[BC] Ampex 350

[PeterH]

On Apr 10, 2010, at 12:59 PM, wcj9996 wrote:

> The Ampex 350 had 3 small pins in the hubs that would engage in the  
> slots around
> the center holes in the 3", 5" and 7" plastic reels.  These soon  
> broke off in mt
> experience.  I drilled and taped holes in the Ampex hub for a  
> threded pin that
> would engage all 3 sizes of the small plastic reels.  It was not  
> wise to use
> "long play" tape on the plastic reels with the standard hubs.  We  
> had some 7"
> plastic reels with larger hubs that we used for takeup with the  
> plastic supply
> reels.

IIRC, the 350, and the rather similar 400 and 400A, utilized cast-in  
radial splines.

These were made of the same material as the turntable itself, as  
these were integrally-cast, hence these were Zamac® or a similar zinc- 
aluminum alloy.

The 351 introduced cast-in steel pins, which were almost impervious  
to breakage, unlike the cast-in Zamac splines. In this specific  
respect, the 351's cast-in pins only superficially resembled a true  
spline, but these were ever so much more durable, hence more reliable.

The 440 introduced a revised turntable, in which case an inserted,  
and easily replaceable steel spline system was used. Held in my three  
"button" head machine screws. These splines almost never failed.

There was a field bulletin for the installation of a single  
cylindrical spacer, held in using a 4-40 UNC machine screw, at least  
on the 400 (prior to the introduction of the 400A).

I have perhaps every variation of the above in my shop.

Basically, of you don't "man-handle" your machines, each variation  
should last you a lifetime (well, at least YOUR lifetime).

The cast-in Zamac splines was, perhaps, the ONLY design faux-pas in  
the 350 product.

But, as with about 50-percent of the mechanical details, and perhaps  
100 percent of the electronic details, these were "borrowed" from the  
400A.