At 4:59 PM +0000 9/23/09, Mike Ross wrote: The Computer History Museum's 1401 restoration project has had a great deal of experience with this issue. The first 1401 restored was from Germany - and was configured for 50Hz power. Subsequent to analyzing the issue, it was determined that the best solution was to use a 60Hz -> 50Hz converter. The reason, there were way too many issues of converting the 1401 itself. IIRC, here's the issues to consider: All items containing cores and windings (motors, fans, transformers, etc.) are typically line frequency specific. Some are not - but one has to check them all! Ferroresonant power supplies are almost always "tuned" for a specific line frequency - and will do "bad" things when used at an incorrect frequency. Some switching power supplies support both 50Hz and 60Hz (or even 400Hz) power - but, again, one has to check the specs... Line clocks are tied to the line frequency - and this could affect some software (but this is usually not a huge issue - but it has to be considered). Regards, Lyle -- Lyle Bickley Bickley Consulting West Inc. http://bickleywest.com "Black holes are where God is dividing by zero"

It's best to check the label on the PSU. SMPU's quite often cover the voltage & current ranges with out changing anything. In the case of linear supplies it's usually a strap on the transformer that connects two 110v windings in parallel for 110v and series for 240v. I can't recall any options for frequency changes on a DEC system except for transformers with a cap. across the transformer and line time clock options. Regards Rod Smallwood -----Original Message----- From: cctech-bounces at classiccmp.org [mailto:cctech-bounces at classiccmp.org] On Behalf Of Zane H. Healy Sent: 23 September 2009 21:03 To: General Discussion: On-Topic and Off-Topic Posts; cctech cctech Subject: Re: 50Hz vs. 60Hz At 4:59 PM +0000 9/23/09, Mike Ross wrote: It makes me bit nervous. Does any of it have settings for 50/60Hz? Timing might be an issue. I have one thought, what would it take to get/build a 60Hz to 50Hz power converter that would give you the right frequency and voltages? I used to work on a lot of computer equipment that required 400Hz power, and prior to that I was an electrician and actually maintained the power converters. Zane -- | Zane H. Healy | UNIX Systems Administrator | | healyzh at aracnet.com (primary) | OpenVMS Enthusiast | | MONK::HEALYZH (DECnet) | Classic Computer Collector | +----------------------------------+----------------------------+ | Empire of the Petal Throne and Traveller Role Playing, | | PDP-10 Emulation and Zane's Computer Museum. | | http://www.aracnet.com/~healyzh/ |

At least one type of drive that I've worked on (and I can't remember what it was) had 2 sets (of 4) screw holes for the motor. They were offset by 45 dgrees from each other _and_ one set put the motor further from the spindle pulley than the other set. To do the 50/60Hz conversion you had to change the motor pulley, then unbolt the motor and re-mount it using the other set of holes. The difference in distance between the 2 pulleys meant you used the same drive belt for both frequencies. IIRC most (old) DEC drives used 115V motors, and used the primary of the mains transformer as an autotransformer to run them off 230V mains. The frequency difference wasn't a problem for the motor, it ran fine on either freqeuncy, just at a different speed. Known as 'crowning', at least over here. It's surping the first time you see it, but the pulley is smaller in diameter at the edges than in the mdidle. The belt runs on the largest diameter part -- and mves itself there when the pulleys turn. If you naively make a pulley with a smaller diamter in the middle (with the idea being that he larger diameter edges will keep the belt in place), the belt will fly off. IIRC the OP has at least one 60Hz drive. Which maks life a lot easier. It shouldn't be too hard to turn a replacement pulley. I suspect you can get the profile either by using a form tool, or by swinging the cutting tool as in a sperical turning attachment. The RK05 has a tangential lower fan with a capacitor-run motor. All RK05s have 115V fans [1] and AFAIK there's no change when you change frequency either. [1] Runn of the mains transformer as an autotransformer for 230V mains, of course. The were wired on the 'live' end of the primary winding with the result that the motor insulation has to stand 230V. And some don't. RK05 blowers catching fire is not uncommon over here. -tony

Dave McGuire wrote: FWIW, this shows up with a search for "pulley crowning": http://www.lhup.edu/~dsimanek/scenario/crowning.htm (click thru to the answer page). It looks familiar, I think somebody else pointed to the same page during a previous discussion of this topic on the list.

<4ABC6960.51BB6E at cs.ubc.ca> Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Hi I thought I'd mention that the sight is wrong. There are two different actions. Even a ridgid belt=2C such as a steel belt will walk up the incline=2C as long as it doesn't slip. But the steel belt won't center on the crown unless it is stretched. The steel belt would wobble back and forth. The thinking of this fellow is that the two are the same and they are not. Dwight ---------------------------------------- se e list. =0A= _________________________________________________________________=0A= Insert movie times and more without leaving Hotmail=AE.=0A= http://windowslive.com/Tutorial/Hotmail/QuickAdd?ocid=3DTXT_TAGLM_WL_HM_Tut= orial_QuickAdd_062009=

On Sep 25, 2009, at 6:10 AM, Sridhar Ayengar wrote: Umm. Wow. It never occurred to me to think of the capstan riding in the belt rather than the belt riding on the capstan. -Dave -- Dave McGuire Port Charlotte, FL

Chuck Guzis wrote: It's more than that. If the wheels are profiled to the reverse of the common configuration, the stress on the system is enough to derail the train, even with flanges in place. The flanges do help keep the train on the track on curves (they act sort of like a bump stop at the end of the wheel's "play"), but their primary purpose is to help guide the wheel through the points at switches. The profile of the wheels is one of the main reasons why railroad ties (or sleepers, if you're on the other side of the pond...) are necessary. When a train passes a section of track, it exerts a large amount of force pushing the rails away from each other, because the train is sitting between the rails instead of on them. Next time you're near some worn, straight track, check out the wear pattern. You'll find that the inside of the rails is slightly more worn than the outside. It's very subtle, but you can see it. Peace... Sridhar

The small/cheap UPSes I've had to repair seem to contain one trasnformer which is used as a step-down transformer when the mains input is present (to charge the battery) and as a step-up transformer (driven by the power transitors/mosfets from said battery) when the mains fails. So no way can it change mains of one freqeuncy into another without a second transformer, etc. I wonder if the output waveform of such UPSes (and indeed the inverters you an get to run mains-powered stuff off the car battery) is good enough to run things like RK05 spindle motors. -tony