HP 7970E - interest to split?
elson at pico-systems.com
Sat Sep 30 12:04:21 CDT 2017
On 09/30/2017 06:58 AM, Tony Duell via cctalk wrote:
> One of my tape drives has a set of equal-value resistors connected to
> each of the read channels, the others ends of the resistors being brought
> out to a testpoint. You connect a 'scope there and read a skewmaster
> tape. The idea is that if the read transitions all occur at the same time
> (no skew) you get a pefect step on the 'scope, if some are later than
> others you get a staircase. You adjust the heads for the smallest
> width of the stairs.
Yes, this is the classic NRZI skew adjust testpoint. The
resistors sum up the read data latches, that are set by
seeing a transition of either polarity on a data channel,
and reset by a one-shot that is set to about half a
You run a skew tape or a tape written with all ones. If you
see a square wave, all is good. If you see a slope on the
wave, adjust the skew adjust screws on the head mount to
make it as straight as possible.
More information about the cctech