More SB-200 issues

[Kenneth G. Gordon]

On 6 Jul 2009 at 9:08, Wb2fou at aol.com wrote:

> I get all my tubes from Antique Electronics Supply . They have a 30 
> day warranty. Never had a problem.

I have bought many tubes from them and agree with you. I have never had a 
problem either.

However, for the 572B, their price is $152.00 EACH even when they are "on 
sale" like they are now. And those tubes are NOS, being at least 20 years 
old.

For that price, I can buy 4 of the Shuguang tubes in matched sets of two. If 
one out of those 4 is bad, that still leaves me with three good ones for the 
price of one from AES.

And if my experience with my "new" Cetron is any indication, I would have 
been sending at least one back to AES if I had bought from them.

On another note, I got a message from Mike Hardie VE7MMH who 
suggested that the problem I had with the tube with the off-center press was 
mainly due to the fact that in the SB-200 (and other amps like them) the 
tubes are mounted horizontally, and that the tubes were probably tested 
mounted vertically. It it had been mounted vertically, it never would have 
failed.

I agree with him, as I have never liked mounting tubes horizontally, although 
many manufacturers do it and have done so for many years. The Collins 30L-
1 comes to mind as I believe the 811s in that amp are mounted horizontally. 
RCA in its tube manuals always mentions whether or not a tube can be 
mounted horizontally or not, and how that should be done. 

Even so, I don't like doing that. It makes sense to me that if there is any sort 
of imperfection in the tube, it would be exacerbated by mounting it 
horizontally.

Ken Gordon W7EKB

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