test-drb July 2015

test-drb@ccmp.vtda.org

176 participants
257 discussions

by jnc＠mercury.lcs.mit.edu

> 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

8 years, 8 months

Pertec Tape Drive Interface Musings

by nf6x＠nf6x.net

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/

8 years, 8 months

AM Varityper (phototypesetter)

by cclist＠sydex.com

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."

8 years, 8 months

diagnosing an Intel Series II MDS monitor failure

by spacewar＠gmail.com

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.

8 years, 8 months

Reforming capacitors (technical description, not politics)

by spacewar＠gmail.com

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

8 years, 8 months

RM 380Z Special Control Unit (?)

by robert.jarratt＠ntlworld.com

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

8 years, 8 months

Equipment available (Wichita, Ks)

by microfilm＠microfilm.kscoxmail.com

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

8 years, 8 months

accidental post allowance

by jwest＠classiccmp.org

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

8 years, 8 months

A Final Word (FINAL)

by slandon110＠gmail.com

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

8 years, 8 months

IBM 5150 available ($)

by jwest＠classiccmp.org

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

8 years, 8 months

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test-drb July 2015