dleigh@hplabsz.HPL.HP.COM (Darren Leigh) (05/12/89)
Well, "board-swapped" would be a better term. Does this make me an offical customer engineer? :-) I didn't really want to try to fix the amiga power supply itself without schematics so I bought a 200W AT clone power supply for $60 and used that. Since the power supply cases weren't the same form factor, I couldn't just slide the new one in. Thanks to defacto manufacturing standards that the PC industry has (thanks to evil IBM), the boards inside the two power supplies were practically identical and I just put the new board inside the old case. Some connectors and wire later, I had a power supply that worked nicely, minus the TICK line which was the one subtlety. I take it that this has some sort of 60 Hz clock on it? My 2000 didn't work until I changed jumper J300 from "normal" to "A500". What do I gain/lose by not having a power supply TICK? Will it matter at all? Are the schematics for this jumper wrong? For "normal" operation, the schematics say that J300 should be jumpered between pins 2 and 3. I found it jumpered between 1 and 2 and had to change it the other way to get it to work without the TICK line. What's going on? P.S. Mucho thanks to C-A for putting the 2000 schematics right in the back of the intro. manual which is included with every machine. Also kudos for making the TICK line jumperable. I hate having to cut and solder. ======== Darren Leigh (415) 857-6713 (w), (415) 967-8102 (h) Internet: dleigh@hplabs.hp.com UUCP: hplabs!dleigh
andy@cbmvax.UUCP (Andy Finkel) (05/12/89)
In article <3319@hplabsz.HPL.HP.COM> dleigh@hplabs.UUCP (Darren Leigh) writes: >60 Hz clock on it? My 2000 didn't work until I changed jumper J300 >from "normal" to "A500". What do I gain/lose by not having a power >supply TICK? Will it matter at all? Normally, the A2000 takes its 1/60sec (or 1/50) ticks from the power lines, which should be fairly accurate. When you switch the jumper to the "A500" position your A2000 then takes its ticks from the video. Which is not quite as accurate. -- andy finkel {uunet|rutgers|amiga}!cbmvax!andy Commodore-Amiga, Inc. "Do or Do Not. There is no Try." - Yoda, explaining the loop constructs in JCL (Jedi Control Language). Any expressed opinions are mine; but feel free to share. I disclaim all responsibilities, all shapes, all sizes, all colors.
doug@xdos.UUCP (Doug Merritt) (05/13/89)
In article <6854@cbmvax.UUCP> andy@cbmvax.UUCP (Andy Finkel) writes: >Normally, the A2000 takes its 1/60sec (or 1/50) ticks from the power >lines, which should be fairly accurate. When you switch the jumper >to the "A500" position your A2000 then takes its ticks from the >video. Which is not quite as accurate. Unless there is something more going on than what you stated, this is inaccurate. Power line frequencies drift quite a bit, although the utilities usually take some care to make the drift average out to approximately zero over a period of time. Whereas crystal-derived video timing is as accurate as the crystal, a difference of several orders of magnitude. The intuitive way to see the difference is to look at the accuracy of an old fashioned analog electric wall clock driven purely by power line frequency, versus newer crystal driven digital watches or wall clocks. I've never heard of the former being accurate to within a few seconds per year, but the latter are. Doug -- Doug Merritt {pyramid,apple}!xdos!doug doug@xdos.com Member, Crusaders for a Better Tomorrow Professional Wildeyed Visionary "Of course, I'm no rocket scientist" -- Randell Jesup, Capt. Boinger Corps
daveh@cbmvax.UUCP (Dave Haynie) (05/15/89)
in article <3319@hplabsz.HPL.HP.COM>, dleigh@hplabsz.HPL.HP.COM (Darren Leigh) says: > Summary: B2000 power supply fixed! > I take it that this [TICK] has some sort of > 60 Hz clock on it? My 2000 didn't work until I changed jumper J300 > from "normal" to "A500". What do I gain/lose by not having a power > supply TICK? Will it matter at all? The TICK from the power supply gives you a 60Hz signal derived from the AS line frequency, which is regulated by most power companies so that digital clocks can be real accurate. The CIA chip that drives the software clock is based on this. If you use the "A500" position, the timebase will instead be based on the vertical sync frequency. This is slightly off from 60Hz, I don't recall exactly how far, though the end result is that you're clock won't be quite as accurate. Genlocks will often cut the vertical sync pulse every other frame, so unless you're using a genlock or you're in need of a real accurate TOD clock, you probably won't notice the change of the jumper. > Are the schematics for this jumper wrong? For "normal" operation, the > schematics say that J300 should be jumpered between pins 2 and 3. I > found it jumpered between 1 and 2 and had to change it the other way > to get it to work without the TICK line. What's going on? Far as I know, the jumper's in right, though occasionally things do get swapped between schematic and actual layout. From what you've said, the jumper was in the right place as shipped, and you now have it in the A500 position. > P.S. Mucho thanks to C-A for putting the 2000 schematics right in the > back of the intro. manual which is included with every machine. Also > kudos for making the TICK line jumperable. I hate having to cut and > solder. I figured that allowing the 2000 to use the A500 method of clocking would help out if anyone ever wanted to power the 2000 from a DC supply, or if someone ever found a legidimate use for having the TICK line synced to the frame sync. I guess you found another use... > Darren Leigh (415) 857-6713 (w), (415) 967-8102 (h) > Internet: dleigh@hplabs.hp.com > UUCP: hplabs!dleigh -- Dave Haynie "The 32 Bit Guy" Commodore-Amiga "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: D-DAVE H BIX: hazy Amiga -- It's not just a job, it's an obsession
dleigh@hplabsz.HPL.HP.COM (Darren Leigh) (05/16/89)
In article <286@xdos.UUCP> doug@xdos.UUCP (Doug Merritt) writes: >In article <6854@cbmvax.UUCP> andy@cbmvax.UUCP (Andy Finkel) responds to my question about the TICK signal and J300. >>Normally, the A2000 takes its 1/60sec (or 1/50) ticks from the power >>lines, which should be fairly accurate. When you switch the jumper >>to the "A500" position your A2000 then takes its ticks from the >>video. Which is not quite as accurate. > >Unless there is something more going on than what you stated, this >is inaccurate. Power line frequencies drift quite a bit, although >the utilities usually take some care to make the drift average out to >approximately zero over a period of time. I guess Andy means that the TICK signal taken from the video is clocked at 59.94 Hz (the NTSC vertical rate) instead of 60 Hz (the power-line rate). If this is true, then the real-time clock will lose about 86 seconds a day. Ouch! I suppose this is not much of a problem if the user reboots at least once a day, but would be intolerable if the machine is left on continuously. What else is controlled by the TICK signal? The context switch interrupt? The real-time clock problem alone is enough to make me want to build a precision 60 Hz clock signal for the TICK line. What should the signal look like? A TTL level square wave at 60 Hz, duty cycle unimportant? ======== Darren Leigh Internet: dleigh@hplabs.hp.com UUCP: hplabs!dleigh
andy@cbmvax.UUCP (Andy Finkel) (05/16/89)
In article <286@xdos.UUCP> doug@xdos.UUCP (Doug Merritt) writes: >In article <6854@cbmvax.UUCP> andy@cbmvax.UUCP (Andy Finkel) writes: >>Normally, the A2000 takes its 1/60sec (or 1/50) ticks from the power >>lines, which should be fairly accurate. When you switch the jumper >>to the "A500" position your A2000 then takes its ticks from the >>video. Which is not quite as accurate. > >Unless there is something more going on than what you stated, this >is inaccurate. Power line frequencies drift quite a bit, although >the utilities usually take some care to make the drift average out to >approximately zero over a period of time. Exactly. The power companies (at least the ones around here) swear up and down that they average the power line frequency so your clocks don't get wildly inaccurate. When we derive the tick from the video, we are treating an almost 1/60 sec signal as a 1/60 sec signal...which produces a minor inaccuracy. -- andy finkel {uunet|rutgers|amiga}!cbmvax!andy Commodore-Amiga, Inc. "Do or Do Not. There is no Try." - Yoda, explaining the loop constructs in JCL (Jedi Control Language). Any expressed opinions are mine; but feel free to share. I disclaim all responsibilities, all shapes, all sizes, all colors.
charles@hpcvca.CV.HP.COM (Charles Brown) (05/16/89)
>> Normally, the A2000 takes its 1/60sec (or 1/50) ticks from the power >> lines, which should be fairly accurate. When you switch the jumper >> to the "A500" position your A2000 then takes its ticks from the >> video. Which is not quite as accurate. > Unless there is something more going on than what you stated, this > is inaccurate. Power line frequencies drift quite a bit, although > the utilities usually take some care to make the drift average out to > approximately zero over a period of time. > Doug Not correct. The power companies are already quite good during the day. Then near midnight they adjust their frequency so that the total number of cycles in the day is right on. You should see no drift unless you are experiencing power outages. Naturally the power company cannot adjust the main station to compensate for an outage in just one neighborhood. Considering that most outages (in my experience) last less than 2 seconds, with a mechanical clock you would only notice that your clock drifted over a matter of months. -- Charles Brown charles@cv.hp.com or charles%hpcvca@hplabs.hp.com or hplabs!hpcvca!charles or "Hey you!" Not representing my employer. This article is based exclusively upon and generated by transmission line noise.
randy@jato.Jpl.Nasa.Gov (Randy Hammock) (05/17/89)
In article <1410017@hpcvca.CV.HP.COM> charles@hpcvca.CV.HP.COM (Charles Brown) writes: > The power companies are already quite good during the >day. Then near midnight they adjust their frequency so that the total >number of cycles in the day is right on. You should see no drift >unless you are experiencing power outages. ... I seem to recall reading a few years ago that the power companies regulate the line frequency such that a clock that derives its timing from the power line will be accurate within +/-3 sec/yr. Unless you are looking for instantaneous stability, the power line is one of the best sources to drive a TOD clock. If you want anything better, you could get the HeathKit clock that has the WWV receiver built-in such that it decodes the NBS WWV time codes.
jms@doctor.Tymnet.COM (Joe Smith) (05/18/89)
>The intuitive way to see the difference is to look at the accuracy of >an old fashioned analog electric wall clock driven purely by power line >frequency, versus newer crystal driven digital watches or wall clocks. >I've never heard of the former being accurate to within a few seconds >per year, but the latter are. But just because a quartz clock is capable of being accurate to a few seconds per {month,year}, it doesn't mean that your particular crystal has been adjusted to be that accurate. A much better example is to consider a simple digital clock that is driven purely by power line frequency (one without battery backup). Once set, the time displayed will be accurate within plus or minus 2 seconds after one day, after one week, after one month, after one year. That's right, the error is non-cumulative. The power companies guarantee that the long term average is exactly 60 cycles per second, for this very reason. I set my clocks using WWV as a reference (303)499-7111. The battery backed clock on my VCR gains 10 seconds a week. It is very consistant; after 6 weeks it is a minute fast. But the other VCR which counts 60Hz pulses shows no detectable drift after 6 months of uninterrupted operation. The clock on my Amiga 2000 is also fast. What I don't like is that it requires manual intervention to adjust it. It's a hassle, removing the top and adjusting the cap by trial and error. I'd love to see a self-adjusting battery-backed clock circuit. One that has a line frequency input and compares the time of day from the 60 Hz clock with the time of day from the quartz crystal and adjusts itself if there is a difference. -- Joe Smith (408)922-6220 | SMTP: JMS@F74.TYMNET.COM or jms@tymix.tymnet.com McDonnell Douglas FSCO | UUCP: ...!{ames,pyramid}!oliveb!tymix!tardis!jms PO Box 49019, MS-D21 | PDP-10 support: My car's license plate is "POPJ P," San Jose, CA 95161-9019 | narrator.device: "I didn't say that, my Amiga did!"
FelineGrace@cup.portal.com (Dana B Bourgeois) (05/31/89)
Joe Smith would like a crystal clock that adjusts itself long-term from the power line which makes a good long-term time standard but relatively poor short-term one. I like the idea but I'm not sure conceptually how you would design this. At any instant the power line time interval will be long or short. When do you decide to 'sync' up to it? Or maybe you sample the intervals over a week, take the average and set your crystal frequency to that? Or sample over a 30 hour period since the power companies supposedly average over a day? How many samples? Anybody have an idea of how to design this? Dana
eachus@mbunix.mitre.org (Robert Eachus) (06/01/89)
In article <18978@cup.portal.com> FelineGrace@cup.portal.com (Dana B Bourgeois) writes: >Joe Smith would like a crystal clock that adjusts itself long-term from >the power line which makes a good long-term time standard but relatively >poor short-term one. I like the idea but I'm not sure conceptually how >you would design this. At any instant the power line time interval will >be long or short. When do you decide to 'sync' up to it? Or maybe you >sample the intervals over a week, take the average and set your crystal >frequency to that? Or sample over a 30 hour period since the power >companies supposedly average over a day? How many samples? Anybody >have an idea of how to design this? This is a thoroughly studied problem, but from the opposite direction. If you are runninng a production line and are concerned with say the final product weight, you measure the weight of units as they come off the end of the line. But how do you know when to make adjustments? If you adjust for each unit produced, the variance increases, so statisticians have done a lot of work on rule for making adjustments which minimize both the bias and variance. I think the original work was done by Dennison in the thirties, but check any good library under the heading of statistical quality control. This problem is slightly different in that you are changing the yardstick, not the thing being sampled, so I imagine that to use some of the techniques correctly you will have to correct the remembered samples to reflect the new clock rate. Robert I. Eachus with STANDARD_DISCLAIMER; use STANDARD_DISCLAIMER; function MESSAGE (TEXT: in CLEVER_IDEAS) return BETTER_IDEAS is...