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N_Cook <diverse@tcp.co.uk>: Nov 29 11:49AM Put in replacements and fan and sp relay came on , then a bang and loads of smoke. 680nF 400 V black cap in series with large toroid inductor, split open, I'd not noticed the bulge from in-use heating previously. Seems to be across the sp line also. Replaced that and running wiht no hotspots and amplifying perfectly happily. That L-C filter and amp being 2x power Darlingtons it would seem (under those sprung clips , you have to prize all 8 of them back with stirrups and remove the h/s, to see the idents though). A lot of differences to the 1 known Mark Bass schematic out there, marked CMD 102P , as they often seem to be, M3003 is leading digits of the S/N if the model type is encoded in that. Anyway putting a scope on the sp output, there is a constant <>200KHz 1.5V "modulated" on the audio, nothing of that heard on speaker of course . Not present on either +/-80V lines. The first thing to try is de-looming the unscreened ribbon connections that go across 2mm from the inverter, with rear send/rec lines to prea go right over the top of the SMPS Tx. Not investigated S/R bypasses, if opening, then possible more switching noise is injected then. So reloom with extra sleeving away from the Tx looks possible. Going by the rest of these amps that loom path was probably "designed" to go on the worst possible routing. Failing that , what else to look for. ? I'm assuming that 1.5V 200 KHz flares up at times in-use. No idea how much in-use local heating around the Zobel before the relay got jammed closed (so owner noticed bangs and whoops at sw on/off) ,but about 300 hours of use since the relay jam until final overheating

N_Cook <diverse@tcp.co.uk>: Nov 29 12:32PM for previous black cap -> internally blackened yellow cap   Repositioned that loom and no change. Did not think previously about disconnecting the PREA, but doing so and the same level of 200KHz on the zero audio out. OK unterminated input to the PA but why is this bass PA amplifying 200KHz anyway. No schematic , so looks like a small cap going in before the assumed Darlingtons (no predriver size transistors and cold DVM-D would suggest Darlingtons).

N_Cook <diverse@tcp.co.uk>: Nov 29 03:42PM So this amp is class D and that L-C filter should remove the 200KHz switching modulation, but is 1.5 pk-pk acceptable, time to visit s.e.d I think. Uses Si8244BB soic, at least there is full data on that, PWM input to that and so presumably driving a pair of powerFETs under the h/s clips , not Darlingtons

february30@nonewhere.com: Nov 29 06:11AM -0600 My old tube tester confirmed a short in this 6AU6 tube, which explains why a resistor fried on it's socket. I know replacement is the best solution, but old tubes are getting hard to find. I always figured shorts inside tubes occur because the parts inside are loose. Is it possible to drill into the glass, and use a pin to align the parts so they are not shorted, then shoot some epoxy inside to keep these parts solid, so they cant touch anymore?   Yes, I know they need a vacuum, so I'll have to use a vacuum cleaner to suck out the air, then epoxy the hole shut.

dansabrservices@yahoo.com: Nov 29 04:18AM -0800 > solid, so they cant touch anymore?   > Yes, I know they need a vacuum, so I'll have to use a vacuum cleaner to > suck out the air, then epoxy the hole shut.   The short answer is NO. 6UA6 tubes are still available in the marketplace.   Dan

N_Cook <diverse@tcp.co.uk>: Nov 29 12:42PM > solid, so they cant touch anymore?   > Yes, I know they need a vacuum, so I'll have to use a vacuum cleaner to > suck out the air, then epoxy the hole shut.   Have you got a source of caesium for the getter? C/H "shorts" you can often get a bit more life without "bacon & eggs" by upping the heater volts on the tester for a few seconds, to compress the oxide? back a bit. G/A shorts presumably due to thermal bending/failed spot weld unlikely. If I was going to give it a go I'd try very high magnetic field and high current through the G/A contact and arrange for the magnetic force to hopefully bend the relevant bit farther away. So shit or bust, make a G/A spot-weld or spring apart. If a structural suport failure , reorientate the valve perhaps

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>: Nov 29 09:47AM -0500 On 11/29/2016 07:42 AM, N_Cook wrote: > the magnetic force to hopefully bend the relevant bit farther away. So > shit or bust, make a G/A spot-weld or spring apart. > If a structural suport failure , reorientate the valve perhaps   Aren't the getters usually calcium? Caesium has a high vapour pressure--it's used in photomultipliers, and its migration is inconveniently fast even at 20C.   Cheers   Phil Hobbs   -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics   160 North State Road #203 Briarcliff Manor NY 10510   hobbs at electrooptical dot net http://electrooptical.net

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>: Nov 29 09:49AM -0500 >> suck out the air, then epoxy the hole shut.   > The short answer is NO. 6UA6 tubes are still available in the marketplace.   > Dan   There's a very interesting video tour of Mullard's Blackburn Valve Factory that explains a lot of stuff like that:   https://www.youtube.com/watch?v=GDvF89Bh27Y   Cheers   Phil Hobbs

ohger1s@gmail.com: Nov 29 07:12AM -0800 > solid, so they cant touch anymore?   > Yes, I know they need a vacuum, so I'll have to use a vacuum cleaner to > suck out the air, then epoxy the hole shut.   Before I was forced to try something that drastic I'd redesign it for a transistor. Here is an ebay listing for an NOS tube for $4 including shipping. He has four of them if you want to forestall drilling into your tube for a few decades...   http://www.ebay.com/itm/Philco-6AU6A-Electronic-Vacuum-Tube-Made-In-USA-NOS-/262736599165?hash=item3d2c52587d:g:53YAAOSwal5YEXx7

"pfjw@aol.com" <pfjw@aol.com>: Nov 29 07:18AM -0800 >>MUCH Snippage<<   a) Nothing you have 'at home' will create sufficient vacuum for what you propose. b) Even if you have a source of Barium to replace the original 'getter', you would have to remove the envelope entirely to install it. c) 6AU6 tubes are common, very common. I have at least a dozen in my tube stash. Our club sells them tested and good in the $2 range. d) And the chances are very likely unless you are a micro-surgeon, that you will screw something up in the process anyway.   Peter Wieck Melrose Park, PA

Jeff Liebermann <jeffl@cruzio.com>: Nov 28 10:14AM -0800 On Mon, 28 Nov 2016 04:05:54 -0000 (UTC), Raymond Spruance III >You had me scared, Jeff, when you flipped the coordinate system on me.   My proof reader and copy editor both missed my mistake.   >educumated when I next write back. >Celestial Navigation in a Teacup, by Rodger E. Farley >http://www.teacupnavigation.net/Celestial_Navigation_in_a_Teacup_v.pdf   Looks quite good from a quick skim.   The book assumes a working knowledge of geometry and trigonometry which might be suitable for a high skool level class. I think her biggest problem will be adding about 30 navigational terms to the students vocabulary. A navigation glossary might be useful. For example: <http://www.diy-wood-boat.com/Navigation_terms.html>   >The goal is to give the math teacher a lesson for her high school kids, >using freeware, where most are on iOS but some are on Android.   Like I suggested. Lose the apps and computah programs initially. Those can come later. Learn navigation with tables, paper, pen, calculator, slide rule, etc. I don't know if they're going to be plotting a course, but plotting sheets might be useful. Once you make it past the geometry and basic concepts, the rest is just math. However, my guess(tm) is that the teacher will become bogged down in the terminology and geometry. Due to lack of time, she will not get very far into practical navigation. At best probably a demonstration.   One problem is getting students a sextant for practice. Even the cheapest plastic sextant (Davis 3) is $50. Make their own sextant, octant, or quadrant? <http://www.tecepe.com.br/nav/CDSextantProject.htm> <http://www.science-teachers.com/space/north_star/HowtoMakeaSextant.doc> <http://www.tecepe.com.br/nav/XTantProject.htm> Make sure it has eye protection. I first learned navigation in a class of about 25 aspiring nautical types. Most brought their own sextants of varying quality. We took turns practicing sun sights with everyone using those numbers. I would not expect a high skool student to buy a sextant.   Good luck. -- 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

Whiskers <catwheezel@operamail.com>: Nov 28 06:49PM >> and HO229 sight reduction tables or this years nautical almanac.   > Really on the accurate clock? C'mon. I'll bet a five-dollar digital watch > has better accuracy than all the navigators had in the age of exploration.   Not many quartz watches qualify as 'chronometers' for navigation purposes. Best practice on ships is to have more than one chronometer on board, and know the 'rate' of each (ie how much it gains or loses each day, usually established by an observatory), and have them wound up and cared for by a designated officer and no-one else. These are used to maintain the accuracy of the watches actually used for observations.   But in an emergency, yes, any reliable watch is better than nothing. As long as the battery doesn't fail.   >> altitude correction).   > Can a plastic protractor substitute for a sextant for our purposes? > (i.e., it's more the process than the accuracy that I'm after.)   Consider at least looking at information about the 'astrolabe'; also later developments such as the 'quadrant' and 'back-staff' which preceded the 'sextant', all of which are within the scope of 'handicraft' or 'model-makers' to make (albeit not as accurately as a skilled instrument maker, but a lot cheaper!). I've even used a cardboard astrolabe to get fairly accurate time and latitude measurements. Once you've used an astrolabe, it's easier to grasp what a modern sextant is doing.   As well as maths and so on, this brings in history and culture and geography - and even literature (Chaucer wrote a little treatise on the astrolabe to instruct his son).   > Can't the phone bubble meter work for an artificial horizon?   > Anyway, you are correct these are land sightings. > In mountains. Santa Cruz mountains.   Any horizontal reflecting surface will do, eg a lake or strategically placed bowl of water. The nifty gadget is convenient, not essential.   (Astrolabes and quadrants don't need any sort of horizon, they use gravity to establish the vertical plane).   [...]   -- -- ^^^^^^^^^^ -- Whiskers -- ~~~~~~~~~~

"pfjw@aol.com" <pfjw@aol.com>: Nov 28 01:07PM -0800 On Sunday, November 27, 2016 at 11:01:40 AM UTC-5, Raymond Spruance III wrote:   Is trolling again under a different alias.   Please let this one stay a small thread!   Peter Wieck Melrose Park, PA

Jeff Liebermann <jeffl@cruzio.com>: Nov 28 08:34PM -0800 On Mon, 28 Nov 2016 18:49:20 +0000, Whiskers   >Not many quartz watches qualify as 'chronometers' for navigation >purposes.   If it's certified by the COSC, then it's a chronometer: <https://en.wikipedia.org/wiki/COSC> Only a fairly small number of watches are certified.   The specs allow a mechanical clock a daily rate of -4/+6 sec/day = 2.5 minutes/month = 30 min/year.   However, a crystal controlled clock is only allowed +/-0.07 sec/day = 2.1 sec/month = 25.2 sec/year.   There are now better clocks that easily meet the COSC requirements: <http://www.leapsecond.com/pages/atomic-bill/> <https://www.kickstarter.com/projects/846511652/the-worlds-first-true-atomic-wristwatch-the-cesium> -- 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

The Real Bev <bashley101@gmail.com>: Nov 28 11:27PM -0800 On 11/28/2016 08:34 PM, Jeff Liebermann wrote:   > There are now better clocks that easily meet the COSC requirements: > <http://www.leapsecond.com/pages/atomic-bill/> > <https://www.kickstarter.com/projects/846511652/the-worlds-first-true-atomic-wristwatch-the-cesium>   In [possibly] 2008 we bought some Casio 'atomic' watches with solar batteries at Costco for ~$25 each plus tax. The same watches are generally available for >$100 now. Not only are they incredibly accurate due to receiving nightly hits from the atomic clock in [I believe] Boulder CO, the black plastic bands show no sign of wearing out, unlike the bands on previous Casio digital watches I've had.   There's nothing quite like owning a truly accurate timepiece :-)     -- Cheers, Bev "The fact that windows is one of the most popular ways to operate a computer means that evolution has made a general fuckup and our race is doomed." -- Anon.

Tim R <timothy42b@aol.com>: Nov 28 11:23AM -0800 On Tuesday, November 22, 2016 at 2:01:57 PM UTC-5, Adrian Caspersz wrote:   > >> What could be the reason? TIA for any suggestions.   > > Probably bad capacitors on the mommy board.   > Have they been told to stand in the corner?   No, no, no!

Tim R <timothy42b@aol.com>: Nov 28 11:24AM -0800 On Monday, November 28, 2016 at 2:23:55 PM UTC-5, Tim R wrote:   > > > Probably bad capacitors on the mommy board.   > > Have they been told to stand in the corner?   > No, no, no!   that will make it worse.   The capacitors are heat sensitive, and ........................

Tim R <timothy42b@aol.com>: Nov 28 11:25AM -0800 On Monday, November 28, 2016 at 2:24:33 PM UTC-5, Tim R wrote:   > > No, no, no!   > that will make it worse.   > The capacitors are heat sensitive, and ........................   The corner is 90 degrees!!!!!!!!!!!!!!!!!!

Adrian Caspersz <email@here.invalid>: Nov 28 09:10PM On 28/11/16 19:25, Tim R wrote:   >> that will make it worse.   >> The capacitors are heat sensitive, and ........................   > The corner is 90 degrees!!!!!!!!!!!!!!!!!!   Almost obtuse, that was ....   :)   -- Adrian C

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