[ARC5] BC-230/420 4-pin VT-25/52 to 7/9 pin mini update

[Ben Hall]

Good morning all,

Update - progress has been slowed due to some family medical issues that 
have been the focus of most of my attention.  :(

On the good news side...in addition to the 9-pin to 4-pin adapter 
prototype, I'm close to having a 7-pin to 4-pin adapter prototype made. 
  It will look just like the 9-pin, except it will have a 7-pin 
miniature socket.

Tube socket availability appears to be a minor problem.  I bought some 
new-manufacture (read:  Chinese) 9-pin "ceramic" tube sockets off the 
e-place.  They are unsuitable, as the metal mounting ring is not firmly 
attached to the socket.  In addition...one of the five I bought is 
defective.  (one could probably epoxy the ring to the ceramic, but I'd 
worry about thermal cycling and difference in coefficient of thermal 
expansion to eventually break the epoxy joint)

I also bought both some NOS and some new-manufacture 7-pin sockets off 
of the e-place.  These are reasonable quality and should work well.

I did notice one issue I'm not happy with.  The pins in these miniature 
sockets all have some degree of what I'll call "float."  I assume this 
allows for tube pin misalignment.  Depending on the socket, an inserted 
tube will have some "wiggle."  One some of the sockets I just bought, it 
is perceptible, but probably acceptable.  On the removed from equipment 
sockets that I have that were designed to be used with shields, it's 
totally unacceptable.  I may see if I can find some high-temp silicone 
o-rings that will go around the tube at the junction of the tube and the 
socket to try and minimize this wiggle on the better tube sockets that 
have the least wiggle.

I do plan to place an order with our friends at Antique Electronic 
Supply to see how nice (or not nice!) their non-ceramic micalex sockets 
really are.

Anyways...I'm still working on these.  My goal is to get a small run of 
prototypes put together in a week or so to see how they work in service.

thanks much,
ben