David Knepper wrote:
Todd, you have to be very careful when removing those 75TH tubes, which were
the original types used in the 30K-1.
Uh huh, *now* ya tell me. Actually I broke it a few years back when
simply trying to remove it so I could restore the mod deck. It made me
wanna puke when I realized what just happened, so I stuffed it back into
the chassis and shut the door for a while. Finally found a pair of
replacements back in May.
What you need are adapters that slip over the grid pins. These were made by
Eimac to be used with any of these tubes that had that pin arrangement.
These caps slipped over the pins and were much more sturdy than the grid
pins.
Well, that was the problem: these caps are some kinda weird, they split
down the center and are held together under pressure on the pin not by
ONE snap ring on top, but also by another beneath it. I'd never seen
them before so I was trying to get the tube out to where I could eyeball
it better. Those snap rings require goofy pliers to remove them, and
it's not the type of thing for the faint of heart to attempt by reaching
under the cap with a mm or less of clearence between the cap and the top
of the glass envelope.
Today I did the smart thing. After removing the tubes last night with
plate caps and wires still attached (I removed them at the ceramic posts
on the chassis), off we went to see my friend Ray, KC1BT who is a former
BC engineer and has seen, made, and repaired at least one of everything.
He'd never seen this type of cap before either, but his pliers are a lot
better than mine so we prevailed. It was actually easier to slide the
cap off the intact tube with only the top snap clip removed since the
envelope held the pin in place firmly (unlike the one I broke).
So...now they're sitting in the radio room, waiting to be installed
later tonight. The next step is obtain a crystal for 40M AM and
hopefully to locate the plug in inductor cans for the oscillator and
multiplier plate circuits in the 75M band. The mod 5 differs from the
ham version in that it has two switchable crystal controlled frequencies
with complete tank circuits which each require a combination of 4 coils.
My rig came set up for 6-8 Mcs and 2 - 3.4. Would be nice to find a
complete coil set along with a 310C-2 vfo unit. I traded for a 310B-2,
only to find out it was the wrong unit for my transmitter. Maybe someday
we can work on 40?
73, Todd KA1KAQ
