> From: Johnny Billquist
> One more thing to check this summer...
OK, if you can, that would really be great; if either i) it's still together,
or ii) there are pictures, it would fill some of the key knowledge gaps.
In particular, i) what kind of backplane is it plugged into, and ii) what is
the UNIBUS edge connector on the card connected to...
Noel
I was looking at a couple of documents describing the Pertec tape interface; the manual for my Kennedy 9610 tape drive, and a nice reference by a fellow with a rather familiar name:
http://www.sydex.com/pertec.html
According to my Kennedy manual, issuing a read command causes the drive to return one block of data. I can see how that would be used in block-oriented applications in which blocks may be randomly read, written and re-written on the tape. But most of my magtape experience has been using the tapes in a streaming mode, such as when reading/writing one or more tar archives separated by file marks.
When writing a tar archive on a magtape from a Unix system, is the archive written as a sequence of fixed-size blocks? Or is the entire tar archive effectively written as one continuous block which must be streamed with no repositioning?
I'm curious because I'm daydreaming about how to build a tape drive interface controller, and I wonder whether it might need to potentially stream an entire tape in one go vs. being able to safely assume some maximal block size.
--
Mark J. Blair, NF6X <nf6x at nf6x.net>
http://www.nf6x.net/
I don't know how many of you were familiar with the
Addressograph-Multigraph (AM) Varityper phototypesetting systems.
Basically small computers with floppy drives and a (very nice)
terminal--and a big box that held quite a number of photo "font" disks.
Basically worked by shining a light through a specific disk and
character onto light-sensitive paper. Produced gorgeous print ready
copy. Compugraphic and Mergenthaler had similar systems and I think
there were also several other competitors as well.
At any rate, a pile of 8" HS floppies will be landing here in the near
future. Does anyone have any leads on Varityper service manuals or
anything might help me with the task of figuring out what on the disks?
(The disks themselves do not come from a country that uses the Latin
alphabet).
Thanks for any leads...
--Chuck
-------------------------------------------------------------
"The first thing we do, let's kill all the spammers."
A few weeks ago, while I was testing a spare IPB-80 CPU card in an
Intel Series II MDS, the monitor stopped working, with the raster
collapsing to a very bright dot in the center of the screen. I hit the
power switch and pulled the line plug immediately, but the dot
persisted for several minutes, only gradually dimming.
I just started investigating it. With the monitor cable unplugged from
the IOC board, the +15V DC at the IOC connector reads 0.74V. Of the
two DC power supplies described in the service manual, this MDS uses
the Power One. The +15V rail uses a separate transformer winding, a
723C regulator, a house-marked (12500-4) NPN pass transistor, and a
zener and SCR crowbar. The 0.74V makes me think the crowbar has
tripped and the 723 regulator is current limiting. Nothing else in the
MDS uses the +15V supply.
I was a bit lucky that this particular MDS used "method A" of
installing the monitor, which makes it easier to remove. Once the
metal shield is removed, the label was visible. It is a Ball
Electronic Displays TV-120 monitor, which is a common enough model
that it was easy to find the service manual online. I'll test the
monitor on a lab power supply to see if it's drawing too much current.
I may kludge up Rich Ottosen's PIC-based TV test pattern generator on
a breadboard.
Some people seem to think that "reforming" an aluminum electrolytic
capacitor is some kind of cheat, akin to zapping NiCd cells or
rejuvenating CRTs. Actually reforming is the same electrochemical
process that the manufacturer uses to "form" the capacitor in the
first place, building up the aluminum oxide layer, before the sheet is
rolled into cylindrical form. The manufacturer typically uses a
forming voltage higher than the rated voltage, from 135% to 200%, to
provide margin for shelf life.
When the capacitor goes unused for an extended time (shelf life), the
oxide layer gradually breaks down, increasing the capacitor's leakage
current and reducing the effective usable voltage of the capacitor,
which is proportional to the minimum oxide thickness. If the oxide has
developed spots that are too thin for the applied voltage, it may be
damaged ("punch-through") when that voltage is applied. Punch-through
tends to be a runaway process, so even a small amount of punch-through
usually completely ruins the capacitor. Reforming the capacitor by
applying current-limited power rebuilds the oxide layer to prevent
this type of damage, and to reduce the leakage current back to within
the specifications. The current limiting is what prevents the
reformation process from causing punch-through and damaging the
capacitor. Many of the capacitor vendors actually publish
recommendations for reforming their capacitors.
See for example information on manufacture on pages 13-14 and a brief
recommendation of reforming procedure on page of 17 of Kemet
publication F3304 dated June 2009:
http://www.kemet.com/ProductCatalog%20Documents/F3304.pdf
Also pages 2-4 on manufacture and page 16 on "recondition" (reform) of
"CDE Aluminum Electrolytic Capacitor Application Guide":
http://www.cde.com/resources/catalogs/AEappGUIDE.pdf
Also pages 1-5 of Nichicon "General Description of Aluminum
Electrolytic Capacitors":
http://www.nichicon.co.jp/english/products/pdf/aluminum.pdf
In at least some aluminum electrolytic capacitor manufacturing
processes, there is actually a reforming step done after assembly, in
addition to the initial forming. See page 9 of the Panasonic
"Aluminum Electrolytic Capacitors Technical Guide", dated April 2013:
http://industrial.panasonic.com/lecs/jp/i/29880/TAL_E/TAL_E.pdf
The reforming process WILL NOT fix other things that may go wrong with
the capacitor, such as failed seals allowing the electrolyte to dry
out, or corrosion, or punch through which can result if the oxide
layer is degraded and voltage is applied without current-limiting.
The US DoD published a technical handbook detailing their policies and
procedures for reforming aluminum electrolytic capacitors that sit in
inventory for years, MIL-HDBK-1131. As of 1999 this is "for guidance
only and should not be cited as a requirement, but the information in
the handbook may be useful in determining or evaluating requirements."
For non-mil-spec capacitors, it recommends inspection and possible
reformation every 3-6 years of shelf storage. It recommends disposal
after 12 years of shelf storage, but AFAICT they're just being
conservative, possibly due in part to not having enough practical
experience with reforming very old capacitors.
Shelf storage is of course equivalent to having the capacitor
in-circuit but unpowered. Having the capacitor powered in circuit for
any significant length of time will reform the oxide to some extent
based on the applied voltage, though not up to original factory spec.
When I reform capacitors myself, I use a reforming voltage of 135% of
the rated voltage. Since I use a suitably low current limit, this has
no significant probability of damaging the capacitor, but as with the
initial factory forming, provides some margin for further shelf life.
In my experience, aluminum electrolytic capacitors in equipment that
has been unpowered for 30 years or more almost always need
reformation, but they almost always meet factory specs (capacitance,
ESR, and leakage at rated voltage) after reformation. Since I don't
tend to restore equipment newer than that, I don't have any empirical
data on how much shelf life they can have without needing reformation.
I'm not particularly advocating for or against reformation, as
compared to replacement. Anyone restoring equipment with electrolytic
capacitors is advised to to read the references and decide for
themselves.
Eric
I remember the Research Machines 380Z and wouldn't mind getting one should
the opportunity arise. But I have no recollection of a "Special Control
Unit", so does anyone know what this is?
http://www.ebay.co.uk/itm/Faulty-Vintage-Research-Machines-380Z-Special-Cont
rol-Unit-Computer-/331617471655?
Some kind of peripheral maybe?
Regards
Rob
Still cleaning the shop, trying to be out by the end of the week-ish. We have the following
equipment available:
TU-80 family tape drive, in frame. Works, passes diagnostics. Make offer. Photos:
http://microfilmks.com/LMSI/
Unknown power supply module. Has NCR part numbers but google gives no love. +5 (x2), -5, +12, -12.
Make offer. Photos: http://microfilmks.com/Ebay/UnknownPSU1.jpg and UnknownPSU2.jpg
Discom electron tube, PN 123788-2. These came out of COM microfiche cameras, and have a blue
display. Not sure how to go about shipping them securely, but if you're interested, we can figure
it out. I have several of these.
DEC SHD1Z-ZZ SCSI drive cabinet, tower configuration. Has SCSI-2 personality module, power supply,
SCSI terminator and cable, 6 drive trays for 50-pin drives. Also has 4 spare drive trays and one
spare power supply. Includes 6 1.2G SCSI drives, or if you prefer, I can remove them to lower the
shipping weight. Asking $50 obo.
All shipping is from Wichita, Ks, 67213
--Shaun
drlegendre wrote:
----
How did his last missive make it through to the list in the first place?
Didn't Jay just recently say he was perma-banned?
----
Within moments after I posted that he was banned, I went to the mailman interface, and his account was not in the membership list. I assumed he had unsubscribed himself shortly after his first post.
When I saw his next (and last post), I dug further. His email was on a "whitelist" along with all members of cctech. This was a vestige of how the old "two lists joined at the hip" was configured. So I had to manually remove him from the whitelist, even though he wasn't subscribed. My Apologies for the oversight, but I believe it is fixed now.
Be advised that there is always a chance he's still subscribed under some other unknown/non-descript email address. I'll weed them out as they are discovered.
J
On 7/30/15 6:55 PM, Jay West wrote:
> You wrote....
>> I really dont see the reasoning behind my classiccmp ban, You just banned me for no reason..
> You are incorrect. Just because you don't understand the reason doesn't mean I banned you for no reason. I will not be dragged into a senseless passive-aggressive exchange about it.
>
>> Because of you I cant even come out to VCFMW with my 10 year old son..
> You are also incorrect on this point. I did not mention VCFMW at all. I banned you from classiccmp, not VCFMW.
>
>> You know how much thats going to hurt him that he doesn't get to show off his project that he worked so hard to program on his Apple II. Thats going to destroy him.. So I hope you are happy.
>> Thanks for the fun times.. Hope this makes you sleep well at night knowing you destroyed a 10 year olds excitement.
> Statements like the above are a good portion of the reason why you were banned. I did not destroy a 10 year-olds excitement. You did that all on your own, through your own actions.
>
> J
>
>
>
>
>
Jay
Seriously go fuck yourself.. That is all. You are a Jackass.
If i showed up to VCF Id promptly knock you on your ass, you and
mos6581 both. Hence why Im not coming, you bitch boys arent worth
sitting in a chicago jail over.. So go enjoy your dope smoking circle
jerk and FUCK YOU
Stopped in the local electronics haunt, and the owner directed me to a "Fine
to Very Good" IBM 5150. I did not look at it closely, but externally appears
to be very good shape with minor scratches on the under-side. It has two FH
5.25's, and a cassette port on back. He did say that "memory had been
expanded". No monitor, keyboard, or mouse. He's asking $75.00.
If someone has a serious interest, I'd be happy to go look at details on it.
The owner is a friend and he'd certainly let me open it up if need be. I'd
also be willing to pack/ship for the excruciating cost of. "A promise of a
future beer" :)
Best,
J
