- How long does it take a microwave oven to warm up? - 14 Updates
- Mesa Boogie Mk4 design shennanigans - 7 Updates
- Composite video from an older laptop? - 3 Updates
- What does decent celestial navigation freeware on Android actually do? - 1 Update
| micky <NONONOmisc07@bigfoot.com>: Nov 30 05:23PM -0500 How long does it take a microwave oven to warm up? I often cook things that take maybe 7 or 8 seconds. Maybe if they're really small they take 5 but it's hard to know in advance and I really dislike most overcooked things. Undercooked, one can just cook it some more but is two 5-second zappings the same as one 10-second zap? Or does it take a second (or 2 or 3 or more) to get the waves churning, so two 5-seconds is more like 9 seconds (or 8 or 6)? I need to know so that eventually I'll know the proper time for a particular food, without stopping and checking**. Has anyone read about this? Or other oscillators? **This actually raises another question. I'm pretty darn good at predicting how much time I need to microwave something, and once in a while I can even remember from experience. (Cocoa from refrigerated milk is 2 minutes. An eggroll of a given size is 2 minutes 40 seconds, even though wrapper says 4 minutes.) But what if part of something much bigger than 10-second food is cooked enough and I take it to the table and start eating and when I get to another part, find that it is not cooked enough. By this time all of it has cooled some. In that case, it's not the microwave warm-up time that would matter, but am I right that there is still food warm-up time? If the food is 70^, it might not even start cooking until the part that cooks reaches, what, let's assume 110. (Or maybe someone has a real number for a given food) So if one is eating for 15 minutes, the 120 degree food will have cooled off to 80 degrees, and if I put it back in, it still has to get back up to 110 again, before it even starts cooking again, is that right? That could take 20 or 30 seconds or more, depending on how much food there is and other details. I dont' mind the extra time, but I would like it if someone could provide real-life numbers so I could better estimate how long the 2nd part of the cooking will take. |
| FromTheRafters <erratic@nomail.afraid.org>: Nov 30 05:45PM -0500 micky explained on 11/30/2016 : > How long does it take a microwave oven to warm up? The energy transfer is nearly immediate. The oven only warms up because of the food warming up. Some items which I microwave would end up having cold or cool spots, so I used to cook say a three minute item by cooking for two minutes and then allowing the heat to spread for a couple of minutes, and then zap for another minute or so. I now have a new microwave oven with a turntable (the other had a reflector) to help avoid the spottiness. The ovens power output is also an important factor to consider. |
| jurb6006@gmail.com: Nov 30 03:09PM -0800 When you get down to thing that only take a few seconds, the fact that it takes about two seconds for the magnetron filament to warm comes into play. Usually you can hear the fan slow down once the microwaves are really being produced. |
| Jon Elson <jmelson@wustl.edu>: Nov 30 05:16PM -0600 micky wrote: > How long does it take a microwave oven to warm up? The heater in the magnetron tube takes a couple seconds to warm to the point where it will emit electrons. You can hear it easily on the old transformer microwaves, the fan starts and it begins to hum, then a couple seconds later the hum gets much louder. That louder hum is when the magnetron tube starts conducting. Newer microwaves with switching power supplies may delay turning on the HV until the heater has warmed up, and they may not have that transformer hum, so it may be harder to tell when the RF comes on. Jon |
| Frank <"frank "@frank.net>: Nov 30 06:41PM -0500 On 11/30/2016 5:45 PM, FromTheRafters wrote: > I now have a new microwave oven with a turntable (the other had a > reflector) to help avoid the spottiness. The ovens power output is also > an important factor to consider. I find it easier to microwave for longer periods of time at a lower setting to get even heat. |
| whit3rd <whit3rd@gmail.com>: Nov 30 03:51PM -0800 On Wednesday, November 30, 2016 at 3:41:20 PM UTC-8, Frank wrote: > > an important factor to consider. > I find it easier to microwave for longer periods of time at a lower > setting to get even heat. It takes a few seconds to heat the filament of the vacuum tube. So, it's advisable to use longer times, but NOT lower setting (which just adds multiple ON/OFF switching to the problem). To get something a 5 second zap, you might be well advised to put a cup of water in next to your nibble, and give the pair ten seconds. The water load will slow the nibble heating, and the longer time means the turnon variability is less important. It also gives your turntable a chance to do a full revolution under full magntron power (better hotspot control) |
| "tom" <tmiller11147@verizon.net>: Nov 30 06:57PM -0500 "Jon Elson" <jmelson@wustl.edu> wrote in message news:0sidnaf7d81CwaLFnZ2dnUU7-UednZ2d@giganews.com... > hum, > so it may be harder to tell when the RF comes on. > Jon Stick an old CD in the MW and you can see exactly when the RF power starts. |
| FromTheRafters <erratic@nomail.afraid.org>: Nov 30 07:33PM -0500 Frank formulated the question : >> an important factor to consider. > I find it easier to microwave for longer periods of time at a lower setting > to get even heat. Yes, the new MW oven has programmable settings for power level and rest periods and such for better results. The old one only had a single knob with minute marks on it and a bell that softly, almost inaudibly, went 'click' when the time expired. The old one is 26 years old, but it still works. |
| jurb6006@gmail.com: Nov 30 06:17PM -0800 >"I find it easier to microwave for longer periods of time at a lower setting to get even heat. " Yeah but they generally only turn it on and off. The duty cycle controls the power level. I have only see one microwave in my life that actually had separate taps on the transformer for lower power. |
| jurb6006@gmail.com: Nov 30 06:19PM -0800 >"Stick an old CD in the MW and you can see exactly when the RF power starts. " Really. Never thought of that. |
| Mike Duffy <mqduffy001@bell.net>: Nov 30 11:20PM -0500 On Wed, 30 Nov 2016 17:16:05 -0600, Jon Elson wrote: > Newer microwaves with switching power supplies may delay turning on the HV > until the heater has warmed up, and they may not have that transformer hum, > so it may be harder to tell when the RF comes on. +1, You are the only one who did not lambast the OP for using the term 'warm up' to mean 'cause the ambient MW intensity to reach its operational range'. When I am judging time for extremely small loads (like softening butter without liquifying it), I allow 4 seconds for my oven. I find that the hum does not get louder though. Instead, I notice that the fan speed lowers a bit, presumably because the supply voltage for the fan is then being loaded down by the power consumption by the magnetron. |
| micky <NONONOmisc07@bigfoot.com>: Nov 30 11:26PM -0500 In sci.electronics.repair, on Wed, 30 Nov 2016 19:33:00 -0500, >with minute marks on it and a bell that softly, almost inaudibly, went >'click' when the time expired. >The old one is 26 years old, but it still works. I had an Amana Model 2, that looked just like the drawings of microwaves that were used for decades. It lasted many years. I got it used around 1975 and met its earthly demise around 2000. . Although the insulation on the diodes had failed** and it sparked, so I covered the open parts with GE silicon sealant, and something else I fixed, and eventually the power transformer broke, I think it was. They wanted 300 dollars for it and my pointing out that they should take 80 since I coudl buy a new one for 80 didn't help. They lowered the price to the repairmans price of 200 roughly. **Amanda didn't want to send me a schematic. I had to beg, and promise I knew what I was doing and wouldn't kill myself. She relented. |
| micky <NONONOmisc07@bigfoot.com>: Nov 30 11:30PM -0500 In sci.electronics.repair, on Wed, 30 Nov 2016 18:57:51 -0500, "tom" >> until the heater has warmed up, and they may not have that transformer >> hum, >> so it may be harder to tell when the RF comes on. I'll go with "a couple". Thanks. >> Jon >Stick an old CD in the MW and you can see exactly when the RF power starts. That sounds like it might work |
| micky <NONONOmisc07@bigfoot.com>: Nov 30 11:30PM -0500 In sci.electronics.repair, on Wed, 30 Nov 2016 15:09:58 -0800 (PST), >When you get down to thing that only take a few seconds, the fact that it takes about two seconds for the magnetron filament to warm comes into play. Sure. That's what I had in mind. >Usually you can hear the fan slow down once the microwaves are really being produced. I'll pay more attention. Thanks and thanks all. |
| "Gareth Magennis" <soundserviceleeds@outlook.com>: Nov 30 09:05PM "Phil Allison" wrote in message news:efdd5f94-6779-43ba-aa28-0a9fb53520a1@googlegroups.com... Gareth Magennis wrote: > didn't > bug out at the reduced voltage, so perhaps this was a dodgy quad of ECC83, > of perhaps something to do with the Cryogenic process? ** I doubt they put the valves directly in liquid N2 - as it would destroy them instantly by cracking the glass. Even if done some other and safer way, the whole idea is completely nuts. One of the design issues with valves is the vacuum tight seal between the pins and the glass base - cos steel and glass do not have the same tempco of expansion. Typically, steel has a higher tempco so the fit get tighter as the glass envelope heats - conversely it gets looser at very low temps. Prolonged exposure at very low temps could let air ( or N2) into the vacuum and spoil the operation. .... Phil My bad, their website makes no mention of N2. Maybe they just stick them in the freezer and call it Cryo. Interesting info though. Anyway, any thoughts on 5.1v heater voltage as a viable propostion? Cheers, Gareth. |
| "Gareth Magennis" <soundserviceleeds@outlook.com>: Nov 30 09:29PM "Phil Allison" wrote in message news:efdd5f94-6779-43ba-aa28-0a9fb53520a1@googlegroups.com... Gareth Magennis wrote: > didn't > bug out at the reduced voltage, so perhaps this was a dodgy quad of ECC83, > of perhaps something to do with the Cryogenic process? ** I doubt they put the valves directly in liquid N2 - as it would destroy them instantly by cracking the glass. Even if done some other and safer way, the whole idea is completely nuts. One of the design issues with valves is the vacuum tight seal between the pins and the glass base - cos steel and glass do not have the same tempco of expansion. Typically, steel has a higher tempco so the fit get tighter as the glass envelope heats - conversely it gets looser at very low temps. Prolonged exposure at very low temps could let air ( or N2) into the vacuum and spoil the operation. .... Phil Oh, OK, rather late to the party on this one - so there is no bonding at all between the pin and the glass, just an interference fit? Gareth. |
| "pfjw@aol.com" <pfjw@aol.com>: Nov 30 01:44PM -0800 On Tuesday, November 29, 2016 at 9:37:28 PM UTC-5, Phil Allison wrote: > ** I doubt they put the valves directly in liquid N2 - as it would destroy them instantly by cracking the glass. Even if done some other and safer way, the whole idea is completely nuts. > One of the design issues with valves is the vacuum tight seal between the pins and the glass base - cos steel and glass do not have the same tempco of expansion. Typically, steel has a higher tempco so the fit get tighter as the glass envelope heats - conversely it gets looser at very low temps. > Prolonged exposure at very low temps could let air ( or N2) into the vacuum and spoil the operation. I do not believe they do, either. Here is one "Cryo" vendor describing their process: _______________________________________________________________ The BLACK SABLE process is far more than putting tubes in a chamber and lowering the temperature. The BLACK SABLE process starts with tube selection. Only the best preamp, power and rectifier tubes are chosen to undergo this arduous process. All tubes undergo a 24 hour burn-in under load. The tubes are then placed in the Cryo-Processor where a computer-controlled proprietary system lowers the temperature to -300 Fahrenheit / -184 Celsius for 24 hours and then slowly ascends back to room temperature. Preamp tubes are tested and rated for Gain, Microphonics and Noise. Next, all 7/9 pin tubes have their pins cleaned for a better electrical connection. Power tubes are matched to within 3% for both Ip (Plate Current) and Gm (Transconductance). No other cryogenic process comes close. When only the best will do, choose BLACK SABLE. __________________________________________________________________________ Which is 21F above the boiling point of liquid nitrogen, a cheap and readily obtainable material in liquid form. That being written, most metals, including coated steel, copper, cupro-nickel and other solderable materials have a vastly greater coefficient of expansion/contraction than even the softest glass (Pyrex). So either the pins are going to shrink out of their surroundings, or all this is done in a *hard* vacuum. There is no real danger of shattering the glass if done slowly, but as the pins will be *smaller* than the opening during the process - that is where all the 'magic' must take place. Color me dubious. Peter Wieck Melrose Park, PA |
| etpm@whidbey.com: Nov 30 04:34PM -0800 On Wed, 30 Nov 2016 13:44:18 -0800 (PST), "pfjw@aol.com" >Color me dubious. >Peter Wieck >Melrose Park, PA Especially dubious because if the pins really did shrink away from the glass the glass/metal seal would be broken and the tube would leak air in once exposed to the atmosphere again. When tubes are made the glass really does seal to the pins, just like glue. But glass is elastic (more elastic than the metal pins) and the movement would be small so maybe the glass does move with the pins. Steel pins on a tube would shrink about .0001" going from room temp to 300 below. Glass would move about .000067" so about 33 millionths of an inch difference. So the glass/steel seal would probably hold. Eric |
| Phil Allison <pallison49@gmail.com>: Nov 30 05:11PM -0800 > glass the glass/metal seal would be broken and the tube would leak air > in once exposed to the atmosphere again. When tubes are made the glass > really does seal to the pins, just like glue. ** True when the steel pins are as hot as the molten glass that is formed around them. But this happens at a very high temp ( about 1500C ) so during cooling thermal contraction will put considerable stress on this seal even at room temp. .... Phil |
| Phil Allison <pallison49@gmail.com>: Nov 30 07:13PM -0800 Gareth Magennis wrote: > In this case dropping from 6.1v to 5.1v. > I'm no expert in valve amp design, but this seems to be rather a strange > design choice. ** The same idea was used by MusicMan in several models to create a half power switch. I did a quick test on a few 'X7 and 'U7 types and found good operation was maintained to under half voltage on the heaters. At about 2 volts instead of 6.3V, voltage gain is low or sub unity. .... Phil |
| jurb6006@gmail.com: Nov 30 08:27PM -0800 Low filament voltage was used to do a "life test", at least on CRTs. If the emission dropped like a rock it was deemed that the tube was close to failure. I do not really know how accurate the test was, no way to get the data really. But it did not drop it to half, something like maybe 70 % or so. This liquid nitrogen bullshit really sounds like audiophoolery. First of all how would it work ? What would be the theory behind it. Just because it got cold it somehow changed the characteristics of the cathode coating ? Because it can't do much else. The grids are just wires and the plate is just a piece of metal. I think if they wanted to make a better tube they would bombard it more with heat, like they do CRTS, which were put into a very demanding application and required special treatment. Don't depend on the getter. That would evaporate more gases out of the elements before the getter is even involved, and I would guess this was done before the glass envelope was on it. That would seem logical. However it still doesn't make sense. The solubility of a gas into a solid goes down with higher temperature and of course the reverse is true. What does that mean in this case ? I am not sure. Maybe they want some nitrogen in the tube, but only a small amount. This would of course increase leakage and slow the electron flow, but some might find the sound more pleasing. Seems to me it would add distortion but if you are talking a guitar amp that distortion is like gold to some artists. However, the leakage and probably lower gain would probably make it more likely that reduced heater voltage would take it out of the operating range where it was intended in the amp. Then of course it does not work. And then we got the thermal coefficient of the resistance of the heater itself which would inherently pull more current at a lower voltage. The tube book is kinda like the transistor book, when it says so many mA at a certain voltage it means it, but not so much at lower voltages. How that curve would be affected by dunking it in liquid nitrogen is beyond me, it could but it would take a metallurgist to figure it out. Like heat treating, now they got cold treating. OK. It still sounds like a bunch of audiophoolery to me. What's more the customer should have noticed that the low power ode quit working when the tubes were changed and simply changed them back, but he took it to a shop. No accounting for brains with some people. Like where I used to work at the music store. These fuckers don't know the difference between line level and mic level. They have an effects box and the complaint is that it pops when switching modes. Well they got it plugged in between the guitar and amp when it is supposed to be in an effects loop on a mixing board. And they are selling this shit not even knowing how it is supposed to work ? And how many times I had a problem with hum come back to them using a speaker cable for low level input. And then blowing the low level cables using them for multi-hundred watt amps. So now I am working where they sell karaoke machines. ALL of one model seems to have low mic gain. They gave me a 400 ohm mic for the bench, it is simple that ALL of this model has low mic gain, it needs a high impedance mic. One comes in with that complaint and the customer says "I use good mics, Shure SM-58 (I think)". So I look it up and the thing is even lower impedance than what I have. That is like trying to use a moving coil cartridge on a stereo that does not have the proper input for it. (preamp that is) Some mics have a built in transformer for that, but not the SM-58 as far as we could tell if I got the model number correct. I am almost thinking that this problem is due to the characteristics of the heaters of these tubes, not any cryogenic process. Unless it literally is nitrogen in the tubes. What does nitrogen do to the getters ? Anyone know ? Air turns them all white and flaky, whatever boils out of the elements in the tube makes them brown, the atmosphere makes them white and it is mostly nitrogen. But nitrogen is generally non-reactive except when you burn it so hot it oxidises like in a car combustion chamber, thus the need for an EGR valve. Other than that, while not a noble gas, it is pretty close. And tubes do not reach those temperatures encountered in a combustion chamber. Another interesting but useless subject, but then what are we here for anyway ? Maybe we gain knowledge and take advantage of some of the audiophoolery. I got kicked off one forum and the one I am on now is even more nuts. A twenty grand preamp, and get your own phono stage and DAC while you're at it. Five subwoofers but never turn the bass up. Move the furniture to where the Wife is pissed off to get the best sound. Like people used to do home theater, they do home sound rooms. I am talking additions to the house just for the stereo. Of course you can stick a big TV in there, but those listening sweet spots are not all over the place. And the more shit you got the worse it gets. And now we got guitar amps that automatically bias the tubes no matter what you put in there, and sockets that will accept a 6BQ5 as well as a 6550. (KT88//6L6 or whatever) I think this is getting a bit out of hand myself, but if it is a way to make money fine. Just charge enough. |
| Ralph Mowery <rmowery28146@earthlink.net>: Nov 30 12:07PM -0500 In article <f0b17cf2-8f09-4589-8cc1-9cc16f0350fc@googlegroups.com>, captainvideo462009@gmail.com says... > I have an old Dell Lattitude D630 laptop. Is there a way to come out of the VGA jack on the back of my laptop and somehow end up with composite or S video out? I tried an adapter that my son said he had used to do this in the past. It plugs into the RGB jack in the back and it has two short cables out of it. One has an RCA female jack on the end of it and the other has an S video female. I didn't try S but although I can get an image on my composite monitor you can see that there is more than one image and it's out of sync. I tried adjusting the display settings and that seems to put the frequency way off. I used to have a video board on an old DOS computer that had an RCA jack on it and it was very handy. Is this still possible to do? I think that I read somewhere that anything ten ears older or less should be able to support this. I don't know how old my laptop is but i don't think that it's over ten years. Thanks, Lenny Ebay has lots of converters like that. I have not tried them,but they don't cost much to try. Here is one for $ 10. http://www.ebay.com/itm/VGA-to-TV-RCA-Composite-Converter-Adapter-S- video-Box-for-PC-Laptop-Windows-Mac-/111867988250? hash=item1a0bda091a:g:YLkAAOSwSHZWgz4n They are usually from $ 10 to $ 30. |
| whit3rd <whit3rd@gmail.com>: Nov 30 03:56PM -0800 > I have an old Dell Lattitude D630 laptop. Is there a way to come out of the VGA jack on the back of my laptop and somehow end up with composite or S video out? I tried an adapter... The laptop has to supply sync-on-green for a simple adapter to work. Can you interrogate the video output mode, or change it, to make interlaced 60 Hz video with sync-on-green? More flexible (expensive) adapters actually include frame buffers, and require a power supply. |
| "Michael A. Terrell" <mike.terrell@earthlink.net>: Nov 30 09:22PM -0500 whit3rd wrote: > The laptop has to supply sync-on-green for a simple adapter to work. Can you interrogate > the video output mode, or change it, to make interlaced 60 Hz video with sync-on-green? > More flexible (expensive) adapters actually include frame buffers, and require a power supply. Used Extron scan converters show up on Ebay for reasonable prices. VGA to S-Video or composite are common models. There is a steady stream of older hardware being pulled out during upgrades to digital and mixed video systems. -- Never piss off an Engineer! They don't get mad. They don't get even. They go for over unity! ;-) |
| The Real Bev <bashley101@gmail.com>: Nov 30 09:10AM -0800 On 11/30/2016 07:45 AM, Jeff Liebermann wrote: >>eye as the old eye was so bad. > Thanks. I'm 68 solar revolutions old, so that's a real possibility. > No sign of cataracts, but I'm borderline with glaucoma. High pressure, drops, no damage yet? Likewise. The main reason I had my cataracts done was to get rid of the astigmatism (which glasses were never able to fully correct and which made contacts very nearly useless), and it worked really well! > friends have had cataract surgery and opted for strange combinations, > such as one eye optimized for close work, and the other for distant > and driving. They all say that it can be quite functional. I wouldn't dream of having permanent monovision (one eye for distance, one for near), but I have contacts like that. The brain deals with it -- mostly -- but there's a certain amount of ghosting unless the light is really bright. My daughter doesn't even notice that with hers. > Nobody > mentioned color, but I'll ask. Cataracts turn the lens yellow. I was really surprised to see the difference in color between the two eyes. (I waited months to have the second eye done -- I wanted to be SURE!) The brain makes everything work together (my ski goggles are yellow, but within a minute or so the snow is all white again; when I take the goggles off the snow is slightly blue for a while), so it's not a real problem -- just interesting. -- Cheers, Bev "The object in life is not to be on the side of the majority, but to be insane in such a useful way that they can't commit you." -- Mark Edwards |
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