6EW6

[Kenneth G. Gordon]

On 8 Jul 2009 at 17:44, Paul Kraemer wrote:

> Heath group
> Does anyone else have as poor luck as I seem to with the 6EW6 used
> many places in Heath gear?

Yes. I had one in an SB-401 that had a really weird internal short that 
took me several weeks to track down as the symptoms it caused were 
so strange.

> Is there an upgrade to this tube? Paul K0UYA

I kind of doubt it....at least not without rewiring the socket. 

The 6EW6 exhibits unusually high transconductance of 14000 
micromhos for one thing.

According to NJ7P's tube database, the 6GM6 is the preferred 
substitute, and the following tubes can also be used as substitutes:

6BJ6, 6BZ6, 6CB6, 6CF6, 6DE6, 6DK6, 6JH6, 6HQ6.

However, I doubt if any of these last have the high transconductance 
that the 6EW6 has.

The 6GM6 has 13K micromhos transconductance, but it is a semi-
remote cutoff type, while the 6EW6 is a sharp-cutoff type.

The 6JK6 appears to be a good candidate, but would need testing in our 
circuits, and the 6JL6 might work also. Their transconductance is higher 
than the 6EW6.

In the SB-401, the two 6EW6s are used as mixers. The high 
transconductance ensures good mixer efficiency with relatively low 
noise. 

Ken Gordon W7EKB

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