Re: 3-phase power
On Tue, Jan 4, 2022 at 8:36 PM Grant Taylor via cctalk < cctalk@classiccmp.org> wrote: > My limited understanding is that VFDs simulate / emulate various > frequencies by turning the output on and off (at full input voltage) > such that the (sliding) /average/ of the output looks like it's a at a > lower voltage. That's how all buck switching power supplies work. It's just a question of how much low-pass filtering you do on the output. A switching power supply to power sensitive electronics that requires good voltage regulation and low ripple contains electrolytic capacitors on the output. A VFD may or may not. The specs on the VFD should tell you about the output characteristics. If you're just going to power a three-phase synchronous motor, then no filtering is needed. The inductance of the motor windings and the mechanical characteristics of the motor will filter it just fine.
Re: cctalk Digest, Vol 88, Issue 2
I mean if you want to add a transformer to it you can do anything to want with voltages. It doesn't provide you 120V from the service transformer. Corner grounded Delta gives you a grounded 3 phase service (safer than ungrounded) with one less wire than high-leg delta (3 instead of 4), making it cheaper when the wiring was the expensive part. Patrick Finnegan On Tue, Jan 4, 2022, 22:16 Grant Taylor via cctalk wrote: > On 1/4/22 7:43 PM, Patrick Finnegan via cctalk wrote: > > It's the even more obscure corner-grounded delta, which requires even > > more care and can't provide 120V power, since the phase to ground > > voltage is 240V. > > Why couldn't 120V be derived from either of the 240V phase and the > grounded corner via a 2:1 transformer? > > I'm not sure how to get the two opposing 120 legs, or if they are > strictly required in this instance. I would wonder if it would be > possible to ground the center tap on the secondary side of the 2:1 > transformer mentioned above or not. > > > > -- > Grant. . . . > unix || die >
Re: cctalk Digest, Vol 88, Issue 2
> Why couldn't 120V be derived from either of the 240V phase and the > grounded corner via a 2:1 transformer? It can. That's often how, say, an Edison base decorative luminary is run when all other lighting is 277V (the ratios would of course be different). Otherwise someone invariably screws a 120V bulb into a socket providing 277V. > I would wonder if it would be > possible to ground the center tap on the secondary side of the 2:1 > transformer mentioned above or not. Sure, that's one way of getting split phase 120/240V on a delta system. You've basically made high leg delta the hard way. You do also get to use a completely separate two busbar panel for your 120/240V loads, which prevents the "oops that empty breaker spots give 208V to ground" mistake. A more common method of supplying significant small loads on a delta service is to use a delta:wye transformer and provide 120/208Y. This provides more even loading on the three-phase service, and also provides 120/208Y for, say, computers :P The center/star connection in the secondary is grounded at the transformer. Thanks, Jonathan
Re: 3-phase power
On 1/4/22 11:04 AM, Paul Koning via cctalk wrote: I've said that too, and I've been told that this is not a good idea for power supplies. Something about the waveforms involved in VFDs. My limited understanding is that VFDs simulate / emulate various frequencies by turning the output on and off (at full input voltage) such that the (sliding) /average/ of the output looks like it's a at a lower voltage. So when you're early in the typical sine wave (first 45°) the output is on a small percent of the time and off a large percent of the time. Near the upper portion of the peak (45°-135°) the output is on a large percent of the time and off a small percent of the time. Repeat that method on through the sine wave. So, you end up with very odd shaped signal. Supposedly motors (or any inductive load) can smooth the pulsations to behave more like a true sine wave of the simulated / emulated frequency. Non inductive loads don't smooth / average things nearly as well. Hence why you probably want to not use a VFD to power computer equipment. At least that's my understanding. The other option, typically somewhat more expensive but cheaper than an 11/780, is a rotary converter. Those are 3 phase motors, sometimes modified a bit, driven from single phase power that construct the missing phase somewhat like a dynamotor would. Wouldn't that be construct the /two/ missing phases? You input one phase between the two lines and get the other two phases between the two existing lines and the added line. Those things produce proper sine waves so they are good to use even with things that are picky. Yep. -- Grant. . . . unix || die
Re: cctalk Digest, Vol 88, Issue 2
On 1/4/22 7:43 PM, Patrick Finnegan via cctalk wrote: It's the even more obscure corner-grounded delta, which requires even more care and can't provide 120V power, since the phase to ground voltage is 240V. Why couldn't 120V be derived from either of the 240V phase and the grounded corner via a 2:1 transformer? I'm not sure how to get the two opposing 120 legs, or if they are strictly required in this instance. I would wonder if it would be possible to ground the center tap on the secondary side of the 2:1 transformer mentioned above or not. -- Grant. . . . unix || die
Re: cctalk Digest, Vol 88, Issue 2
> For what it's worth, the building I bought has two services installed when > it was built in 1921 - single phase 120/240 for lighting loads, and 240V > Delta for three phase loads. I bet you have a fun electrical system :D > It's the even more obscure corner-grounded delta I love the reaction when a tech or plant electrician encounters corner-grounded delta for the first time. The meter says one phase is missing, yet everything is fine! Often coming off a backfed transformer turning 208Y into 480 delta, which also apparently blows some minds. I did once see what happens when a new guy connects the neutral on the Y primary side. Thanks, Jonathan
Re: cctalk Digest, Vol 88, Issue 2
On Tue, Jan 4, 2022, 18:15 Jonathan Chapman via cctalk < cctalk@classiccmp.org> wrote: > > High-leg delta exists so you can have 120/240 lighting and appliance loads > in a building that consumes mostly 3-phase, like a machine shop with an > office. In most areas you aren't allowed to have more than one type of > service to a building (not sure if that's true for double-fed sites, never > seen one with two kinds though). I've heard the Power Company usually > doesn't want to install high-leg delta anymore for a variety of reasons: > the load limit, people not understanding they need to skip a breaker, > 120/208Y having become the usual form of smaller service three phase, etc. For what it's worth, the building I bought has two services installed when it was built in 1921 - single phase 120/240 for lighting loads, and 240V Delta for three phase loads. It's the even more obscure corner-grounded delta, which requires even more care and can't provide 120V power, since the phase to ground voltage is 240V. Patrick Finnegan
Re: 3phase power for VAXen [was Re: VAX 780 on eBay]
On Tue, Jan 4, 2022 at 5:17 PM Rich Alderson via cctalk < cctalk@classiccmp.org> wrote: > > We did not have a 3phase outlet on the second floor of the building where > the > collection was housed, and there was no room for the first VAX in the small > computer room on the third floor, so Ian and Keith came up with an > alternative: > They tested all the outlets on the second floor and determined that there > were > three within reach of the room in which Ian was going to work on the 785 > which > were fed from 3 different phases off the big honking breaker panel (200A > service, IIRC). Keith put together a box with the appropriate NEMA socket > and > three heavy duty cords feeding into it, which in turn were plugged into > three > outlets on the walls around what eventually became the vintage exhibition > hall > at Living Computers: Museum + Labs (the eventual name of the place after > the > modern exhibit space on the first floor was built). > > So it's possible to power a 780 or 785 without a power supply rebuild if > you > simply have the right (industrial) breaker panel in your building... > > Happy New Year, everybody! > > Rich > After looking at the 869-D diagrams and the 11/780 power diagram, this makes sense. The power diagrams show 3 120VAC circuits. There is no phase relationship required between the phases, EXCEPT in the 869-D itself. The 4 pole 30A circuit breaker will trip if any (L1, L2, L3, N) is overloaded. If L1, L2, L3 are out of phase then the neutral doesn't carry much current, but if they are all the same phase then the total limit will be 30A. There are 4 connections L1, L2, L3 and N. In the US you would connect the highest current draw leg to one side of the 120VAC and connect the other two legs to the other 120VAC phase and then HOPE that it works. The 869-D outlet are: unswitched L1 switched L1 switched L2 switched L3 For me, if I can buy a Shelby Cobra, I buy it first and figure out where to park it later. Chuck D.
Re: 3-phase power; was: cctalk Digest, Vol 88, Issue 2
> On Jan 4, 2022, at 7:08 PM, Jonathan Chapman via cctalk > wrote: > >> much of it related to Niagara Falls and other power systems >> modeled after it. > > The IIRC oldest US generating station still in operation (on original > hardware anyway) is at Mechanicville, NY. It is hydroelectric and originally > fed 40 Hz AC to Schenectady. They just sped up the alternators when they > connect it to the 60 Hz grid! > > I hear the European equivalent of US 25 Hz traction power is 16.6 Hz. That's one of the choices. When I was in high school, I saw an ad in a technical (engineering) magazine for an electric train, a "four system" one that could run anywhere in western Europe. It could handle 1500 V DC (used in Holland), 3 kV DC, 15 kV AC I think 50 Hz, and 30 kV AC 16.67 Hz -- or maybe the frequencies were the other way around. An electric system that can handle a 20:1 ratio of voltage inputs, and probably several megawatts, in a mobile device is rather impressive. Especially in the 1960s. paul
Re: 3-phase power; was: cctalk Digest, Vol 88, Issue 2
On 1/4/22 4:04 PM, Grant Taylor via cctalk wrote: > I knew about 50 and 60 Hz and DC growing up. I learned about 400 (?) Hz > being used in military applications about a decade ago. 25 Hz was a > surprise to me over the last year or so. I read some interesting > things, much of it related to Niagara Falls and other power systems > modeled after it. 400Hz of course, could be encountered if one shopped war-surplus airborne electronics. I still remember adventures on Chicago's S. Michigan "Surplus Row". Word was that the original plant acquired a generator from a bankrupt carnival operator in the 1910's. But it was used all over the place; my job was with the pyrometer (instrumentation) department. It was incredible seeing the lengths that were taken to avoid using 60Hz power for things like a chart recorder. It was explained that the 25Hz power was generated on-site from coke oven gas and so was essentially free, while the 60Hz was purchased from the local utility. DC, of course, was used for overhead cranes and welding. Every shop had outlets with yellow labels indicating the voltage and frequency. You could plug a coffeepot or hot plate into the 110V (not 120 or 115 or 117) 25Hz outlet, but beware of using it for much of anything else, save lighting. BTW, you have seen no more irritating lighting than mercury-vapor lamps running off of 25Hz. Even in our shop, which used 220V 25Hz incandescent lighting, you could see the pulsation. I did discover that you could take a 110V 25Hz induction motor fan and plug it into 230V 60Hz for a real kick in performance...and probably shorter bearing life. 440V/460V 3-phase in both frequencies were in most shops. Said plant has long since vanished. This was the day of blast furnaces, open hearth furnaces and all the stuff that it fed, like merchant mills, hot- and cold-rolled sheet, tinplate, galvanized...all from a bunch of rocks. --Chuck
Re: 3-phase power; was: cctalk Digest, Vol 88, Issue 2
> The IIRC oldest US generating station still in operation (on original > hardware anyway) is at Mechanicville, NY. Well that ruined my evening, Wikipedia says the generating station now uses the power to mine bitcoins, because it's more profitable than selling it to the public grid. Thanks, Jonathan
Re: 3-phase power; was: cctalk Digest, Vol 88, Issue 2
> much of it related to Niagara Falls and other power systems > modeled after it. The IIRC oldest US generating station still in operation (on original hardware anyway) is at Mechanicville, NY. It is hydroelectric and originally fed 40 Hz AC to Schenectady. They just sped up the alternators when they connect it to the 60 Hz grid! I hear the European equivalent of US 25 Hz traction power is 16.6 Hz. Thanks, Jonathan
Re: 3-phase power; was: cctalk Digest, Vol 88, Issue 2
On 1/4/22 4:46 PM, Chuck Guzis via cctalk wrote: In fact, in my neighborhood, each house has a big green disconnect box on the street fed by 3-phase 11KV. Every so often, the utility sends out a notice that they'll be "re-balancing" the distribution. I imagine that that involves nothing more than changing one phase wire in the big green box. I'm used to 1-4 houses being on a common transformer where I grew up. They were usually installed on polls / pads at the corner of one of the properties on the back property line and feed the four touching properties. He advised that I should put some distance between the transformer and myself, as it wasn't unusual for these things to turn into pyrotechnic displays. Ya. I've seen some spectacular videos. The higher the voltage, the more spectacular. When I worked in heavy industry, it was eye-opening to see the range of voltages, phasings and *frequencies* entailed in the operation (we had 25 Hz, 60 Hz and DC). And, of course, the mistakes made by the electricians in installing various equipment. I knew about 50 and 60 Hz and DC growing up. I learned about 400 (?) Hz being used in military applications about a decade ago. 25 Hz was a surprise to me over the last year or so. I read some interesting things, much of it related to Niagara Falls and other power systems modeled after it. Voltages around the world through the last century was also interesting to read about. As was single, two (90°), and three (120°) phases. -- Grant. . . . unix || die
Re: 3phase power for VAXen [was Re: VAX 780 on eBay]
On 1/4/2022 5:17 PM, Rich Alderson via cctalk wrote: I've been reading this thread for the last few days, without the time to reply. All the statutes of limitations have run out, so I can tell the story; it will be clear shortly why I'm piggybacking on Guy's post. Someday we will all gather around the bonfire, ringed by our black helicopters and will share the tale of Doug's KA10 that ran in his apartment unit. We did not have a 3phase outlet on the second floor of the building where the collection was housed, and there was no room for the first VAX in the small computer room on the third floor, so Ian and Keith came up with an alternative: They tested all the outlets on the second floor and determined that there were three within reach of the room in which Ian was going to work on the 785 which were fed from 3 different phases off the big honking breaker panel (200A service, IIRC). Keith put together a box with the appropriate NEMA socket and three heavy duty cords feeding into it, which in turn were plugged into three outlets on the walls around what eventually became the vintage exhibition hall at Living Computers: Museum + Labs (the eventual name of the place after the modern exhibit space on the first floor was built). It was far worse than that CZ
Re: 3-phase power
On Tue, Jan 4, 2022 at 12:00 PM Adrian Stoness via cctalk < cctalk@classiccmp.org> wrote: > you can use a vfd drives to get 3phase power from single u just gotta size > them bigger then the load u would normally need > > Yes, in principle this is true. In the simplest case, the VFD input is just a 6 diode full wave rectifier into a capacitor. BUT things like power factor correction on modern drives means the input circuit is a lot more complex. Usually the small VFD will be designed for single phase power or 3phase power and the derating is done for you. Using a 3phase drive on single phase typically won't work because the drive will detect a phase loss and shut down. I know for one Rockwell drive there was an internal hack that allowed it to work on single phase so the sales people could plug into a 120vac outlet. Chuck D.
3-phase power; was: cctalk Digest, Vol 88, Issue 2
On 1/4/22 3:14 PM, Jonathan Chapman wrote: >> High-leg delta is independent of open- or closed-delta. > > That's correct. > >> Open delta uses two single-phase transformers primaries connected to >> phases AB and BC. > > A to C is also valid, presumably it's rotated if there's a lot of open delta > in an area (again, why?) to balance phases. In fact, in my neighborhood, each house has a big green disconnect box on the street fed by 3-phase 11KV. Every so often, the utility sends out a notice that they'll be "re-balancing" the distribution. I imagine that that involves nothing more than changing one phase wire in the big green box. I recall a winter after an ice storm that resulted in many power outages (the line workers were complaining that with more than an inch of ice on the HV lines, that the weight would break the pole crossarms. Hope that doesn't happen again. As a consequence, the fuse in our home's transformer blew. The service guy opened the transformer case and then grabbed a 10 foot fiberglass pole; unscrewed the bad fuse and then fitted a new fuse to the pole. He advised that I should put some distance between the transformer and myself, as it wasn't unusual for these things to turn into pyrotechnic displays. > High-leg delta exists so you can have 120/240 lighting and appliance loads in > a building that consumes mostly 3-phase, like a machine shop with an office. > In most areas you aren't allowed to have more than one type of service to a > building (not sure if that's true for double-fed sites, never seen one with > two kinds though). I've heard the Power Company usually doesn't want to > install high-leg delta anymore for a variety of reasons: the load limit, > people not understanding they need to skip a breaker, 120/208Y having become > the usual form of smaller service three phase, etc. When I worked in heavy industry, it was eye-opening to see the range of voltages, phasings and *frequencies* entailed in the operation (we had 25 Hz, 60 Hz and DC). And, of course, the mistakes made by the electricians in installing various equipment. --Chuck
Re: 3phase power for VAXen [was Re: VAX 780 on eBay]
> Date: Tue, 04 Jan 2022 14:44:00 -0800 > From: Van Snyder via cctalk > On Tue, 2022-01-04 at 17:17 -0500, Rich Alderson via cctalk wrote: >> Paul Allen wanted me to acquire a VAX-11/780 for his >> collection > John Zabolitzky has an operating VAX -- I don't know the vintage -- > eleven cabinets, in his collection in Neubiberg, a southeastern suburb > of Munich. > He also has a Cyber 180, Cyber 960, Cray Y-ML EL, Cray T3E, NEC SX-6, > IBM 705, > Photos > at > https://photos.google.com/share/AF1QipPGeVphL95gtsGIO96iU4APdtSRnHhcm1y4-YaPspa6_jDuAZw6cfD3FR3OFr8czw?key=MjJZNUVjMWtLRkVKbmF2TnFDa3ZneDM0WWFqZ0hB Yes, I know about John's collection. Thanks. I suppose I should have pointed out that the story posted took place about 15 years ago, when we were all younger and healthier and living... Rich
Re: 3-phase power
> From: Jon Elson > It should be 208V Oh, right you are. It's been a long time, and I had a distinct memory that it was less than that, but I looked, and I think that's it. The term for my flavour of 3-phase is apparently "open wye/open delta"; each leg is 240V to the others, but only two are 110V to neutral - the "hi leg" (normally colour-coded orange; normal 3-phase uses black/red/blue) is 208V. The page Jonathan Chapman sent had a good diagram of how it is wired: https://www.engineeringradio.us/blog/wp-content/uploads/2012/02/3-phase-open-delta.jpg When they were doing some work on the pole decades back, I asked the foreman how it worked, and he drew a diagram to show me; I had forgotten it, but seeing that, that is it. The A and C are produced off one feed phase, but the B comes from the second feed phase. Noel
DEC HDD heads?
Dunno if this is useful for anyone but the price seems right: https://www.ebay.com/itm/Qty-8-Cdc-Dec-Disk-Head-Heads-75010109-75010101-/255306991030
Re: 3phase power for VAXen [was Re: VAX 780 on eBay]
As the owner of a VAX-11/780 I can confirm what Guy says about the 866 power controller. This is the only component that needs 3-phase power. There is a small 3-phase transformer inside that provides 24V DC to the control circuitry. The power controller not only interfaces to the DEC power control bus to switch on other cabinets (with a delayed output) but also connects to airflow sensors above each blower. If the airflow fails then it cuts power to the system. The blowers themselves are all single phase. I converted my power controller to run on single phase by replacing the transformer (18VAC, 20VA). It's also important to note that the neutral wire from the line filter to the output rail is undersized for running the system on single phase. If the system were running on 3-phase then the neutral current would be minimal but running from single phase means ALL the current is going through neutral wire. I replaced this wire with one of a suitable rating. I am in the UK so the figures I give are for running a system which would normally be on 415V 3-phase from a 240V single phase supply. For 110V you can probably just double the current figures. I have the FP780 option as well as 2x DW780 and RH780 controllers. To power everything in the main cabinet takes about 16.5A. I run this all off a 20A circuit breaker (B-Curve RCBO). I have to turn on the H7100 power supplies one at a time. If I try to turn them all on at once the inrush will trip the breaker. There are two different versions on the H7100 in this system. The older version uses a 3 ohm resistor, which is shorted by a relay after power up, to limit the inrush. These have quite a high inrush current. The later version uses a thermistor in place of the resistor which greatly improves the situation. Once you have the main cabinet powered then to get a usable system you then need about another 4A to run the two BA11K Unibus boxes and whatever power is required for a disk drive. In my case that's usually an RA70 or RA72 so fairly minimal. I don't have any Massbus disks but I do have a TU77 connected to the system. The heating effect is noticeable after the system has been running for a while so you may also have to consider air conditioning power requirements. Matt
Re: cctalk Digest, Vol 88, Issue 2
> High-leg delta is independent of open- or closed-delta. That's correct. > Open delta uses two single-phase transformers primaries connected to > phases AB and BC. A to C is also valid, presumably it's rotated if there's a lot of open delta in an area (again, why?) to balance phases. > On high-leg, one of the secondaries is center-tapped and split > single-phase is fed from the center tap and either end of the secondary. Right, and you get a mostly unusable "high leg" w.r.t. neutral, usually 208V though I don't know what it ends up actually being in open delta with poor/uneven loading. The 120/240 power available is also supposed to be derated, IIRC it's only supposed to be 5-10% of total service load. High-leg delta exists so you can have 120/240 lighting and appliance loads in a building that consumes mostly 3-phase, like a machine shop with an office. In most areas you aren't allowed to have more than one type of service to a building (not sure if that's true for double-fed sites, never seen one with two kinds though). I've heard the Power Company usually doesn't want to install high-leg delta anymore for a variety of reasons: the load limit, people not understanding they need to skip a breaker, 120/208Y having become the usual form of smaller service three phase, etc. > Said configuration can be a 3-winding full delta configuration or the > open-delta as detailed above. Right, there's one or two of those services in town here for a couple of small commercial buildings. Four wire high leg open delta off the pole, two transformers on the pole. Thanks, Jonathan
Re: 3phase power for VAXen [was Re: VAX 780 on eBay]
On Tue, 2022-01-04 at 17:17 -0500, Rich Alderson via cctalk wrote: > Paul Allen wanted me to acquire a VAX-11/780 for his > collection John Zabolitzky has an operating VAX -- I don't know the vintage -- eleven cabinets, in his collection in Neubiberg, a southeastern suburb of Munich. He also has a Cyber 180, Cyber 960, Cray Y-ML EL, Cray T3E, NEC SX-6, IBM 705, Photos at https://photos.google.com/share/AF1QipPGeVphL95gtsGIO96iU4APdtSRnHhcm1y4-YaPspa6_jDuAZw6cfD3FR3OFr8czw?key=MjJZNUVjMWtLRkVKbmF2TnFDa3ZneDM0WWFqZ0hB
3phase power for VAXen [was Re: VAX 780 on eBay]
> Date: Sat, 1 Jan 2022 13:19:51 -0800 > From: Guy Sotomayor via cctalk > On 1/1/22 10:40 AM, Paul Koning via cctalk wrote: >>> On Jan 1, 2022, at 1:12 PM, Noel Chiappa via cctalk >>> wrote: >>> This: >>> https://www.ebay.com/itm/275084268137 >>> The starting price is expensive, but probably not utterly unreasonable, >>> given that: >>> - the 780 was the first VAX, and thus historically important >>> - 780's are incredibly rare; this is the first one I recall seeing for sale >>> in the classic computer era (versus several -11/70's, /40s, etc) >>> - this one appears to be reasonably complete; no idea if all the key CPU >>> boards are included, but it's things like the backplane, etc (all of which >>> seem to be there) which would be completely impossible to find now - if >>> any >>> boards _are_ missing, there's at least the _hope_ that they can be located >>> (780 boards seem to come by every so often on eBait), since people seem to >>> keep boards, not realizing that without the other bits they are useless >> Interesting, but the argument for why it's not tested is implausible which >> makes me very suspicious. I suppose there might be a few American homes >> that have only 110 volt power, but I'm hard pressed to think of any I have >> ever seen, and that includes really old houses. > Without replacing the power controller in the 11/780, you need 208v 3-phase > to run it. It's not impossible...nothing in the CPU actually *needs* 3-phase > as the individual power supplies are 120v but the overall maximum load is > greater than a 30A 120v circuit. > TTFN - Guy I've been reading this thread for the last few days, without the time to reply. All the statutes of limitations have run out, so I can tell the story; it will be clear shortly why I'm piggybacking on Guy's post. Back in the mists of time, Paul Allen wanted me to acquire a VAX-11/780 for his collection. Shortly after that request landed in my inbox, the DECUS DFWLUG announced that they would not be opening their VAX museum due to the untimely passing of the gentleman who was driving the effort, and that they would be disposing of the collection. I contacted the person who was handling the deaccession, but he would not discuss it with me because someone else had already arranged to take the whole collection. That person was Guy Sotomayor. Guy sold Paul two 11/785 systems (one an upgrade, with the 780-5 replacement label!) in chassis, with a third full set of boards as spares. I flew down to the Bay Area and had lunch with Guy, saw his DEC-10 and all that, and arranged for the shipping. Shortly after that, Paul floated the idea of turning the collection into an actual museum. (At the time, the project consisted of me and an electrical engineer named Keith Perez, who devoted his spare time to helping me keep Paul's big iron running. Keith was building the digital control system for Paul's submarine at the time.) The project, an online "museum" called PDPplanet, changed its name to Living Computer Museum; we hired a third engineer to help, Ian King, who was eminently qualified to get the VAXen up and running based on his own private collection of VAXen and -11s in his basement. We did not have a 3phase outlet on the second floor of the building where the collection was housed, and there was no room for the first VAX in the small computer room on the third floor, so Ian and Keith came up with an alternative: They tested all the outlets on the second floor and determined that there were three within reach of the room in which Ian was going to work on the 785 which were fed from 3 different phases off the big honking breaker panel (200A service, IIRC). Keith put together a box with the appropriate NEMA socket and three heavy duty cords feeding into it, which in turn were plugged into three outlets on the walls around what eventually became the vintage exhibition hall at Living Computers: Museum + Labs (the eventual name of the place after the modern exhibit space on the first floor was built). So it's possible to power a 780 or 785 without a power supply rebuild if you simply have the right (industrial) breaker panel in your building... Happy New Year, everybody! Rich
Re: 11/785 on ebay (2018) - was Re: VAX 780 on eBay
> > > Date: Mon, 3 Jan 2022 11:39:01 -0500 > From: Chris Zach > > The thing that always made me wonder is where are all the 8600's. The > 8600 was apparently the best selling large Vax, outselling the 780 and > 750, so what happened to all of them? They weren't any bigger than a 780... > > C > There is an 8650 at the RICM. https://www.ricomputermuseum.org/collections-gallery/equipment/dec-vax-8650 -- Michael Thompson
Re: cctalk Digest, Vol 88, Issue 2
On 1/4/22 12:15 PM, Jonathan Chapman via cctalk wrote: > One of the top Google results: > > https://www.engineeringradio.us/blog/2012/02/the-open-delta-three-phase-service/ > > Really really, there's only two pigs on the pole. And yet, delta power, > though at a lower rating than transformer nameplate (vs. if you had three). As I understand it: High-leg delta is independent of open- or closed-delta. Open delta uses two single-phase transformers primaries connected to phases AB and BC. Secondaries are series-connected and 3-phase output is taken from the high end of either secondary and the common connection. Mostly a cost-savings measure as the efficiency isn't very good. On high-leg, one of the secondaries is center-tapped and split single-phase is fed from the center tap and either end of the secondary. Said configuration can be a 3-winding full delta configuration or the open-delta as detailed above. --Chuck
Re: cctalk Digest, Vol 88, Issue 2
One of the top Google results: https://www.engineeringradio.us/blog/2012/02/the-open-delta-three-phase-service/ Really really, there's only two pigs on the pole. And yet, delta power, though at a lower rating than transformer nameplate (vs. if you had three). Thanks, Jonathan ‐‐‐ Original Message ‐‐‐ On Tuesday, January 4th, 2022 at 14:56, Grant Taylor via cctalk wrote: > On 1/4/22 8:52 AM, Jonathan Chapman via cctalk wrote: > > > Indeed. This is not corner-grounded delta. Once you figure out open > > > > delta, look at dog-leg. > > I did some brief reading on open delta and now think that it requires > > three lines, independent of ground. So I fail to see how open delta > > would be any benefit save for a simpler transformer (fewer coils) or > > fewer transformers. It seems as if you would have the same line and > > insulator cost as more common (closed) delta. > > > > > Grant. . . . > > unix || die
Re: cctalk Digest, Vol 88, Issue 2
On 1/4/22 8:52 AM, Jonathan Chapman via cctalk wrote: Indeed. This is not corner-grounded delta. Once you figure out open delta, look at dog-leg. I did some brief reading on open delta and now think that it requires three lines, independent of ground. So I fail to see how open delta would be any benefit save for a simpler transformer (fewer coils) or fewer transformers. It seems as if you would have the same line and insulator cost as more common (closed) delta. -- Grant. . . . unix || die
Re: 3-phase power
On 1/4/22 10:04 AM, Paul Koning via cctalk wrote: > The other option, typically somewhat more expensive but cheaper than an > 11/780, is a rotary converter. Those are 3 phase motors, sometimes modified > a bit, driven from single phase power that construct the missing phase > somewhat like a dynamotor would. Those things produce proper sine waves so > they are good to use even with things that are picky. Rotary converters can > be found in machine tool supply catalogs. One has to be careful here. The common "idler" type of rotary converter uses a 3-phase motor, with only one set of windings fed from the single phase supply and leading the third phase idle to develop a current that's +/- 90 degrees from the powered phase. So the output looks like 0,90,180, rather than 0 120 240 degrees. Good enough for powering a 3-phase motor with slight derating, but nothing I'd use to power a computer power supply. The second type is similar, but incorporates a dual field arrangement, with a single-phase field coaxial with a 3-phase one comprising a motor. You get much better output phase relationships there and one would probably work fine with a computer. --Chuck
Re: VAX 780 on eBay
On 1/4/22 7:40 AM, Grant Taylor via cctalk wrote: > I guess I thought that since Seymour left CDC to form Cray Research, > that meant that he was more of an employee at CDC and had less influence > on how it operated as a company. I would have assumed that someone that > was a founder would have had more influence and tried to improve things > before splitting off and forming yet another new company. My recollection was over the CDC 8600 project--there is a preliminary document over at bitsavers: http://bitsavers.org/pdf/cdc/8600/Preliminary8600RefMan_Aug72.pdf Sort of a 4-processor 64-bit 7600, but with some important differences, such as discarding the notion of A and B registers and relying on 16 64-bit registers for everything. P-relative branches and calls and out-of-user-space "library" routine use. Apparently, the sharp pencil people were unwilling to fund the thing fully and Seymour left (with the blessings of CDC which owned stock in Cray Research) to do his own thing, along with selection of a few key CDC personnel to help staffing. Afterwards, Cray was forbidden to recruit from CDC ranks for a number of years. At the time, the super-duper-computer funding was being funneled into Jim Thornton's STAR-100 project. You could see a definite difference of philosophy--the STAR was a virtual-memory vector machine (eventually became the ETA-10) with scalar subset facilities, whereas the 8600 was a real-memory fast scalar architecture with no vector facilities. In the end, the Cray-1 wound up with some vector instructions and registers. Funding a system like the Cray I or STAR (or any other supercomputer of the day) required a huge cash commitment and CDC was unwilling to fund *two* such projects. --Chuck
Re: 3-phase power
> On Jan 4, 2022, at 12:00 PM, Adrian Stoness via cctalk > wrote: > > you can use a vfd drives to get 3phase power from single u just gotta size > them bigger then the load u would normally need I've said that too, and I've been told that this is not a good idea for power supplies. Something about the waveforms involved in VFDs. I haven't studied the subject enough to decide whether that's accurate, and the only VFD usage I have is a lathe -- the sort of application VFDs are designed for. The other option, typically somewhat more expensive but cheaper than an 11/780, is a rotary converter. Those are 3 phase motors, sometimes modified a bit, driven from single phase power that construct the missing phase somewhat like a dynamotor would. Those things produce proper sine waves so they are good to use even with things that are picky. Rotary converters can be found in machine tool supply catalogs. paul
Re: VAX 780 on eBay
On Jan 4, 2022, at 4:05 AM, P Gebhardt via cctalk wrote: > > >> There's a photo on twitter: >> >> https://twitter.com/DonaldM38768041/status/1215804561333473280/photo/2 >> >> showing a guy standing before an open one at Fermilab. > > > In of the pictures are shown some very handy tape and disk pack holders on > wheels. I never saw such fancy holders. Would be great to come across one of > those - or better so some myself. > > Cheers, > Pierre The tape cart is just a standard cart for taking tapes between the tape library room and where the tape drives are located. I’ve seen an updated version made for DLT/SDLT/LTO tapes. The disk pack holder on the other hand is something I’ve never seen, I have to wonder if it was custom, and how well it handled an uneven load. Zane
Re: 3-phase power
you can use a vfd drives to get 3phase power from single u just gotta size them bigger then the load u would normally need On Tue, Jan 4, 2022 at 10:52 AM Jon Elson via cctalk wrote: > On 1/4/22 10:03 AM, Noel Chiappa via cctalk wrote: > > > From: Scott Quinn > > > > > I have seen some roads where the utility has 2 of the phases plus > > > neutral going down them, not true 2-phase power, but 2 phases > 120/240 > > > degrees apart with the third phase just not present. > > > > > > > > My house has something like that; the previous owner wanted '3-phase > service' > > for machine tools (I think - could have been a compressor, or something) > in > > his basement workshop, so they sold him a pseudo-3-phase service. I > forget > > the exact details of how it works, but the 3rd phase is at 170V to > neutral, > It should be 208V - see center grounded delta online. 240 * > sin 60 degrees = 207.8 V. > Jon >
Re: 3-phase power
On 1/4/22 10:03 AM, Noel Chiappa via cctalk wrote: > From: Scott Quinn > I have seen some roads where the utility has 2 of the phases plus > neutral going down them, not true 2-phase power, but 2 phases 120/240 > degrees apart with the third phase just not present. My house has something like that; the previous owner wanted '3-phase service' for machine tools (I think - could have been a compressor, or something) in his basement workshop, so they sold him a pseudo-3-phase service. I forget the exact details of how it works, but the 3rd phase is at 170V to neutral, It should be 208V - see center grounded delta online. 240 * sin 60 degrees = 207.8 V. Jon
Re: VAX 780 on eBay
On 1/4/22 9:40 AM, Grant Taylor via cctalk wrote: On 1/4/22 12:14 AM, Chuck Guzis via cctalk wrote: Seymour Cray, along with Bill Norris and Jim Thornton and others left Remington Rand/UNIVAC after Rand bought the near-bankrupt ERA. Apparently, the work environment at Rand was felt to be stifling. Norris had all of the Navy connections and was a great marketer, so bringing some of Rand's engineering talent along was a natural. Interesting. I guess I thought that since Seymour left CDC to form Cray Research, that meant that he was more of an employee at CDC and had less influence on how it operated as a company. I would have assumed that someone that was a founder would have had more influence and tried to improve things before splitting off and forming yet another new company. There are PLENTY of examples of the sole founder being either forced out by the board or shunted aside. See James Ryder or Alan Shugart, who both were forced out, sued to prevent them from using their own names, but then went into competition with their old companies and ran them out of business. Jon
Re: VAX 780 on eBay
> On Jan 4, 2022, at 10:40 AM, Grant Taylor via cctalk > wrote: > > On 1/4/22 12:14 AM, Chuck Guzis via cctalk wrote: >> Seymour Cray, along with Bill Norris and Jim Thornton and others left >> Remington Rand/UNIVAC after Rand bought the near-bankrupt ERA. Apparently, >> the work environment at Rand was felt to be stifling. Norris had all of the >> Navy connections and was a great marketer, so bringing some of Rand's >> engineering talent along was a natural. > > Interesting. > > I guess I thought that since Seymour left CDC to form Cray Research, that > meant that he was more of an employee at CDC and had less influence on how it > operated as a company. I would have assumed that someone that was a founder > would have had more influence and tried to improve things before splitting > off and forming yet another new company. Being a founder doesn't necessarily help much if the company gets big and chairwarmers take control. It's one thing if you're a chairwarmer yourself and rise to CEO, but if you're a top engineer you may be in a non-control position -- especially back then when managers were managers and engineers just did what they were told. For another example, consider Steve Jobs, who didn't even leave Apple voluntarily. paul
StorageTek 9-trk Tape Drive 2925 Restauration
Hello, Has anybody a STC 2925 9-trk Tape Drive. I need a BIN- or HEX-File from an EPROM on the CP--Card. It's the PROM #1 with the number 403936303. Best regards Lothar
Re: 3-phase power
> From: Scott Quinn > I have seen some roads where the utility has 2 of the phases plus > neutral going down them, not true 2-phase power, but 2 phases 120/240 > degrees apart with the third phase just not present. My street has that. The subdivision as a whole has all 3 phases (down the main road through it), but individual streets off of it have only 1 or 2. (The whole subdivision is on poles, so it's easy to see.) On the ones with 2, some houses are connected to one, some to the other. > I guess they figure twice the loads for only one more wire. No, because most homes are only connected to one phase. I think the main reason to do it is that it allows the total load (of the entire subdivision) to be somewhat balanced across all 3 phases. > Can't remember what it was called but I do remember seeing in some book > somewhere about a "phantom 3rd leg" or something My house has something like that; the previous owner wanted '3-phase service' for machine tools (I think - could have been a compressor, or something) in his basement workshop, so they sold him a pseudo-3-phase service. I forget the exact details of how it works, but the 3rd phase is at 170V to neutral, or something like that. (So I can't power any 110V outlets off the third phase.) I think the way it works is that the two 'main' phases are 220V to each other, 110V to neutral (I think from the usual center-tapped transformer off one of the three main feed phases, i.e. 180 degrees to each other). The third 'pase' is generated by a second, smaller transformer connected to the other feed phase in some arcane way I forget the details of. So it's 120 degrees away from the other two. Noel
Re: cctalk Digest, Vol 88, Issue 2
> I apparently need to do more reading. Indeed. This is not corner-grounded delta. Once you figure out open delta, look at dog-leg. Thanks, Jonathan
Re: cctalk Digest, Vol 88, Issue 2
On 1/4/22 8:06 AM, Jonathan Chapman via cctalk wrote: Yes, that's open delta. There are one or two small commercial buildings here in town that still have open high leg delta service -- that's 240V delta, and one of the 240V transformers is center-tapped to give 120/240 split phase for small loads. I'm having trouble reconciling that with my current mental understanding. First I have to bring up line vs phase. My understanding is that the line is the actual wire, and a phase is what runs over the two lines. I can see how you might use two lines combined with a "corner ground" for as the third line for a delta configuration. Thus you have three three distinct line parings ~> phases. L1+G, L1+L2, L2+G. If that is not what's being discussed in this case, then I have no idea what it is. My guess is, aside from saving on wire, insulators, etc. (not significant in town), the real savings is on disconnects and the extra transformer. I apparently need to do more reading. I'm not seeing how corner ground delta will save a transformer. Or I'm completely misunderstanding things. -- Time to research "open delta". -- Grant. . . . unix || die
Re: VAX 780 on eBay
On 1/4/22 12:14 AM, Chuck Guzis via cctalk wrote: Seymour Cray, along with Bill Norris and Jim Thornton and others left Remington Rand/UNIVAC after Rand bought the near-bankrupt ERA. Apparently, the work environment at Rand was felt to be stifling. Norris had all of the Navy connections and was a great marketer, so bringing some of Rand's engineering talent along was a natural. Interesting. I guess I thought that since Seymour left CDC to form Cray Research, that meant that he was more of an employee at CDC and had less influence on how it operated as a company. I would have assumed that someone that was a founder would have had more influence and tried to improve things before splitting off and forming yet another new company. -- Grant. . . . unix || die
Re: cctalk Digest, Vol 88, Issue 2
> I have seen some roads where the utility has 2 of the phases plus > neutral going down them, not true 2-phase power, but 2 phases 120/240 > degrees apart with the third phase just not present. Yes, that's open delta. There are one or two small commercial buildings here in town that still have open high leg delta service -- that's 240V delta, and one of the 240V transformers is center-tapped to give 120/240 split phase for small loads. My guess is, aside from saving on wire, insulators, etc. (not significant in town), the real savings is on disconnects and the extra transformer. Thanks, Jonathan
RSTS V10.1 patch
I just added a patch to https://github.com/pkoning2/decstuff, in patches/shut.cmd, which cures a problem in RSTS V10.1 that seems to come and go with no clear pattern. The failure is a crash, sometimes a halt, during system shutdown. The cause was a write to the wrong location when removing the DCL runtime system, because of a register not being set before that action. The patch can be installed with ONLPAT; it takes effect immediately (because it patches a non-resident overlay). paul
Re: cctalk Digest, Vol 88, Issue 2
On Sun, 2022-01-02 at 12:00 -0600, Grant wrote: > Where are you getting two /different/ phases? -- Remember, the > different legs on residential 120/240 wiring are really the same > single > phase. > > How do you get *two* /different/ phases without access to a *third* > phase? There are only a few places in the U.S.A. (and I'm not aware > of > anywhere else in the world) that actually have 2? power (where the ? > are > 90? out of phase with each other). I have seen some roads where the utility has 2 of the phases plus neutral going down them, not true 2-phase power, but 2 phases 120/240 degrees apart with the third phase just not present. Every time I've seen that it seems like fools economy, but I guess they figure twice the loads for only one more wire. Can't remember what it was called but I do remember seeing in some book somewhere about a "phantom 3rd leg" or something where they used 2 wires with 120/240 degree phase separation into the transformer and then the third phase "corner" was just floating and current would "return" across the other two. As it was brought up in the context of "make sure some yahoo didn't try this on your install and if they did be very careful" and was delta-only I imagine it was not that common.
Re: VAX 780 on eBay
>There's a photo on twitter: > >https://twitter.com/DonaldM38768041/status/1215804561333473280/photo/2 > >showing a guy standing before an open one at Fermilab. In of the pictures are shown some very handy tape and disk pack holders on wheels. I never saw such fancy holders. Would be great to come across one of those - or better so some myself. Cheers, Pierre - http://www.digitalheritage.de
Re: The Prolok Saga (Was: Applesauce FDC
Fred, a completely unrelated piece of information, but interesting nonetheless: Elnec device programmers are very famous for the number of devices it programs and its robustness. Also for their clones. If you open a cloned beeprog you cannot differ it from an original beeprog. I still haven't completely reverse engineered the protection, but it seems to be related to the serial number. If any host software beyond 2.63 detects a "fake programmer" it BRICKS the cloned prigrammer. Yes, rends it useless. You gotta reprogram a pair of eeproms and a pic to make it work back again. You told about the prolok plus erasing hds and I remembered of this atitude from elnec. And no, I know of no one that sued elnec for bricking their clone programmer. So bad. They are great programmers, I have an old beeprog. 73 de pu2sex Alexandre Enviado do meu Tele-Movel Em ter, 2 de nov de 2021 17:35, Fred Cisin via cctalk escreveu: > On Tue, 2 Nov 2021, dwight via cctalk wrote: > > The trickiest protection I've seen is where there is a hole punched > > through the disk on one track. The idea is that the protected program > > writes to that track and expects to see a failure to read that track. > It doesn'tneed to be a hole all the way through, merely any physical > defect that renders that spot unusable. > > The "Physical Defect" protection. > > Copy protected disks had already been made with flawed content to produce > an error on READ, and were easily circumvented by the "duplicate" copy > having flawed content. The next step was to have a physical defect, so > that the protection software would WRITE to the bad track, and confirm > that the track really was damaged. > So, they would scratch the disk. > In the case of Prolok, the check to confirm a physical defect consisted of > writing all zeroes to that area; verifying all zeroes; writing all ones; > and verifying all ones. > > > Vault Corporation produced "Prolok" with a physical defect. To make it > MUCH MORE IMPRESSIVE to investors and clients, instead of a roomful of > people scratching disks with paperclips, they used a "laser fingerprint" > (use a laser, instead of a paperclip). > > Since they gave the same or similar subroutines, that checked for the > defect, to every client, it was cracked with software that would locate > that subroutine, and replace the subroutine call with NOPs or gut the > innards of the subroutine. The cracks were often posted on Compuserve. > (Vault sued Quaid software for "CopyWrite"/"RAMKEY") > https://casetext.com/case/vault-corp-v-quaid-software-ltd ) > > For "cloning" (pirating copies, often with the Central Point Option > board (flux hardware)), software was developed that would > identify the location of the defect, the cloner would then attempt to > scratch the disk at that location, and then the software would locate the > defect and juggle stuff around to put the content in the right place(s) > relative to the defect. > > > But, Vault Corporation wasn't satisfied until they shot themselves in the > foot with very high caliber rounds. > They announced "Prlok PLUS". W. Krag Brotby (chairman of Vault) said that > it would, if it detected a "fake" copy, wipe out the user's hard disk! > Even at the announcement of Prolok PLUS, the computer marketing > community was aghast and enraged. It doesn't take much to realize the PR > nightmare, and the legal liabilities for damaging a customer computer, > even if it was NOT a false positive! > > Ashton-Tate, the largest Prolok client for dBase III, and part > owner of Vault, immediately cancelled their contracts. And announced > that they had done so, that they had never used Prolok Plus, never would, > and no longer used Vault Corporation products. > Almost all of Vault's other clients follwed suit. > > Prolok Plus never made it to market! > 'Course the "word was out". Few people realize that it was NEVER > actually put to use. In fact some of the more idiotic newspaper "solve > your computer problems" columnists, when stumped, would actually speculate > "maybe your computer was attacked by an out of control copy-protection > program." > > > So, we ended up with a mythical monster, and the creator of that mythical > monster was vanquished. > > If anybody can document an actual existence of Prolok Plus, I would like > to hear about it. > > > There is little mention of it on the web, but: > > https://tech.slashdot.org/story/08/06/09/1927205/a-history-of-copy-protection > "Re:Ahhh, holes burned in disks (Score:5, Informative)" > > > https://books.google.com/books?id=9y4EMBAJ&pg=PA19&lpg=PA19&dq=prolok+plus+copy+protection+vault+corporation&source=bl&ots=9Y7SBcnFx9&sig=ACfU3U3JDSEI-QjLjMi1V_gWdPq8gaHrHg&hl=en&sa=X&ved=2ahUKEwjijpjCufrzAhX2TDABHXh2DBgQ6AF6BAgHEAM#v=onepage&q=prolok%20plus%20copy%20protection%20vault%20corporation&f=false > > https://www.pcjs.org/blog/2019/05/05/ > Kryoflux display of Prolok > > -- > Grumpy Ol' Fred >
