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etpm@whidbey.com: Feb 07 09:12AM -0800 >(I still think the best Thermostats made were those old round Honeywell >ones with the mercury switch. They lasted decades and never needed any >repairs. So much for so called "improved technology"). The thermostat on my wall, a moden programmable type, also has batteries and will not work without them. I don't understand why it was not made to be powered by the furnace. It has a mechanical relay inside, a reed relay I think. I can hear it when it switches on and off. The 3 AAA batteries will power it for about 3 years. Eric

"pfjw@aol.com" <pfjw@aol.com>: Feb 07 09:40AM -0800 > inside, a reed relay I think. I can hear it when it switches on and > off. The 3 AAA batteries will power it for about 3 years. > Eric   As it applies to two-wire heat-only stats:   a) Imagine a programmable thermostat that wiped-and-reset at each power failure. b) Furnace/boiler power can vary from micropile DC up to 24V AC. c) Imagine an expensive device that could be spiked very easily from many sorts of causes.   Hence the need for batteries. All the on-board relay does is switch the AC to the unit. Furnace/Boiler power is entirely isolated from the thermostat power.   Not to mention the additional complications with 5 and 7 - wire heat-pump systems.   Peter Wieck Melrose Park, PA

"pfjw@aol.com" <pfjw@aol.com>: Feb 07 09:44AM -0800 > Not to mention the additional complications with 5 and 7 - wire heat-pump systems.   > Peter Wieck > Melrose Park, PA   Small correction/clarification: The *micropile* (thermocouple driven by the pilot light) fires a *millivolt* gas valve. Usually, such devices operate at/around about 0.700 VDC or so. And the typical thermocouple puts out about 0.750 DC - or *just enough*.

Ralph Mowery <rmowery28146@earthlink.net>: Feb 07 01:10PM -0500 In article <386dbce2-9c67-45a1-8c4c-d385ea1a2f8c@googlegroups.com>, pfjw@aol.com says...   > Not to mention the additional complications with 5 and 7 - wire heat-pump systems.   > Peter Wieck > Melrose Park, PA   If designed correctly the thermostat should hold all its memories during a power giich or fail without depending on the batteries. It should have some short back up battery or 'super capacitor' to keep the time for a few hours or more.   I would want it powered by the furanace for the problems stated above. Dead batteries and none in the house late at night or snowed in.

Jeff Liebermann <jeffl@cruzio.com>: Feb 07 11:00AM -0800 On Tue, 7 Feb 2017 09:40:24 -0800 (PST), "pfjw@aol.com" <pfjw@aol.com> wrote:   >As it applies to two-wire heat-only stats:   If a digital thermostat only had to run a furnace, life would be easy. However, it's also used for heat pumps, staged HVAC, solar, radiant (pump with pipes in the floors and walls), exhaust fans, etc. Note the maze of wires and functions. <https://xtronics.com/wiki/Thermostat_signals_and_wiring.html> However, I think the real reason they run on battery is that batteries are cheaper and smaller than a regulated, protected, and approved power supply.   -- 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

ggherold@gmail.com: Feb 07 11:04AM -0800 > ever change the temperture anyhow.   > My question is how does this sort of thermostat switch the furnace on > and off? Is it a semiconductor type of switch or what? I'm guessing it could be any of those. mechanical relay or SS relay.   > (I still think the best Thermostats made were those old round Honeywell > ones with the mercury switch. They lasted decades and never needed any > repairs. So much for so called "improved technology"). When my battery wore out years ago I wired in the Mercury relay that was right next to the new electronic one. (previous home owner had not removed it.) Like you it was at night and I just wanted heat. I've never un-wired the Mercury switch. To me it seems like the perfect technology for controlling a furnace.   George H.

etpm@whidbey.com: Feb 07 11:11AM -0800 On Tue, 7 Feb 2017 09:40:24 -0800 (PST), "pfjw@aol.com" <pfjw@aol.com> wrote:     >Not to mention the additional complications with 5 and 7 - wire heat-pump systems.   >Peter Wieck >Melrose Park, PA If the thermostat only turned the furnace on and off I could see battery power because there would be only two wires. But my thermostst will and does control much more and there are several wires connected to it. Not only that, my house is only 8 years old so the furnace is a modern one. A memory backup battery I can understand but my thermostat uses the barreries to power the complete thermostat, even powering the mechanical relay. And anyway, either the memory is non-volatile or there is a super capacitor on board because the memory is not lost when the batteries are replaced. Eric

oldschool@tubes.com: Feb 07 02:45PM -0600 >there is a super capacitor on board because the memory is not lost >when the batteries are replaced. >Eric   When I changed the batteries for a second time yesterday, the digital numbers were still there after I removed the batteries, but by the time I opened the batt package they faded away.   I just have 2 wires. I had a new furnace installed this last Novemnber. It still only has 2 wires. The guy never even touched the thermostat.

oldschool@tubes.com: Feb 07 02:48PM -0600 >inside, a reed relay I think. I can hear it when it switches on and >off. The 3 AAA batteries will power it for about 3 years. >Eric   My two AAA batteries lasted 4 years and 3 months. I checked my paperwork for when that 'stat was installed. Like I said, I never knew it even had batteries or I would have changed them long ago.

oldschool@tubes.com: Feb 07 02:51PM -0600 On Tue, 7 Feb 2017 09:44:28 -0800 (PST), "pfjw@aol.com" <pfjw@aol.com> wrote:   >And the typical thermocouple puts out about 0.750 DC - or *just enough*.   Since tou mentioned thermocouples, I always wondered how they produce a voltage. I've probably installed/replaced at least 10 of them, but never understood how they work to create a voltage.....

Michael Black <et472@ncf.ca>: Feb 07 04:08PM -0500

"pfjw@aol.com" <pfjw@aol.com>: Feb 07 01:08PM -0800 On Tuesday, February 7, 2017 at 1:10:53 PM UTC-5, Ralph Mowery wrote:   > for a few hours or more.   > I would want it powered by the furanace for the problems stated above. > Dead batteries and none in the house late at night or snowed in.   OK, I'll bite.   a) A micropile/millevolt system will not make enough power to operate an electronic programmable thermostat. Here in this region of very much older houses, many of which had central heat first installed in the 1930s, many of which are gravity-types (both air and radiators), such furnaces are probably 10% of the operating base. There are several on my block alone. b) So, let's exclude that base and go with standard systems (2 - wire for now). Voltage can be anywhere from 12VAC to 24VAC. Ours is a 24V system (WM Ultra). Our neighbor is at 12V. So, at the very least the stat would have to convert from AC to DC, be smart enough to understand both 12 & 24V, keep a super-cap or rechargeable battery charged and so forth. Adding to the cost. d) And, of course, we are still left with potential spiking issues - and it is not exactly as if one might unplug a thermostat in the case of nasty weather, storms, or potential power-outages.   These are $40 items unless one wishes to get a "Nest" or some similar device. With all these refinements, probably the cost would double.   As it happens, all this applies even more-so to heat-pump stats as large motors (and associated spiking) are involved, as well as many more variations in voltage and functionality assigned to those 5-7 wire stats - some of which are even proprietary by brand. Those, as it happens, are often mains-powered via the system, due to that complexity.   Writing for myself, our 'annualized battery program' includes smoke/heat/gas detectors, the thermostat, the flashlights (car and house) wireless mice and similar devices. Removed-still-good batteries go into things like my radios that take D or C batteries, remote-controls and other non-critical items until death. As we use only name-brand batteries with good warranties, and within their use-by dates, we have no worries about explosive outcomes, if any. We keep spares in the house for all critical applications (we once went 9 days without power after Sandy, so this is no small thing.   Does it cost us a few bucks per year? Do we contribute some nasty chemicals to the waste stream - Yes and probably. But there is peace-of-mind.   Peter Wieck Melrose Park, PA

"pfjw@aol.com" <pfjw@aol.com>: Feb 07 01:17PM -0800 > Since tou mentioned thermocouples, I always wondered how they produce a > voltage. I've probably installed/replaced at least 10 of them, but never > understood how they work to create a voltage.....   They convert a small amount of the heat differential (hot end to cold end) into DC electricity. It is, mechanically, a bi-metallic strip inside the probe that converts the heat. They are quite elegant little devices, but, sadly, do not make much voltage (0.750V) at tiny, tiny currents. Just enough to trip a gas-valve. Certainly not enough to drive electronics on a thermostat.

Jerry Peters <jerry@example.invalid>: Feb 07 09:29PM > (I still think the best Thermostats made were those old round Honeywell > ones with the mercury switch. They lasted decades and never needed any > repairs. So much for so called "improved technology").   My programmable thermostat has an auxiliary thermoswitch that will turn on the furnace if the temperature goes below around 50F or so, even if the battery fails or the thermostat itself fails. It's a Robertshaw, about 20 or so years old. The thermoswitch is clearly visible on the baseplate assembly. The thermostat itself is removable from the baseplate so you don't have to stand at it when setting the program.   I'd expect most decent battery powered thermostats to have a similiar feature. Otherwise I could see lawsuits against the manufacterers or the heating contractors when the battery fails and the pipes freeze and cause extensive water damage.

Wayne Chirnside <wc@faux.com>: Feb 07 09:57PM On Tue, 07 Feb 2017 03:58:36 -0600, oldschool wrote:     >>> (I still think the best Thermostats made were those old round >>> Honeywell ones with the mercury switch. They lasted decades and never >>> needed any repairs. So much for so called "improved technology").   Have the same here. 24 volt transformer on the AC -furnace and the units either pass the 24 volt current or not to switch the relay on the furnace _ Ac depending on whether it's set on heat or cool. Relay on the AC - Furnace has a evaporator fan sequencer to keep the fan running for some minutes after heat or cool and prevent the AC compressor from restarting so soon as to damage the compressor.

etpm@whidbey.com: Feb 07 05:23PM -0800 On Tue, 7 Feb 2017 21:29:16 -0000 (UTC), Jerry Peters >feature. Otherwise I could see lawsuits against the manufacterers or >the heating contractors when the battery fails and the pipes freeze >and cause extensive water damage. I'm gonna check mine and see if it has the extra thermoswitch. If not I should wire one in. It is a great idea. A friend of mine had his house freeze while he was gone due to some sort of malfunction and a pipe burst inside the house. Water ran for over a week before the problem was discovered. The leak was quite small and still damaged a lot of stuff. Eric

Jon Elson <jmelson@wustl.edu>: Feb 07 05:35PM -0600 whit3rd wrote:   > makes a big difference, the old capacitor needs replacement.   > Look for a date on the capacitor (and if you replace it, write a date on > the new one); tracking the history sometimes simplifies things. I seriously doubt the run capacitor is anywhere NEAR 400 uF. It would be as big as a toaster in 1950 technology. Maybe 40 uF, but even that sounds big for a run cap.   Jon

etpm@whidbey.com: Feb 07 05:16PM -0800 On Tue, 07 Feb 2017 17:35:22 -0600, Jon Elson <jmelson@wustl.edu> wrote:   >big as a toaster in 1950 technology. Maybe 40 uF, but even that sounds big >for a run cap.   >Jon Greetings Jon, I have a box full of oil filled capacitors. They are all the oval shaped type and fairly modern. None are more than 50 mfd. I was getting suspicious of what I wrote and your post convinced me to take another look at the old cap in the motor base. You are correct of course, 470 mfd would have been bigger than the grinder. Maybe bigger than ten grinders.The cap is 4.0 mfd. What I took to be the number 7 was just corrosion on the old can. How could I have expected the old cap to be 470 mfd? What was I thinking? Just goes to show,, "If you can't think too good you shouldn't think too much". Thanks, Eric

"Benderthe.evilrobot" <Benderthe.evilrobot@virginmedia.com>: Feb 07 09:19PM "Phil Allison" <pallison49@gmail.com> wrote in message news:e5a4594d-8ec4-47ad-829c-77384141d829@googlegroups.com...   > ** But the OP claims he has TWO sets on the same antenna - one of which is > 100% OK.   > That's gotta be a set fault.   Maybe corrupted data on a user settings EEPROM.   Or if the affected channels are on a different band, they could be on a second tuner that could have died.

"Benderthe.evilrobot" <Benderthe.evilrobot@virginmedia.com>: Feb 07 09:12PM "N_Cook" <diverse@tcp.co.uk> wrote in message news:o7c5lr$c40$1@dont-email.me... > And of course buried deep in the case surrounded by all sorts, that block > access, to grind flat blade slots in the screw heads or pairs of flats for > mole-grips etc.   Might be worth reading the; "Best Philips screwdriver" thread.   Could be the crosspoint in the screw head is too shallow for the pointy end of your screwdriver and the cross blades are only part engaging.   Screws can be tight, and a poor fit screwdriver will ruin the head.   Unless there's an overhead obstruction, you should be able to seat a drill bit in the crosspoint recess and drill the head off. Removing the threaded bit with only the thickness of the PCB to get hold of might be fun.   If you haven't chewed the heads up too much, drilling down with a pilot drill smaller than the thread core diameter might allow you to turn it with a regular Philips screwdriver. Or you could graze the pointy end of the screwdriver a little with a grinder.

clare@snyder.on.ca: Feb 07 02:22PM -0500 On Mon, 06 Feb 2017 21:54:54 -0800, Spare Change   ><https://en.wikipedia.org/wiki/Glowing_plate#Common_Occurrences>   >Several causes listed are caused by shorted or leaking capacitors. It's a >tube killer. A;so the sinle largest killer of hard to replace power transformers.

"Benderthe.evilrobot" <Benderthe.evilrobot@virginmedia.com>: Feb 07 07:59PM <clare@snyder.on.ca> wrote in message news:th7k9cl63nqp5gaql8pfsfp6nu7dpvuoss@4ax.com...   >>Several causes listed are caused by shorted or leaking capacitors. It's a >>tube killer. > A;so the sinle largest killer of hard to replace power transformers.   Not to mention a leaky grid coupling cap can pass a large DC voltage from the plate of the previous stage. I've seen tubes that got so hot the glass melted and the vacuum wrapped it round the internal structure like cling film.   If it happens in Ham gear - the PA tubes are seriously expensive.

oldschool@tubes.com: Feb 07 02:57PM -0600 >>Several causes listed are caused by shorted or leaking capacitors. It's a >>tube killer. > A;so the sinle largest killer of hard to replace power transformers.   I have put fuses on the secondaries of the power transformer on some high powered amplifiers. (On the high voltage leads). That protects the xformer as well as other parts. Line fuses on the primary are not enough in my opinion.

Michael Black <et472@ncf.ca>: Feb 07 04:11PM -0500

Klaus Bahner <Klaus.Bahner@ieee.org>: Feb 07 09:39PM +0100 On 06-02-2017 21:25, Spare Change wrote: > BZW6-26, 26v TVS unidirectional diode, through-hole, obsolete, n/a.   It's not shown as obsolete by Diotec. They claim distributor stock of several thousand in PL, DE and SK.     > http://diotec.com/tl_files/diotec/files/pdf/datasheets/bzw065v8   > All replacements I see, the surge current is nowhere near 100A or is spec'd > at 10/1000 uS waveform.   P6KE-30A from ST is a direct replacement, with exactly the same specifications.     Klaus

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