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Re: [Amps] Drake L4 tube replacement

To: "amps@contesting.com" <amps@contesting.com>
Subject: Re: [Amps] Drake L4 tube replacement
From: Will Matney <craxd1@ezwv.com>
Date: Sat, 16 Oct 2004 15:27:13 -0400
List-post: <mailto:amps@contesting.com>
Jason Buchanan wrote:

Jan Erik Holm wrote:

Yes! Just like when you run out of gas in your
car, just put new in.



Well, the consensus is that I need to find new chimneys to use the 3-500Z on account of the 3-400Z is a shorter tube.


There appear to be 3 different chimneys - SK 406 (4.75" tall), SK 406A (4.25" tall) and SK 406B (4" tall). Sounds like the 3-500Z chimney in use with the L-4B would be the 4.75" SK 406 chimney - the question becomes whether the 4.75" chimney will fit in the older L-4.


For fit always measure from the base of the tube, to the top of the anode connector to check if the tube will fit withing the chassis height. The 3-500ZG is used in the Drakes (L4 & L4B) as a replacement, so I know they will fit. The chimney is shorter than the maximum height of the tube, its mouth comes just below the anode connector. The chimney is a SK406 which is the 4.75" high one. If I recall, all of the 406 versions are the same diameter, so it will fit the old clips. The 3-500Z's maximum height is 5.2" high. This from the base of the glass to the top of the anode cap. Seems to me that the L4B chassis height was either 5-1/2" or 6" deep. It's been so long I can't remember for sure. Anyhow, I don't think you'll have any problems.

I haven't seen any 3-400Z tubes for sale anywhere so it seems that the 3-500ZG types that are available today are the only option for replacement, and they require the tall 4.75" chimney. "Cooling" is good so I don't want to skimp just to get by with the wrong sized chimney.

Ron W2CQM has piqued my interest with the 8877 retrofit but my uncle and grandfather would tar and feather me for hacking this L-4 - this amp part of the family!! hi hi


73 Jason N1SU


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Will Matney
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