30 Oct
2005
30 Oct
'05
5:01 p.m.
Unfortunately the read/write IC (1820-2418) on the
HP-85 can only deal with
one head at a time (only one DIO pin), so to employ the one-pass strategy,
you either have to wire another 1820-2418 strapped to read track two, or you
have do the analog (audio) recording I suggested initially.
The latter is probably easier.
They DO use the same tape so they must be
compatible. I don't know about
the track spacing but I would think they would be the same.
Bad news. I checked the specs (TechData brochures from hpmuseum.net)
and came up with this table for read/write speeds
HP 9825 22ips
HP 9835 22ips
HP 9845 22ips (didn't find any data, but I assume its 22 ips)
HP 85 11ips
HP 9815 10ips
So there goes any hope of cassette data interchange between the Series80
and the rest of the HP line. :-( My advice is to go for 9915As I have seen them go for
next to nothing on eBay,
and even then remain unsold. Apparently people do not realize that these are
Series 80, or they are discouraged by the lack of screen and (most importantly)
keyboard!
The monitor is trivial, of course. And the keyboard shouldn't be a
problem now that the matrix layout (same as an 85) and connector pinout
are available.
PS I found another metric screw up:
In the 9835TechData-5953-0982-12pages-Oct78.pdf file in hpmuseum.net
the length of the tape is given as 426.7 METERS, followed by the
Presumably 42.67m
more reasonable 140ft (the HP-85B spec sheet gives the
length of tape
as 43m or 140ft).
-tony