[Milsurplus] More on the TCS Filter Adaptor

[Kenneth G. Gordon]

On 31 Jan 2016 at 13:07, David Stinson wrote:

>> Are there any miniature, solder-in tubes that will 
> replace the 6BA6 and 6AU6?

Yes. BTW, I love the submini tubes! Those things are far, far more reliable 
and rugged than previous tubes.

For the 6BA6, you have your choice of several. The most common ones are 
the 5638 and the 5702. 

I can send you an NIB 5702, although you can buy them on eBay for under 
$5 each, or from ESRC in Florida (they have an easily-found web page).

For the 6AU6, you have many more choices. However, the most common is 
the 6540. 

I can send you an NIB one of those, or you can buy them on eBay or from 
ESRC.

ESRC's prices are always far better than those on eBay, BTW.

However, do remember that all of the subminis I know of are limited in max 
plate voltage, usually to 100 VDC or less.

You can find specs for these tube here:

http://pw2.netcom.com/~wa2ise/radios/penciltubes.html

I cannot see how it would be difficult to very easily drop the max plate 
voltage to 100VDC or so within your adapter. A simple voltage-divider using 
resistors would do the job.

That filter adapter you show on your website was fairly common back in the 
day. Collins made them for several receivers including the HRO-50 and 
HRO-60, the SP-600, and some others.

I also have a complete article out of 1957 GE Ham News entitled, "Packaged 
Selectivity" on how to make your own here:

http://www.w7ekb.com/glowbugs/rx/PakSel/PackSel.pdf

This one uses either a pair of 6BA6 tubes or 6BJ6 tubes. The submini 5702 
would work very well here.

vy 73 for now,

Ken W7EKB