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spamtrap1888@gmail.com: Feb 06 08:45AM -0800 On Monday, February 2, 2015 at 3:17:21 PM UTC-8, Scotophor wrote: > I'm seeking some out-of-production discrete through-hole component LED light bars for a project. There are two different styles that I want and can not substitute. According to a couple of archived internet postings, they were reportedly manufacturer-discontinued in either the late 1970s or early 1990s, but remained somewhat available until around 2000 because at least two distributors had bought the manufacturers' remaining stocks as surplus and sold them in retail packaging.   Consider the possibility that they were discontinued because they were not very satisfactory. That is a LOT of epoxy in there. Stress from the encapsulant on the die, exacerbated by the heating of the die from the power dissipation, will promote the growth of defects, which raises the dark current, which accelerates the wearout of the die.   More concisely, you wouldn't want to locate a cache of these ancient parts, only to have to go through them like Kleenex.   The discussion on the other forum, where the fellow will overmold conventionally encapsulated LEDs in the desired form factor for you, sounds far more promising.

spamtrap1888@gmail.com: Feb 06 01:37AM -0800 This Zenith DVD2381 has worked for years, except for a spell a few years ago when the tray would shudder but not quite open and close. I managed to free it up.   So tonight, when there was nothing on TV, my wife told me that when she had tried to play a DVD on Tuesday, it didn't work. She tried to turn it off, but the light in the power button stayed on. Nothing appears on the display: no "Hello," no "No disc," no nothing.   We tried unplugging it and plugging it in again, but that did not help.   The thing still looks pristine inside, so I hate to junk it without giving repair a shot.   Does this sound like a simple problem to fix?   How do laser safety interlocks work on those old DVD players? If the lid were off, would that stop all functionality? My SWAG is that this is not working.   Many thanks in advance for any suggestions.   Mike

N_Cook <diverse@tcp.co.uk>: Feb 06 11:59AM > that this is not working.   > Many thanks in advance for any suggestions.   > Mike   try googling model number and "badcaps"

jurb6006@gmail.com: Feb 05 05:23PM -0800 Guy wants to use a powered speaker, I tbink a "Technical Pro" brand with a microphone. I couldn't get a print on it but I see there is nothing wrong with it. The boss thinks you should be able to do that but the fact is it SAYS LINE on it. Tht means it is meant to be fed by a mixer or something, right ? Not a microphone or guitar pickup.   There is no distortion and in the relatively simple circuitry there is almost no way you would lose gain without some distortion. Does anyone really think the AC bypass cap for the feedback is bad ? I don't. Not when every other cap in the thing doesn't seem to be causing a problem. It has clean output and nothing drastic in the frequency response.   Anyway, the ¼" jack is what they seem to want to use. From the line input there it goes through a 33K resistor to the inverting input of an OP AMP (one side of a 4558). I paralleled a 10K with that resistor, making it what, about 8K ? Arond in there. Technically this should just about triple the gain or so but bring down the input impedance. Should be OK for a mic or even a guitar pickup.   I can't reverse engineer this whole damn thing, but have a question.   In case that the customer already has a low impedance mic and wants to use it, really I should be able to decrease the value of that restitor to like 200 ohms. I should get the required voltage gain but it will load the input a hell of alot more, probably to the point of having a problem with other sources. Not just the impedance but the gain, if someone was to plug a mixing board into it, it probably would not work correctly. (maybe to say the least)   However they would still have the line level XLR jack for that. If they had a mixer with only ¼" output, that should be adaptable to that input right ? Because it will have stock gain, I am not modifying that one. That is a little too much reverse engineering to do something wrong. Just use the damn ¼".   Anyway, I am just wondering if there are any unforseen ramifications to cranking that value down to like 200 ohms. Another thing is protecting the OP AMP. If somneone plugs a powered mixer in there is it possible to blow that OP AMP ? Figure a 200 ohm. Can that damage a standard 4558 such as used in these things ? Should I look for a special 1/100th of a watt resistor for this ?   I am sure it can blow it if some goob connects a speaker output to it. But will a well buffed line level possibly kill it ? I don't care that much about the OP AMP, I care more about the thing being walked back into the shop. think, the person using it might not be aware of all the intense gain... I don't care about waking up the neighbors I care about shit coming back for stupid reasons.   I already told the PTB that the unit is working right, and does not have low level imputs. They don't seem to care and want to make it usable this way. Really, I should stick a sticker on it that it is modified, but if I go that far I could really just drill a hole and put a switch on it.     Penny for your thoughts.

Phil Allison <pallison49@gmail.com>: Feb 05 10:26PM -0800 jurb....     > In case that the customer already has a low impedance mic and wants to use it, really I should be able to decrease the value of that restitor to like 200 ohms.   ** Try a resistor of 680 kohms first.   That gives you a gain of 48 times, which should be OK with most dynamic mics, and does not load the mic too much even if it' a 600ohm model.   Any more gain and you will lose high frequencies and have a lot of noise.     .... Phil

jurb6006@gmail.com: Feb 06 02:18AM -0800 >"** Try a resistor of 680 kohms first. "   Not gonna work. I did't really splain it right I guess. This was a 33K running from the ¼" jack to the - imput of an OP AMP. The gain control is connected from the output to the input, which makes it control the gain. It is pribably a friggin 100K at least so even changing it to a one meg is not likely to get what he wants. And I do not feel like looking for the right pot to modify it.   The + is grounded, it is in inverting mode. It is a 4558.   I could cut the fucking foil to the +, put the input to that and then set the gain alot higher I am sure. But that is not easy. I would have to cut all the way around the pin and shit.   But then I do have a board with a bunch of 4558s IN SOCKETS so aybe I can do something with that.   Hell maybe just build a fucking preamp and be done with it. Put the thing back stock. How long will a 4558 run off a 9 volt battery lol ?   No, I would put it inside the in it and just run off its supply. I am in no mood to fuck around. Actually I will but I don't want them bitching about tinme on job because that is when the big test comes. I am making shit money, my idea is to do it the right way, to deliver the customer the fixed product in a reasonable time. I knowe alomost nothing of the rsates but they are low, rtoo low. The company might wat to give those rates as a "courtesy" to their customers, but they are not going to do it at my expense.   But anyway, that is all about what is worth it and what is not, and actually that the owner of the business does not understand about a line input. you cannot just plug a mic in there.   And if this is store stock I will have to snack him upside the head. just tell the guy it needs a preamp, like a mixer, to get enough gain. then you sell TWO units instead of one.   I ant ot say - "Why am I surrounded by such ignorance/" but reallly you gotaa give peole a chance. How would they know what I know. I been selling knowledge for good money for forty years. How WOULD they know.   I have learned a bit of tolerance actually. It pays. Just pay me for now. Lett me become a significant part of your business.   Then you are mine motherfucker. And there ain't mo "lol" on that. done it before and I'll do it again. Fucking assholes deserve to have theire popckets clipped by the likes of me because I make them that money.   I have already had that call. "Get in here as soon as possible". Case closed. I am working this one to fruition if possible.

Tim R <timothy42b@aol.com>: Feb 05 09:08AM -0800 On Thursday, February 5, 2015 at 11:35:42 AM UTC-5, Jeff Liebermann wrote: > repeatedly. This is a safety feature as having the trip value > increase would eventually make the circuit breaker not trip at all. > Magnetic circuit breakers don't have this problem/feature.   I looked this up some time ago for the larger circuit breakers such as those in a main panel.   The manufacturers give specs for the number of cycles.   That number is very large for a circuit breaker being used as a switch to turn a circuit on and off. Many times lighting circuits, e.g., are operated with a breaker and don't have a switch. I don't remember offhand but I'm thinking in the range of 50,000 cycles.   Then you have the next case where the breaker "trips" on overcurrent. You have the toaster on when the refrigerator cycles, etc. You've exceed the 15 amp by enough to trip the breaker but it's not a dead short. The number of rated cycles goes down by a couple orders of magnitude but it's still high.   But now you have the dead short case, where you draw maximum fault current until the breaker trips. Breakers are only rated for 1 to 2 cycles of this kind of duty.

Jeff Liebermann <jeffl@cruzio.com>: Feb 05 09:49AM -0800 On Thu, 5 Feb 2015 09:08:16 -0800 (PST), Tim R <timothy42b@aol.com> wrote:     >That number is very large for a circuit breaker being used as a switch to turn a circuit on and off. Many times lighting circuits, e.g., are operated with a breaker and don't have a switch. I don't remember offhand but I'm thinking in the range of 50,000 cycles.   >Then you have the next case where the breaker "trips" on overcurrent. You have the toaster on when the refrigerator cycles, etc. You've exceed the 15 amp by enough to trip the breaker but it's not a dead short. The number of rated cycles goes down by a couple orders of magnitude but it's still high.   >But now you have the dead short case, where you draw maximum fault current until the breaker trips. Breakers are only rated for 1 to 2 cycles of this kind of duty.   Sorta. There are many ways to use a circuit breaker, each with their own unique way of causing problems. In my case, my collection of assorted breakers came from a power supply that I designed, where I made a big mistake. I used an AC rated breaker for the DC output. Bad idea.   The contact material for AC and DC breakers are quite different. DC breakers have a much larger spring to deal with the tendency for arcing and welding the contacts when opening a high current DC circuit under load. I did some crude testing and found that after tripping about 10 times under 3x rated load, the contacts would weld. The same breaker, with a 3x AC load seemed to work just fine. Moral: Don't use AC only rated breakers with DC.   I didn't have much trouble using such a breaker as an on/off switch on the AC side of the power supply. By much, I had to install a PTC thermistor inrush current limiter on the AC line because the rather large inrush current was sometimes tripping the breaker immediately after it was turned on.   The breakers in my pile are the "push to reset" flavor and are not used as an on/off switch.   A 5 amp breaker will conduct 5 amps forever and not trip. The time-current curves are far from linear or simple: <https://www.google.com/search?q=circuit+breaker+trip+curves&tbm=isch> For example, a "typical" breaker will require about 3 minutes to open at 2x the rated current, and about 0.1 sec at 10x the rated current.   After my initial screwup, I spent some time looking at such time-current curves trying to select a proper circuit breaker. It would have been much easier if I were allowed to use a combination thermal-magnetic breaker, but those were far too expensive.   One could also use a PTC inrush current limiter as a temporary fuse. Too much current and it gets hot and goes "open". The problem is selecting the right combination of on-resistance and trip current. <http://en.wikipedia.org/wiki/Resettable_fuse> I've had to go through the design process a few times trying to find a suitable replacement for such a device, that had burned itself to a cinder and no parts list was available. There's no problem at either extreme of low current and over-current. However, the dissipation reached a peak in between these two extremes. At some current, usually just below the trip point, it gets VERY hot but does not open. Be careful with these.     -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann <jeffl@cruzio.com>: Feb 05 09:11PM -0800 On Thu, 05 Feb 2015 09:49:52 -0800, Jeff Liebermann <jeffl@cruzio.com> wrote:   >Too much current and it gets hot and goes "open". The problem is >selecting the right combination of on-resistance and trip current. ><http://en.wikipedia.org/wiki/Resettable_fuse>   Argh, that's wrong. Clarifying my muddle:   An inrush current limiter is an NTC (negative temperature coefficient) device. When cold, it has a high resistance. As current heats up the device, the resistance goes down. <http://en.wikipedia.org/wiki/Inrush_current_limiter>   An electronic fuse is a PTC (positive temperature coefficient) device. When cold, the resistance is low. When too much current goes through the device and it becomes hot, the resistance goes up. <http://en.wikipedia.org/wiki/Resettable_fuse>   -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558

Leif Neland <leif@neland.dk>: Feb 05 08:16PM +0100 > Where are you, UK maybe ? I can tell you that is not how it is in the US. > There is always alot of L-R material. I can't stand it really. I just don't > watch it anymore   L-R = out of phase. I think there are still monaural (1-channel) tv-sets, which would loose sound if the entire signal was L-R   Leif   -- Je suis Charlie

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