On the Emulation of TU58s

Henk Gooijen henk.gooijen at hotmail.com
Tue Jun 16 13:30:02 CDT 2015

-----Oorspronkelijk bericht----- 
From: Johnny Billquist 
Sent: Tuesday, June 16, 2015 8:22 PM 
To: cctalk at classiccmp.org 
Subject: Re: On the Emulation of TU58s 

On 2015-06-16 20:20, Chuck Guzis wrote:
> On 06/16/2015 11:08 AM, Henk Gooijen wrote:
>> The round (approx 2" diameter) "bearings" of the TU80 do not rotate.
>> Instead, the metal has tiny holes. Air pressure pushes the tape away
>> from the bearings. As the tape moves, due to movement pressure, the
>> tape comes closer to the air bearing. That is measured. To get the
>> air pressure back to some sort of equilibrium the pickup or supply
>> reel speed is adjusted.
>> That is how I understand the mechanism ... now writing this down, I
>> think I should read up the Theory of Operation chapter ...
> Pretty much the standard CDC vacuum-column design since the 1960s.  The
> TU80 is, after all, a CDC product.  Two counter-rotating capstans--tape
> movement is determined by applying positive or negative pressure to
> ether or both (i.e. positive pressure on both results in the tape
> "floating"

Uh... The TU80/TU81 do not have vacuum columns...


well, the tiny space between the tape and the air bearing could
be regarded a vacuum column, but it's a very short one :-)
The two air bearings are immediately above and below the R/W
and erase head. And they do *not* rotate. The tape glides on
an air cushion over the bearing.

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