[Boatanchors] Unusual Barker and Williamson (B&W) 370

[GRANT YOUNGMAN]

I seem to have a knack for uncovering undocumented early versions of otherwise standard products.  The last one was a very early TMC GSB-1, which differs in some interesting ways from what is considered the standard GSB-1 as documented in the available manuals.  It also has an interesting mistake on the tuning dial, which may apply to all of the early GSB-1s.

This time it’s a B&W 370 SSB Adapter.  I’ve been looking for one for a while, and finally turned one up in nice shape.  It looks like any other 370 from the outside.  Even a glance at the top of the chassis looks like a 370.  And it’s really well built, too, with a high build quality reminiscent of TMC.  But the one I have does not match the 370 schematic in the commonly available manuals.  It differs in tube layout, the way several internal alignment controls exist or don’t and are laid out, and my early investigation indicates there are quite a few other circuit differences as well.  My hope is that someone out there has a matching manual, or at least a schematic, or at the very least has encountered this 370 version and has some knowledge.  There were minor differences between Run 1 and Run 2 of the “common” 370, but this seems to predate those.  Except for a new cathode bypass cap on the 6V6 audio stage, the circuit is clearly unmolested and original.

The “common” 370 has the following tube layout:

(1) V-1 6SN7
(2) V-2 6SN7
(3) V-3 6SJ7
(4) V-4 6V6
(5) V-5 5Y3

This 370 has the following layout with some different tubes and different nomenclature (listed here in the same sequence as the tubes in the “common” 370:

(1) V-1 6K8
(2) V-3 6A8GT
(3) V-5 6SJ7
(4) V-4 6V6
(5) V-2 5Y3

And the tube types seem to be just the beginning in terms of differences.  For example, the 1N34-based detector in the common 370 is not in this one (I’m assuming Ill discover some other detector configuration once I trace things out).

If anyone has come across such a 370, or has any documentation or knowledge please let me know.  I’m not looking forward to reverse engineering the schematic of this thing, but that may be the only option.

Thanks … Grant NQ5T