>
>Subject: how sloppy are speed tolerences in QIC drives
> From: compoobah at valleyimplants.com
> Date: Sat, 12 Nov 2005 13:36:17 -0600
> To: <cctalk at classiccmp.org>
>
>I'm trying the vinyl tubing approach in replacing the drive roller, since it sounds like it would be difficult to slide in a different QIC drive when I need to use tape (no one suggested tips on that). How "sloppy" can the drive roller dimensions be? is there a feedback loop for speed regulation that interfaces directly to the tape, or does it rely soley on the stepper motor and parts dimensions? I think I'm about 1/32" too large, but it could be bigger, since it's hard to measure goo, not more than 1/8th, though.=0D=0A=0D=0A
Well, the TU58 servos off the motor and I found it tolerent of at least 1/16"
variation.
If the drive servos of the data then tolerences are far greater.
Allison
>One thing I forgot to mention in my last message. Get a good continuity
>tester. 'Good' means one that is not fooled by diode junctions (and
>preferably not by low-ish resistors), one that doesn't supply enough
>voltage or current to damage anyting, one that beeps, and one that beeps
>quickly (you want to be able to 'stroke' a probe along a line of pins to
>see if a given connection goes to any of them).
A useful trick I sometimes use when I have trouble following a connection
(especially those which "disappear" into a multi-layer board). If you just
can't figure out where a signal goes - cut squares of tinfoil, and press
them against sections of the board with a firm sponge (something with
enough give to let the foil seat against all the pins). Then using a good
continuity tester such as Tony describes, you can quickly cover large
areas to quickly narrow down where exactly a signal is located. (use foil
squares sized as needed).
Obviosuly you do not want the board powered at all - insure that caps are
discharged, batteries removed etc.
Regards,
Dave
--
dave04a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com Collector of vintage computing equipment:
http://www.parse.com/~ddunfield/museum/index.html
While reading an old resume, I came across something I forgot about. I
used to admin some 3Com 3+ and 3+/Open systems. 3Com made the hardware
(beefed up PC stuff) and wrote or owned the OS.
Anybody know what became of 3+/Open?
-James
James Fogg
JD Fogg Technology Consulting
18 Watershed Lane
Wilmot, NH 03287
(603) 724-2243
www.jdfogg.com
Hey does anyone know where I can buy 3 prong Molex connectors, particularly
those used to connect a QBUS box to a DEC power bus, and the one that goes
>from a cable to the power bus connector? I can't find them anywhere on
Molex or AMP's web site.
>I have a book called "Build your own Z-80 computer" by Steve Ciarcia.
>Is this the sort of thing that would have some interest in an
e-version?
I'm sure Mr Ciarcia would be interested if this were put on line, but
not
in a good way.
>Is there a fast way to scan bound materials without butchering them?
It is MUCH less expensive to find a second sacrificial copy of the types
of bound documents that classiccmp-ers would be interested in than the
cost of something like a Kurzweil book scanner. The Mustek Opticbook USB
scanner is OK for book scanning, but is isn't particularly fast.
Hi !
Could anyone give me the REAL pin assignment of the terminator used on the
IBM 5110 / 5120 systems ?
Has anyone build such a terminator ?
I tried to build one and I'm fed up with getting always the same error : I
can obtain the file list (using basic command UTIL DIR,D80 or UTIL DIR,D40)
but 5 seconds after giving me the file list, the systems blocks, the promt
disappeared and I must restard all... No led is lightning on the
pannel...Sometimes I get the 24 or 26 error code (''diskette error...''is
only said in my reference manual : what a help !).
Very strange diagnostic...
Thanks for your help ;-)
Fred.
I'm trying the vinyl tubing approach in replacing the drive roller, since it sounds like it would be difficult to slide in a different QIC drive when I need to use tape (no one suggested tips on that). How "sloppy" can the drive roller dimensions be? is there a feedback loop for speed regulation that interfaces directly to the tape, or does it rely soley on the stepper motor and parts dimensions? I think I'm about 1/32" too large, but it could be bigger, since it's hard to measure goo, not more than 1/8th, though.
Two-leaded passives are easy to get with a soldering iron and a pair of curved-nose hemostats (check with
friends in the medical profession- those and dental tools (picks, explorers) are really convienient to have- if
you're extremely lucky you'll find someone who's getting rid of a unit- they have air/water syringes (great for
blowing out small stuff) and high-speed air turbine "dremel" type things- tres useful).
Just clamp the hemostat to one lead, touch a small soldering iron to the back, pull, same with other lead.
They're cheap new, but sometimes I don't want to go out to get them. SMTs are a bit harder, but I've done them, too.
