On Tue, 16 Mar 1999 08:01:08 -0800 Vic Rosenthal <rakefet@rakefet.com>
writes:
>
>Peter Chadwick wrote:
>>
>> Especially if you're only looking for 1500watts of CW, why not
>4CX250B's? 4
>> of them, 2kV at an amp or so, and you're there. You should be able
>to pick
>> them up reasonably cheaply with sockets. Over here, I'd reckon to
>get
>> sockets and 4 tubes for under $150.
>
>I thought about this. My investigations so far haven't lead me to any
>cheap
>ones. They may be out there, but the prices I've seen so far have
>been quite
>high. Unfortunately, I can't ask for a guarantee on flea-market tubes
>for an
>amp that I haven't built yet, so I need to get them from a reliable
>source.
>
>> Do you really need instant on?
>
>I can live without it. It's just one point in favor of filament-type
>tubes. Of
>course, the other side of the coin is that the filament current is
>higher,
>requiring a big transformer and filament choke.
>
>> The big advantage of 3-500Zs to my mind is that the blower
>requirements are
>> such that it's likely to be reasonably quiet.
>
>My SB1000 uses a muffin fan to cool the tube and seems quite noisy. I
>would
>like the one I'm building to be quieter.
QRO seldom is quiet Vic. Of course you can run a YC-156 and a muffin fan
at QRP levels!
The brand new SB-220 fan assy from Harbach is very quiet.
73 Carl KM1H
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