On 5/15/2006 at 8:32 PM Evan Koblentz wrote: Some folks run 3 phase machine tools from single-phase lines using a phase converter--basically a big 3 phase motor and a large capacitor. I don't know how well that would work with power supplies, but it's a thought. -Chuck

On 5/15/2006 at 10:13 PM Sridhar Ayengar wrote: You've got a nice one. :) Most phase converters tend to look like this: http://www.metalwebnews.com/howto/ph-conv/ph-conv.html The interesting property of this kind is that as the load increases, the more balanced the phases become. Some old mainframes used 3-phase 400 Hz power. Cheers, Chuck

On 5/16/2006 at 1:07 PM Sridhar Ayengar wrote: I've heard that utility companies really hate the idler-motor kind of phase converter. Apparently the PF of these things is nothing short of goshawful. On the other hand, the home windpower hobbyists(?) will sometimes take large three-phase induction motors and rework the rotor to use neodynium permanent magnets. Apparently, the result is an alternator that puts out a fair amount of power at low RPMs. So maybe there's some grist for someone's "do-it-yourself" rotary MG converter setup--though I'd hate to think about how squirrely the output frequency would get. Cheers, Chuck

On 5/16/2006 at 1:32 PM Sridhar Ayengar wrote: It's both the phase converter itself and the driven load. Here's an interesting explanation: http://www.phaseconverterinfo.com/phaseconverter_voltagebalance.htm What with IGBTs now being in the "affordable" range, maybe the best idea is a solid-state unit. Cheers, Chuck

Kevin Handy wrote: How do they work? One of the ones I was trying out used a full-time capacitor network, but it cost waay too much and didn't have the kind of load capacity I was looking for. The PF was pretty good, though. Peace... Sridhar

Considering this started out from the IBMCollectables point of view, and has drifted a bit off topic :) Having been involved with trade shows in the past, I can assure you the best solution for a one/two day event is to rent or buy a generator. I am aware of a number of high horsepower industrial applications that run on chopped DC that is produced by separate multi fuel generators. While Evan is confident of more show space next year, I do not think a running System/3 would be the best use of that space. Where the S/32-S/36 were built for small business and small office electrical requirements. The System 3 has a M/G, and power is not negotiable with that beast. The most basic configuration, CPU, front Desk console, and card punch and reader takes up a big footprint. Not to mention the choice of printer and disk drive power needs.. Off the top of my head, my wish list would be for a clean quiet generator. Then for a custom trailer where people can walk through much like the NASA display trucks. Well hell, anyone at NASA ready to scrap a display truck that is not total trash ? Lets Dream Big ..... The other Bob :)

Paul Anderson wrote: Is it a permanent-rectifier model? If so, and if it has a high enough power rating, I would be interested. Peace... Sridhar

On Tuesday 16 May 2006 01:42 pm, Kevin Handy wrote: I read about these things from time to time in some of the machining and CNC groups I follow (there are a LOT of them I'm subscribed to). The devices is most often referred to as a "VFD", for variable-frequency drive, often used to drive the spindle of a mill or similar, and give you variable speed with a 3-phase motor. -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, a critter that can be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin

Which picture? Point me to the link. -----Original Message----- From: dwight elvey [mailto:dkelvey at hotmail.com] Sent: Tuesday, May 16, 2006 10:48 PM To: cctalk at classiccmp.org Subject: RE: VCF East 3 -- pictures here Hi There is an interesting machine with what looks like a drum. It looks like some kind of home built. Is there a description of it? Dwight

That was based on a project in a book, its current owner located it in canada and was very interisting to talk with. It was my moms favorite at the show :) The other Bob On Wed, 17 May 2006 07:22:23 -0400 (EDT), Mike Loewen wrote:

Hi I finally have some success in getting a hard drive working on my M20 ( this is the machine with a Z8001 ). I wish to thank Tony, Berry and Fred for there input that helped along the way. I still have some issues but all have work arounds. 1. The BIOS sets the step rate too fast for the ST251. It seems to be around 2.5ms. I found the ST251 doesn't like more than 3ms. I wrote a program that I put on my boot floppy that sets it to 4.0ms. Does anyone know the correct step rate for the st251? I'll have to hack the BIOS some day to fix this. 2. The BIOS sets the precomp somewhere near cylinder 120. The st251 has no precomp and uses the pins as part of the head select. I've made a cut and jumper on my controller card to stop the RWC signal from going to the drive and the MFM generator chip. Again, this needs a BIOS hack. 3. I still don't know exactly where or the format of the bad sector map. I do know it is on one of the first 32 sectors and all 0's seems to indicate that there are no bad sectors. My drive has no bad sectors listed on the lable but if some else wants to use a st251 on the M20, they might need to know how to set this up. I had to do a couple of other hacks to the controller board I'm using but they are related to the boards original use ( a Tandy 5 Meg disk drive and controller ). I've not looked at the 5 Meg disk that came with it. It might have something interesting on it for the TRS80 folks but they most likely have everything someplace on the web already. We are still finding bits and pieces of code and documents for the M20's , even though there were many sold in Europe. M20's are just a little rare now. Most were sold to businesses and they tend to throw things out when they get obsolete. I'm always looking for more M20 owners that might have some software or manuals that can be added to the collection of items we are trying to save. I wonder if there are any more on this list? Dwight

Hi Chuck It definitely doesn't like stepping at around 2 to 2.5 ms someplace. I send the value 8 to the controller that is suppose to be 4.0 ms and that works fine. I don't know how a buffered seek would work on a MFM drive? Are you saying that it should take in what ever step pulses I send it and step at 8ms, regardless of what I send. That doesn't seem to be the case with my drive. I is definitely stepping at the rate I give it with a seek or restore command. I hope I'm not overdoing it too much with the 4.0ms. The stepper is right on the edge of quieting down at that rate. Similar to the optimizer programs that set the step rate for the floppies. It is right below the resonent speed. At 8.0ms it is really harsh sounding. Dwight

Hi Chuck I gave it a try and yes, it works great. The WD1000 spec says that a value of 0 whritten to the step value would do 10 uS steps. This did just as you decribed. Thanks. Dwight ---snip----