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micky <NONONOmisc07@bigfoot.com>: Feb 26 03:39AM -0500 Thanks for the reply pf, but I'm still interested in the questions.     Years ago, I was told not to play my stereo with no speakers, for fear of somethun' or other. Of course that was 1968, a good year for audio.   Is this still an issue with current electronics, like audio amplifiers and burglar alarm amplifiers?     So if I take the fuse out of the circuit to the sirens, but the siren driver is still functioning, do I risk burning it out? Even if it's like this for say, 20 hours? Or can it go like this with no harm to itself?   (These 3 questions are still important regardless of whether I disconnect the siren driver from the control board.)   But.. what if I disconnect the siren driver from the control panel (which I did)? They're separate boards. Do I risk burning out the output of the alarm control panel, if say it is run. again, 20 hours? Or can it go like this with no harm to itself?

Pat <pat@nospam.us>: Feb 26 06:27AM -0500 On Sun, 26 Feb 2017 03:39:55 -0500, micky <NONONOmisc07@bigfoot.com> wrote:   >(which I did)? They're separate boards. Do I risk burning out the >output of the alarm control panel, if say it is run. again, 20 hours? >Or can it go like this with no harm to itself?   That was only ever a problem with tube (valve) designs. No load could cause the output voltage to rise enough to damage some components. I am not aware of any modern equipment with similar restrictions. When transistor outputs arrives to replace tubes, that was one of the big advantages. You didn't want to short the outputs, but having them open was no problem at all.

jurb6006@gmail.com: Feb 26 08:44AM -0800 >"That was only ever a problem with tube (valve) designs. "   That is only partly true. Solid state amps that have output transformers or chokes are also vulnerable. In fact Delco car radios had a warning sticker on them that read "DO NOT OPERATE WITHOUT LOAD". Those were a class A open ended stage simply running into an inductor, but it did produce more power than the SESAPP at a given voltage. It was actually capable of almost nine wattts nto eight ohms but they didn''t bias them hard enough to hit that level without distortion.   Any amp that uses an outpur transformer or choke can be damaged if operated without a load. The old tube stuff, what was actually the problem there was the tube sockets themselves because of the unbridled inductive kick when they got clipped with no load.   I've been in the argument about tubes and don't want to dwell on it, but one thing to remember is that a triode is still a diod, a tetrode is still a diode. When you get to a pentode maybe not so much because of the suppressor grid, but most of the other ones simply do not conduct in reverse. Generally the output devices and transformers could handle the voltage, what happened alot was that the tube sockets arced over.   The failure mode is different in a solid state unit. The inductive kick causes forward current to flow in the collector to base junction and the transistor really does not like that.   From what I've read a bit more recently, because there are still tube amps around, especially for guitars and these high MFs might forget to plug in the speaker, (oh, I got tons of stories about musicians, I mean, nice guys usually but electroncs is like speaking Martian to some of them) now some designs include a diode to ground from the plates of the output tubes. This limits, actually damps, the inductive kick in case a speaker is not connected. However one tech around here reported that he had some problems adding such diodes to an existing design, and I never got the full details on that. It's just not something I have explored and queried about.   Anyway, getting to the OP here, the main thing is simply to look at the unit and see if it uses an output transformer or choke. If not, most solid state equipment can run full blast for decades into no load. However, not knowing the impedance of the guy's siren or whatever, there might be a step up transformer to drive it. Actually that would tend to be less susceptable to such damage than an output circuit that steps down.   When they got to OTL (output transformerless) SESAPP (series arranged, single ended push pull) circuitry the danger was pretty much gone unless the design itself was defective. Or people. I remember working on a Harmon Kardon Citation 12 and people said you could use 2N3055 for outputs. NOPE. The voltage Vcb is not high enough. Now in THAT case because the load is not pulling down the power supploy rails there might be a prblem, especially iif you have transistors that are margnal. Those ratings on the spec sheets are MINIMUM, or WORST CASE. Personally I just use 2N3773s in something like that, which have a nice smooth gain curve as well.   Bottom line, most stuff doesn't care if there is a load. Exceptions are far and few between unless you deal with old stuff or tube stuff. This is supposedly an alarm system, and those barely existed in 1963 when this could be an issue.

mike <ham789@netzero.net>: Feb 26 03:26AM -0800 On 2/26/2017 12:12 AM, Andy Burns wrote:   > [*] not sure about 10Gbe and faster, I've only used it over fibre, and > with a switch between devices, but I would expect it to be auto over > copper too.   You're never gonna need one...until about a week after you dispose of it. Better to have and not need than to need and not have.

Ralph Mowery <rmowery28146@earthlink.net>: Feb 26 10:21AM -0500 In article <o8uduv$qa3$3@dont-email.me>, ham789@netzero.net says...   > You're never gonna need one...until about a week after you > dispose of it. > Better to have and not need than to need and not have.     That is the way it is for everything. I worked at a plant that was built about 1965. At that time there was a spare part that looked like a big auger. It was about 10 feet long and a foot in diameter. It laid around in the way up to about 2005. We got a new plant manager that had us get rid of all things we had not had to replace in the last 5 years. Out went the auger. Wouldn't you know it , a month later it was needed to replace a bad one. Same as with another piece of equipment . I forgot what it was, something like a 20 HP motor and gear box. It was sold as scrap. Before it left the plant site it was needed and we had to buy it back for a lot more than it was sold for.   I have not seen it, but heard that some new cars do not even have a spare tire now,but come with a can of Fix a Flat. Might be fine for a nail hole, but if there is a large cut in the tire,itwill be useless.

frank <frank@invalid.net>: Feb 26 12:38PM > had one left and this one had the G2 wire.   > According to Diemen, the 6098 does have an active pin 1:   > http://www.hrdiemen.com/reparation/flyback/scheme/6098   That's where I checked too. The schematic of the TV clearly shows some connections from the pin 1 to the rest of the circuit and the actual PCB matches too.   > no?). Here's a pic of the actual transformer. Does yours look like this > print and all?   > http://www.electronic-spare-parts.com/descript/h/hr_6098.htm   it looks very similar. The print is on another place, but it says HR 6098.     > H.V. transformers are not difficult to make but H.R. transformers are > premium, so it wouldn't surprise me if someone didn't try to stuff a cheap > Asti Magnetics transformer into an H.R. box.   Whatever... I'll try to ask for a replacement or money back. It isn't clearly what it is supposed to be. Best regards   Frank

frank <frank@invalid.net>: Feb 26 12:40PM > On Sat, 25 Feb 2017 18:29:37 -0000 (UTC), frank <frank@invalid.net> > wrote:   > What is a LOPT? I'm guessing it's a Picture Tube (CRT), but after   Line OutPut Transformer. I should have called it flyback maybe

Sjouke Burry <burrynulnulfour@ppllaanneett.nnll>: Feb 26 11:51AM +0100 > schematic or a photo showing what is what.....   > This is the first time I have ever run across a PCB labeled in > chinese...   Get the ground connection with your ohm meter on each block. Attach a small speaker to each terminal block, if your print is mono. If stereo, use two 20 ohm resistors to connect the other side of the speaker to the l/r in/out points.   Connect power.   Then tap on the speakers, and the outgoing one will echo that, with the one on the input acting as microphone.   Keep the speakers away from each other, or you will have a siren.

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