[Amps] Drake L4 tube replacement

[Will Matney]

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