[Ace Rimmer]

I’ve seen this in a few places. Some say they are medical grade tubes.
What (if any) advantage do medical grade tubes have over the garden variety?





P.S.
Book and schematic for MacKit30
http://65.29.159.126:20102/MacKIT30sm.pdf
http://65.29.159.126:20102/MacKIT_30_schematic.pdf

[robert casey]

Ace Rimmer wrote:

I’ve seen this in a few places. Some say they are medical grade tubes.

Is the red tip embedded into the glass of the envelope, or just painted
on regular tubes that presumably passed tighter quality control? If
embedded, that would imply that the factory had to do it. If painted
on, then anyone could do that to any old tube....

[GregS]

In article et, robert casey wrote:
Ace Rimmer wrote:

I’ve seen this in a few places. Some say they are medical grade tubes.

Is the red tip embedded into the glass of the envelope, or just painted
on regular tubes that presumably passed tighter quality control? If
embedded, that would imply that the factory had to do it. If painted
on, then anyone could do that to any old tube....

These are painted tops. They represent matching qualities for differential amps.
There were at least three colors. The Grass Instrument company did the painting
for the Grass stripchart plugins. I had or have a description somewhere from a fellow
involved in testing these tubes. Regardless, they can command large
prices on Ebay. I have found most of the pulls from the equipment show large variations
in the gain between sections so the testing may not be valid after many hours of use.
They are still high quality, long lasting, low noise tubes.

greg

[Ned Carlson]

GregS wrote:

The Grass Instrument company did the painting
for the Grass stripchart plugins. I had or have a description somewhere from a fellow
involved in testing these tubes. Regardless, they can command large
prices on Ebay.

That's silly, unless they're in Grass packaging and positively unused.

I have found most of the pulls from the equipment show large variations
in the gain between sections so the testing may not be valid after many hours of use.

The different sections may have had much different usage, so the
difference in wear between sections in pullouts should be
expected.


They are still high quality, long lasting, low noise tubes.

So are any Telefunken 12AX7's or 12AU6's. Grass may have graded
them, but grading doesn't improve the tube itself, it merely
means that the least obstinate failures have been culled
out. Did Grass claim that the factory handpicked or specially
built 12AX7's for them?

--
Ned Carlson
SW side of Chicago, USA
www.tubezone.net