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Cursitor Doom <curd@notformail.com>: Mar 09 05:48PM On Wed, 09 Mar 2016 00:20:35 +0100, Dimitrij Klingbeil wrote:   > There's no need to unsolder, neither to actively avoid unsoldering. That > resistor is connected through a diode on the board. Just apply the > proper polarity signal, and the diode will take care of the isolation.     Hi Dimitrij, Actually I did unsolder it in the the end as I wanted to inspect the underside for any clues as its specifications. Sadly there were none visible all around the device. Clearly all was not well with it and I'm inclined to believe that it's not an original part; just another poor replacement. When I removed it from circuit I was happy to give it 2W worth of power and see what happened. It just got hotter and hotter until I had to pull the plug at 120'C because my probe won't go any higher. In contrast, a known good 20ohm 2W resistor fed with the same 6.3V rose to 70'C and stopped at that. I have now replaced the old brown 'thing' with a 6W ceramic power resistor which after half an hour of running hooked up to the scope and under load only gets up to 40'C which I'm entirely happy with. The transformer is making a nice gentle, barely audible hiss; not that rasping sound it used to before your diode was replaced; all the DC Vouts are fine and there's no acrid scorching smell coming from the board any more; just a pleasant warm 'smell' of electronics behaving themselves. :) I now feel confident enough to re-insert the board and connect up the VHT and EHT and heater supplies - then we'll see if there's any life in the tube! But that will have to wait until tomorrow or I'm looking at divorce again, apparently. :( Later....

legg <legg@nospam.magma.ca>: Mar 09 04:16PM -0500 On Wed, 9 Mar 2016 17:48:50 -0000 (UTC), Cursitor Doom >tube! But that will have to wait until tomorrow or I'm looking at divorce >again, apparently. :( >Later....   From previous traffic on this issue:   "If these are the maroon-colored parts, they are Philips flame-proof parts designed to run with body surface temperatures in excess of 175C.   "The long preformed leads are thin dia steel, with poor thermal conductivity, in order to reduce thermal conduction to the printed wiring.   "Your real concern should be the temperature of film caps and insulators in the immediate viscinity, which have a lower tolerance to overtemperatures. They should not touch.   "Book hot spot limits for Philips PR01, PR02 and PR03 is between 220 and 250C, depending on the series. This is typical for later metal glaze films. Book derating for normal use is linear, to zero watts at 150C ambient."   Larger bodied resistors with the same power ratings may run at a lower body surface temperature, but this will be of little value if their bulk results in reduced air flow or physical contact with nearby components.   This position should not be filled with a wire-wound component. Metal glaze, at certain values and body sizes, offers a reduced self inductance, allowing them to function in higher frequency snubber circuitry.   RL

Cursitor Doom <curd@notformail.com>: Mar 09 10:37PM On Wed, 09 Mar 2016 16:16:19 -0500, legg wrote:   > From previous traffic on this issue:   > "If these are the maroon-colored parts, they are Philips flame-proof > parts designed to run with body surface temperatures in excess of 175C.   So you're saying these ARE the original factory parts? Wow!     > "Your real concern should be the temperature of film caps and insulators > in the immediate viscinity, which have a lower tolerance to > overtemperatures. They should not touch.   I think I can now see how that first diode met its end. Having its own radiant 1 bar fire juxtaposed to it would have lowered its junction barrier height - we all remember how temperature affects p-n junctions - enabling increased current flow and the eventual destruction of the diode through thermal runaway. It was asking for trouble having that resistor running at such a high temperature in this particular position.   BTW, there's an identically-sized power resistor at right angles to the one I've now binned and after a half hour's running, it tops out at only 33'C. I know it's got different working conditions, but in this case it was correctly rated for its job - unlike the other one. Looks like a design error after all, then.   > Larger bodied resistors with the same power ratings may run at a lower > body surface temperature, but this will be of little value if their bulk > results in reduced air flow or physical contact with nearby components.   Not a problem with the new component.   > Metal glaze, at certain values and body sizes, offers a reduced self > inductance, allowing them to function in higher frequency snubber > circuitry.   Yes, I'm aware of the perils of parasitic inductance in w/w resistors; the one I've selected doesn't suffer from it.   Be nice to see some traces tomorrow (one can but hope!)

Dimitrij Klingbeil <nospam@no-address.com>: Mar 09 11:57PM +0100 On 09.03.2016 18:48, Cursitor Doom wrote: > your diode was replaced; all the DC Vouts are fine and there's no > acrid scorching smell coming from the board any more; just a pleasant > warm 'smell' of electronics behaving themselves. :)   Hi   Looks like you've got it going back to normal operation, finally!   The whole thing might just have been victim of a resistor with a "hot channel" (old carbon resistors will sometimes do this without reason).   Or an improperly replaced one - likely the same result. No matter if it broke down with a low resistance path or if it got replaced improperly.   You can check if that was the case (if you still kept the resistor) by hooking it up to a power supply with an ammeter. If you see it heat up and then suddenly the amperage rising and the resistor starting to heat even faster (as if that was an NTC in there) then it very likely has developed a hot channel (a small area not quite unlike an arc path that conducts lots of current as it overheats).   If that's the case, it may explain several things. For once, this resistor was intended to provide a field reset function for the inductor. The circuit would likely require the reset to be quite "complete" (the field decaying to zero) between switching cycles.   If the resistance is lower than normal, the field will decay slower, and a resistor with a hot channel would likely slow the winding reset long enough to be "incomplete" - that is, by the time that the next switching cycle arrives, there would be still significant remaining current flowing through the inductor and the diode.   This can be a condition that the power circuit might not like. There is only a moderately fast diode in there - the original BY208 is not really fast. As long as the winding reset is complete, that might not matter because the diode would already be "out of charge carriers" when the next pulse arrives, so there would not be much reverse recovery.   If the reset happens to be incomplete because of the resistor breaking down, then the diode would still be conducting when the pulse comes and that would bring its (quite long) reverse recovery time into equation. During that reverse recovery time the diode would pass current and the resistor (and subsequent circuitry too, up to the resonance LC) would be getting "hammered" with large 800 V voltage spikes from the switcher, thus it would be subjected to high peak currents because of the spikes.   Of course, hammering the resistor with enormous voltage spikes won't be very good for its reliability, and since it was already breaking down, would also accelerate the process a lot (and stress other parts too).   Dimitrij

legg <legg@nospam.magma.ca>: Mar 09 06:31PM -0500 On Wed, 9 Mar 2016 22:37:40 -0000 (UTC), Cursitor Doom   >On Wed, 09 Mar 2016 16:16:19 -0500, legg wrote: <snip> >> circuitry.   >Yes, I'm aware of the perils of parasitic inductance in w/w resistors; >the one I've selected doesn't suffer from it.   Unless you've actually cracked one open, you will not be able to tell what the element construction is.   RL

Cursitor Doom <curd@notformail.com>: Mar 09 11:37PM On Wed, 09 Mar 2016 18:31:44 -0500, legg wrote:   > Unless you've actually cracked one open, you will not be able to tell > what the element construction is.   No need. I have a VNA. Better than x-ray vision.

Cursitor Doom <curd@notformail.com>: Mar 10 12:04AM On Wed, 09 Mar 2016 23:57:37 +0100, Dimitrij Klingbeil wrote:   > Looks like you've got it going back to normal operation, finally!   I know! It just seems so weird having the thing running like a top for the first time, not having to worry about overheating, not having that horrible burning smell and the rasping noise - plus all the voltages where they should be. :) But I couldn't have done it without you, Dimitrij. I'm enormously grateful for your assistance and your lengthy explanations have been a huge help to me in getting to grips with this 'alien technology' LOL.   Anyway, it's late here now so I'll report back tomorrow for what will hopefully be the last time.

Julian Barnes <jb9889@notformail.com>: Mar 10 12:09AM On Thu, 10 Mar 2016 00:04:29 +0000, Cursitor Doom wrote:   > But I couldn't have done it without you, Dimitrij. I'm enormously > grateful for your assistance and your lengthy explanations have been a > huge help to me in getting to grips with this 'alien technology' LOL.     Amen to that. Been quietly following this from the start and have learned a lot. Dimitri, are you a professional SMPS designer by any chance? I admire your carefully-considered 'measure twice, cut once' approach.

JW <none@dev.null>: Mar 10 11:14AM -0500 On Wed, 9 Mar 2016 23:57:37 +0100 Dimitrij Klingbeil   >You can check if that was the case (if you still kept the resistor)   One thing I've learned the hard way. NEVER throw out any replaced components until the repair is done!

Cursitor Doom <curd@notformail.com>: Mar 10 04:15PM On Wed, 09 Mar 2016 23:57:37 +0100, Dimitrij Klingbeil wrote:   > Looks like you've got it going back to normal operation, finally!   Yes! I can confirm it is now back up and running and early checks don't seem to show any other faults. I've got four nice bright sharp traces and all the buttons and knobs seem to do what they should (although I haven't exhaustively tested *every* single function at this time, of course). The only error I made was switching it back on from 'cold' - it clearly hasn't been on for a long time and I really should have brought it back to life on a variac but I forgot. There were some initial crackling noises and whatnot but they gradually subsided; some noisy knobs obviously as only to be expected, requiring lubing up but nothing else noteworthy.   Many thanks again to all who assisted. The kids at the local school electronics club will soon have a new toy to add to their test gear. :)

Cursitor Doom <curd@notformail.com>: Mar 10 04:16PM On Thu, 10 Mar 2016 11:14:39 -0500, JW wrote:     >>You can check if that was the case (if you still kept the resistor)   > One thing I've learned the hard way. NEVER throw out any replaced > components until the repair is done!   Good advice, but it's all fixed now (see my other post of a moment ago).

"pfjw@aol.com" <pfjw@aol.com>: Mar 10 05:46AM -0800 This might be of interest to some. My neighbor down the block is restoring a 1969 GM pick-up truck, and brought me the vintage radio from it to see if I could do anything with it. He had *NO* interest in converting to FM, much less stereo, all he wanted was to get the AM back.   The radio looked like it had been ridden hard and put away wet each and every day since 1969, fully encrusted with filth, grease, what looked like melted sugar, plastic and more. To the point where the tuning knob was locked, as were the preset buttons. This is a solid-state radio, not tube, of course.   I took the attitude of kill or cure, so after partial dis-assembly, removing the top and knobs, I put it on the top shelf of the dishwasher (Bosch) and ran it through a full scrub cycle (alone), then dried it in the oven for 2 hours at 175F. It came out sparkling clean, and with (thankfully) the back-painted numbers on the dial intact.   NOTE: Do not try this with dishwashers that have exposed heating/drying elements. They get too hot in some cases.   Applied power and got hiss. Check the 4-section cap, ESR was good, but by resistance, two of the internal sections were shorted such that capacitance was high, but they were, effectively, the same cap. I replaced the entirety with new caps rated slightly higher in capacitance, twice the voltage.   Applied power into a very inefficient speakers and got HUMMM - under a fluorescent shop light.   Installed an antenna - got reception across the band. This is the 6th bit of electronics I have put through the dishwasher. Two Zenith TransOceanics, one Dynaco FM5 tuner, one Dynaco PAT4 pre-amp and one other US tuner. Haven't lost a patient yet.   Don't be afraid to take heroic measures if the alternative is landfill.   Peter Wieck Melrose Park, PA

John-Del <ohger1s@aol.com>: Mar 10 07:50AM -0800 > Don't be afraid to take heroic measures if the alternative is landfill.   > Peter Wieck > Melrose Park, PA   And here I thought that dishwashers were made for steaming fish..   Did you use standard dishwasher detergent or something else?

N_Cook <diverse@tcp.co.uk>: Mar 10 04:05PM > Don't be afraid to take heroic measures if the alternative is landfill.   > Peter Wieck > Melrose Park, PA   Was SWMBO around at the time?

mike <ham789@netzero.net>: Mar 09 11:23PM -0800 I have an Ungar 9911 soldering iron handpiece without the controller. Looks new.   I thought it would be trivial to build a temperature controller. I can make it hot. There is some PTC going on as the current goes down as the iron heats up.   I expected some feedback. The only other connector pins that have some connectivity measure 497 ohms independently of temperature. Can't use that for temperature monitoring.   Google has failed me. Anybody know how these work?

N_Cook <diverse@tcp.co.uk>: Mar 10 12:22PM On 10/03/2016 07:23, mike wrote: > temperature. Can't use that for temperature monitoring.   > Google has failed me. > Anybody know how these work?   Any inductance with the 497R ? perhaps a small relay in the handle

Adrian Caspersz <email@here.invalid>: Mar 10 01:42PM On 10/03/16 07:23, mike wrote: > temperature. Can't use that for temperature monitoring.   > Google has failed me. > Anybody know how these work?   Probably it's a diode, and an auto-ranging DMM showing forward voltage not resistance.   e.g.   http://www.tmatlantic.com/upload/aktakom/AM-1142_Diode_Test.jpg   Try reversing the test leads?     -- Adrian C

N_Cook <diverse@tcp.co.uk>: Mar 10 02:03PM On 10/03/2016 13:42, Adrian Caspersz wrote:   > e.g.   > http://www.tmatlantic.com/upload/aktakom/AM-1142_Diode_Test.jpg   > Try reversing the test leads?   Diode would make an excellent temp sensor, but you would have it right at the duty end, for minimum time-lag, are there high-temperature diodes ? or a way to have a fast-response normal diode set in a thermal-conductance scaled-down insulated sub-housing?

N_Cook <diverse@tcp.co.uk>: Mar 10 02:10PM On 10/03/2016 14:03, N_Cook wrote: > at the duty end, for minimum time-lag, are there high-temperature diodes > ? or a way to have a fast-response normal diode set in a > thermal-conductance scaled-down insulated sub-housing?   Just got me thinking. Is there a soldering iron control system that uses an IR pyro sensor , set well back in the handle , in sight of but can monitor the heater block from afar?

Adrian Caspersz <email@here.invalid>: Mar 10 02:13PM On 10/03/16 14:03, N_Cook wrote: > at the duty end, for minimum time-lag, are there high-temperature diodes > ? or a way to have a fast-response normal diode set in a > thermal-conductance scaled-down insulated sub-housing?   Yes, I started thinking that after posting. Who knows?   -- Adrian C

N_Cook <diverse@tcp.co.uk>: Mar 10 02:16PM The problem with soldering iron control is putting a temp sensor in the heater block , if you can get away with simple heater and replaceable tips only, keeps the costs down (and swapping-out universality up , for hacker types). Ah so no manufacturer would want that. Another thing to try out sometime as a proving exercise.

"Ralph Mowery" <rmowery28146@earthlink.net>: Mar 10 10:43AM -0500 "mike" <ham789@netzero.net> wrote in message news:nbr79p$dis$1@dont-email.me... > temperature. Can't use that for temperature monitoring.   > Google has failed me. > Anybody know how these work?     After a quick search here is some info I found. Seems that there is no feedback for the iron.   On 3/25/2013 10:58 AM, Wild_Bill wrote:

"David" <David@nospam.please>: Mar 10 07:14AM "DaveC" wrote in message news:0001HW.1C8B4B670002EE5111CD2E3CF@news.eternal-september.org...   Cleaning up an old rotary mode switch used for 5v logic levels. It has some kind of grease in it.     …which has always confused me: grease is an insulator (well, the grease in this switch is—just tested and it's infinite ohms).   I read that dielectric grease is good to keep contacts sealed against the elements that have high physical pressure (which overcomes any separation provided by the grease) but that signal and other low voltages grease is contra-indicated.     =========================================================================   Here in the UK, Electrolube manufactures a contact grease   http://www.ebay.co.uk/itm/like/111883046769   Electrolube has been selling this for 60+ years   Hope this helps

whit3rd <whit3rd@gmail.com>: Mar 09 12:24PM -0800 If you can, charge the battery and try with the AC disconnected. The symptoms you describe can be caused by a noisy power source (which resets the machine and causes multiple startup cycles, then interrupts them).   The battery (different power source) might not work better, but it's worth a try.

Jeff Liebermann <jeffl@cruzio.com>: Mar 09 06:18PM -0800 On Tue, 8 Mar 2016 23:12:43 -0800 (PST), janetnkansah1@gmail.com wrote:     > My Toshiba laptop Statellite C855-S5356,   Hmmm... about 4 years old: <https://www.google.com/search?q=laptop+toshiba+satellite+c855-s5356&tbm=isch>   > When switched on boots up to the bios stage then the screen will > change to some multi-checker boxes (as if using a scratched DVD > in a DVD player)   That's a failure to initialize video RAM which is shared with the main memory. The light show on the screen and the boot failures indicate some kind of RAM failure. As "Ken" suggested, try removing the RAM, cleaning out any dust and debris, and CAREFULLY reinserting it. If that doesn't fix it, try one DDR3 RAM stick at a time. If one is bad, it will be obvious. If you have new RAM   Go thee unto: <http://www.memtest.org> or <http://www.memtest86.com> and burn a CD or flash drive with their memory testing programs. If you're lucky, it will boot and you can test your CPU, RAM, buses, etc.   If that doesn't work, leave the RAM in place, but unplug literally everything that can be removed. Remove the CD/DVD drive, wi-fi card, hard disk, and any USB dongles. One of them might be hanging the bus.   There's also a small chance that the battery might be causing a problem. Try removing the battery and running it totally on the charger.   On the other foot, it might be a bad GPU BGA chip to motherboard soldering job, which will take a major effort to reflow. <https://www.youtube.com/watch?v=cP2QOXNMA9g> Use an aluminum foil heat shield to avoid frying the PCB.       -- 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

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