know if I've exceeded the shelf life though.

I guess the Thermaltake TG-7 would be significantly better? It seems that its heat conductivity is significantly better than the Wakefield 120. Do I need to consider other specifications?
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N0SQ
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« Reply #67 on: April 14, 2017, 08:02:28 AM »

I got my new HV capacitors installed last night. Looks like I got the polarity correct since none of them exploded.  Shocked Anyway, it turns out that my HV is 2700 volts as measured by my Fluke 77-4 with an HV probe. The manual was saying that it should be between 2300 and 2500 when SSB is selected. The parts list for the transformer shows that the transformer provides 2200 VAC on the secondary with 220 VAC on the primary winding. So, 2700 volts is about right since the turns ratio (based on 2200/220) is 10.9 and my line voltage is 246 VAC which should give me 2684 volts. I doubt the power company will do anything about the supplied power so should I go shopping for a transformer that can be adjusted up to 250 VAC or go get a line conditioner?   I measured the power supply voltage with the CW/SSB switch in the CW position and got 1886 volts. Since the 8873 tube is in short supply and expensive and that the 3CX400A7/8874 tube seems to be in short supply, I'll run the amplifier with the SSB/CW switch in the CW position. But since the HV is high that means that the filament voltage will be high. I didn't measure the filament voltage but I calculate that it'll be 6.87 volts. I did measure the lamp indicator voltages and they were 13.8 volts when the transformer is rated to provide 12.6 volts with 220 volts on the primary.
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W3RSW
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« Reply #68 on: April 14, 2017, 04:36:09 PM »

Obtain a 10 volt at 10 amp filament transformer and hook it up in the primary of your HV transformer to buck the incoming line voltage down 10 volts.

Nicest if both HV and fil. Are run from same main transformer, then just one bucking transformer is needed outboard, or if everything is powered from one 120 volt plug then only one outboard transformer is needed.
« Last Edit: April 14, 2017, 04:38:45 PM by W3RSW » Logged

Rick, W3RSW
N0SQ
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Posts: 1




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« Reply #69 on: April 14, 2017, 06:33:57 PM »

Obtain a 10 volt at 10 amp filament transformer and hook it up in the primary of your HV transformer to buck the incoming line voltage down 10 volts.

Nicest if both HV and fil. Are run from same main transformer, then just one bucking transformer is needed outboard, or if everything is powered from one 120 volt plug then only one outboard transformer is needed.

I've been trying to find a "plate and filament" transformer to suit my needs but after several hours of websurfing I couldn't find one. Finding one that'll have the same footprint as the existing transformer would probably be another issue.
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KM1H
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« Reply #70 on: April 15, 2017, 06:59:44 AM »


Obtain a 10 volt at 10 amp filament transformer and hook it up in the primary of your HV transformer to buck the incoming line voltage down 10 volts.

Nicest if both HV and fil. Are run from same main transformer, then just one bucking transformer is needed outboard, or if everything is powered from one 120 volt plug then only one outboard transformer is needed.



I've been trying to find a "plate and filament" transformer to suit my needs but after several hours of websurfing I couldn't find one. Finding one that'll have the same footprint as the existing transformer would probably be another issue.

Check the Ameritron AL-572 transformer specs for fit. A bit more HV wont hurt the tubes a bit; just keep the drive and grid current well within the limits.
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N3QE
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« Reply #71 on: April 15, 2017, 08:17:43 AM »

I've been trying to find a "plate and filament" transformer to suit my needs but after several hours of websurfing I couldn't find one. Finding one that'll have the same footprint as the existing transformer would probably be another issue.

I understand you wanting to treat the rare expen$ive tubes in your amp as nicely as possible.

But it still will be a very limited amplifier especially if you're heavy into RTTY. I think it could be a great amp for a guy who only did SSB. I would not be surprised if this would complete someone's "Kenwood collection" with it matching the TS-520 and make them really happy.

Although the tubes are expen$ive they seem to be quite rugged in real-world-use. I know some locals who have owned a SB-230 for 40 years now and the original tubes are still going strong.

If you wanted to protect the tubes, I would look toward grid current trip rather than a power supply overhaul. I don't think you need to drop filament voltage but if you really felt the need, it makes more sense to do it with a resistor or maybe just skinny wire to the filament pins.

I think it makes more sense to invest your money in an amp that better matches your future needs, than to put money into this one. Sure, fix what needs to be fixed to keep it working, but don't view it as an investment.
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N0SQ
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« Reply #72 on: April 15, 2017, 03:12:56 PM »

I've been trying to find a "plate and filament" transformer to suit my needs but after several hours of websurfing I couldn't find one. Finding one that'll have the same footprint as the existing transformer would probably be another issue.

I understand you wanting to treat the rare expen$ive tubes in your amp as nicely as possible.

But it still will be a very limited amplifier especially if you're heavy into RTTY. I think it could be a great amp for a guy who only did SSB. I would not be surprised if this would complete someone's "Kenwood collection" with it matching the TS-520 and make them really happy.

Although the tubes are expen$ive they seem to be quite rugged in real-world-use. I know some locals who have owned a SB-230 for 40 years now and the original tubes are still going strong.

If you wanted to protect the tubes, I would look toward grid current trip rather than a power supply overhaul. I don't think you need to drop filament voltage but if you really felt the need, it makes more sense to do it with a resistor or maybe just skinny wire to the filament pins.

I think it makes more sense to invest your money in an amp that better matches your future needs, than to put money into this one. Sure, fix what needs to be fixed to keep it working, but don't view it as an investment.

I'm going to continue getting this amplifier fixed up. It may not be the best choice for RTTY but it's the cheapest course of action for now. I might use the amplifier for awhile. I'd like to get a solid state amplifier but my experience has been that they're too easily damaged. But, I plan to get a different antenna that doesn't have traps, first.
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N0SQ
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« Reply #73 on: April 16, 2017, 05:34:22 PM »

Turns out that 2 of the input tuning coils have broken slugs. 10 meters and 15 meters. There seems to be something wrong with the 75/80 meter coil also since turning the slug in or out doesn't change the SWR to the rig. The slug is turning so I know the slug isn't broken - maybe the entire coil form needs to be replaced?  I've been looking for replacement slugs but they seem to be non-existant even though the AL-811H that I had owned had input coils with slugs. So, I'm wondering if I could just order the coil forms from Ameritron (or some other vendor) and use them in this amplifier. I would imagine that it would be a close but not exact match. Of course, I could use a antenna tuner between the rig and the amplifier but that wouldn't be as convenient. In case anyone is wondering, the coil forms are 1/4 inch diameter. The 10 meter coil is 5T, 15 meters is 6T, and the 75/80 meter coil is 17T.
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EA3GNS
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« Reply #74 on: March 21, 2019, 08:25:03 AM »

Hello Lee
I own a kenwood k-2000 but i d'ont have a manual.
Can you send me a copy by e-mail?
My e-mail is ea3gns@gmail.com
Thank in advance
David EA3GNS
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