On 2005-06-26 09:21:36 -0400, Charles MacDonald said:

Malcolm Fuller wrote:

But a deviation in pin size? C'mon. As I pointed out in my earlier
posting, the octal based tube was first used in 1935. How many millions
of octal based tubes been made since then? And, as I asked before, why
would a tube firm, like JJ, go through the motions of making what could
be a great tube only to get the most elemental, and least technical,
part of the tube, it's pins, wrong? The pin diameter of an octal tube
has absolutely nothing to do with the internals of a tube; the leads
coming out of the glass envelope are soldered to the ends of the pins
that are a part of the Bakelite base. Pins of an octal are not reliant
on tube design, but are reliant on a separate base design - a design
that has been around for 70 years. To get that wrong is careless.

Of course, this assumes that JJ chose the wrong pin size on purpose,
which is not known, and moreover, it's not known that I had a bad
batch. This is why I started this thread originally, to find out
what's really that answer. It wasn't to malign JJ, or to bad mouth
tubes of which I only have, at most, 90 seconds of experience with.

In the fifties and later - Octal pins DID get smaller, and tapered. GE
refers to this in the literature for TV repair folks - Their "service
designed" line had tapered pins to make the job of changing tubes more
convenient.

Folks that used 6SN7s in NON-ATT Phone systems complained, and had
special batches made with non-tapered pins.

Get out a micrometer and see if the pins are significantly smaller than
on a GE "service designed" 12SN7GTA...

That maybe so. But the 7591 would've been developed after this overall
change. This also tells me another thing of significance, and that was
that people were allowed to complain and those complaints were heard
and satisfied. Why is it that when people have legitimate complaints in
this day and age their told to stop whining? In the thread, I was
essentially told that Sovtek and JJ made their 7591s not for vintage
amp owners such as I,, but for hobbyists, or companies, to build amps
around them. If that were true, why did they designate the tube as a
7591. They know where the market is. It's funny to me to see that
people would rather come up with excuses why a company had to get a
product wrong rather than demanding they get it right. We live in a
consumer driven world, but we're giving up all our power. That's not
right.

But getting back to the pins. GE was known for doing other funky things
with octal bases; in the 70's they developed the "coin based" octal. I
do not have a micrometer, nor do I have a "service designed" 12SN7GTA.
However, I do have a quad of "coin based" 7591s and they fit my sockets
just as snugly as the OEM tubes. Can I assume that these coin based
pins have the size and taper size you did describe?

Thank you for your response.

Malcolm