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Re: [Amps] Solid State Amps (or rather the NCL-2000...)

Subject: Re: [Amps] Solid State Amps (or rather the NCL-2000...)
From: Manfred Mornhinweg <>
Date: Sun, 19 Oct 2014 17:17:08 +0000
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There are alternatives Manfred.

Get a pair of 8072's and some defunct 8122's. Machine off the finned radiator and push onto the 8072.

That's a good hint. I had read it before somewhere, but forgotten about it. I have now stored your message in my NCL-2000 folder, for when the tubes fail.

You can do this with other tubes including the 4CX250/300/350 family. Use copper pipe slit to fit to adapt the different sizes.

I have a lathe, so I can actually turn adapter parts if necessary.

Ive even tried the anode cooler from shorted 3-500Z's slipped over the 8072, they actually run quite well to 1200W out since that blower puts out a lot of air

Mine doesn't, because it's a 60Hz blower and here in Chile it has to run on 50Hz, so the airflow is drastically lower. I compensate partially for that by running the tubes at a lower idle current than normal. So far people say that I'm not splattering, so it should be OK.

Convert to the Russian GS-36B or Svetlana relabled 4CX400A. Change to the Svetlana SK2A socket and a new filament xfmr. Other voltages are compatible, even the bias. It also has a much more stable screen that is not prone to current drift. Written up in the 90's by Svetlana and George Baxter, W6TC.

Use a single 3CX800, same socket, minimum reworking. A bit tight in places but done by many.

Get a bit creative and adapt a pair of Eimac 3CX400U7/8961 and use it as a 8874. Real cheap, even NOS as there is no replacement application since all the 800-900 mHz Motorola cell and other cavities have been retired.

When the time comes and the 8122 tubes fail, if that happens before I have my final super top solid state amplifier up and running, then I will consider what to do. Maybe they never fail, because I use that amplifier only rarely. I'm somewhat allergic to noise, and the blower noise is highly irritating to me. Not when I just switch on the amplifier, but after half an hour or so of constant blower noise, I start going up the walls, and shut off the amplifier. That way the tubes last long! ;-)

Several years ago I installed an acoustic labyrinth at the air inlet, and replaced the oil by the thickest grade that would allow it to run. The noise got slightly lower, but not much.

I often think that when the tubes fail, that would be the cue to get rid of the noisy beast!


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