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DaveC <not@home.cow>: Feb 28 09:14PM -0800 for refurbishing a tape deck, I need some belts. I googled a few places but nothing very inspiring (not a great selection).     Anybody have a source they like and use?   (If you're just going to Google, don't bother, I've already done that…)   Thanks!

Ken Layton <KLayton888@aol.com>: Feb 28 10:39PM -0800 On Sunday, February 28, 2016 at 9:14:46 PM UTC-8, DaveC wrote:   > (If you're just going to Google, don't bother, I've already done > that...)   > Thanks!   Russell Industries bought out the old Projector-Recorder Belt Corp several years ago and still carries the "PRB Line":   http://www.russellind.com/prbline/index.html   They should have your belts. Just give them a call.

N_Cook <diverse@tcp.co.uk>: Feb 29 08:42AM On 29/02/2016 06:39, Ken Layton wrote:   > Russell Industries bought out the old Projector-Recorder Belt Corp several years ago and still carries the "PRB Line":   > http://www.russellind.com/prbline/index.html   > They should have your belts. Just give them a call.   But do they say whether they are new belts or old stock (so half perished already)? The total absence of any supplier stating they had new belts made me move over to cutting my own belts , flat and square , from silicone rubber kitchen products, no returns yet from broken examples.

jurb6006@gmail.com: Feb 29 01:09AM -0800 Though I think overpriced like everything else, I had a good encounter with Adamsradio. adamsradio.com IIRC.   I did look around and it seems that all the belts we paid fifty cents from back in the day are now five bucks. AND MORE ! The flat belt for that capstan will be more than five bucks. Maybe twenty. (actually that belt affects the wow and flutter spec of the deck and should be as right as possible)   But I can attest to the quality. I would use them again, unless someone really really killed them on price, and mean alot less than half. It is more important to have quality belts when you are spending time to take the thing apart and change them.   In the old days we just bought belts in bulk. For VCRs n shit. Today, things are different.   There are other PRB line dealers out there and they are your best best bet. I just mentioned one. Price a bit high but a fast ship and everything was up to snuff, all I got to say. Other than that, I don't even remember where this outfit is.   I am not sure if MCM and all them still carry PRB line stuff. Seems like really few places carry anything like that these days.

Chuck <chuck@mydeja.net>: Feb 29 08:47AM -0600 >(If you're just going to Google, don't bother, I've already done >that…)   >Thanks!   A heads up about PRB belts. Back in the 90s some of their belts would double the wow and flutter of the mechanism. Had better luck with MCM belts.   --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus

"pfjw@aol.com" <pfjw@aol.com>: Feb 29 08:35AM -0800 On Monday, February 29, 2016 at 12:14:46 AM UTC-5, DaveC wrote: > for refurbishing a tape deck, I need some belts. I googled a few places but > nothing very inspiring (not a great selection).   I have had excellent luck making belts myself from fresh O-ring stock. Or, from O-ring suppliers. Where a 'weld' does not matter, from stock. Where it does, from a supplier. They come in about every size (circumference) and diameter from a millimeter or two to 20+mm in circumference, and diameters from 10mm to over a meter. And in enough materials to cover about any need.   One of many, many: http://www.oringsusa.com/   My local plumbing supply house has not let me down yet as far as that is concerned. Not also that O-rings often do a fine job even where flat belts may be OEM. If there is any sort of lip on the wheels, there is rarely a problem. Note that diameter does not matter where belts are concerned as long as the tension is sufficient for traction. The pulley sizes are all that matters. And new materials often have a much higher tension strength than OEM belts typically of neoprene or even basic buna rubber. So, thinner O-rings may be used ILO flat belts if clearances are critical. And, as we all know, buna-rubber is not good around electrical stuff...   Peter Wieck Melrose Park, PA

"Ian Field" <gangprobing.alien@ntlworld.com>: Feb 28 09:25PM Google didn't find much of interest.   Is there any resource of general tech info on laptop batteries?   Some I've opened have Arizona Microchip PIC on the PCB, some have BQ prefix charge control chips - those I can maybe find online.   Thanks for any help.

Jeff Liebermann <jeffl@cruzio.com>: Feb 28 05:59PM -0800 On Sun, 28 Feb 2016 21:25:04 -0000, "Ian Field"   >Google didn't find much of interest. >Is there any resource of general tech info on laptop batteries?   Usually there's quite a bit of info in the app notes for the various fuel gauge and controller chips.   This might be of interest: <https://media.blackhat.com/bh-us-11/Miller/BH_US_11_Miller_Battery_Firmware_Public_WP.pdf>   >Some I've opened have Arizona Microchip PIC on the PCB, some have BQ prefix >charge control chips - those I can maybe find online.   Just Microchip, not Az Microchip. <http://www.microchip.com/design-centers/battery-management>   -- 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

Dimitrij Klingbeil <nospam@no-address.com>: Feb 28 06:55PM +0100 On 28.02.2016 16:18, Cursitor Doom wrote: > need. BTW, your explanations are unusually clear and thorough, I've > noticed. If you don't already, you really should edit or author > technical manuals. It's an all- too rare talent nowadays.   Ok. Usually most people who ask here understand DC parameters well enough, but rarely get to consider impedance, phase angles and such.   As for the 800 V, that was mostly a guess. Basically I've taken 320 V of the storage capacitor, added to that another 300 V of the resonant circuit (when the power transistor is off and it's being swung in the other direction) plus the voltage rise from the winding reset from the primary of L1806 (which is actually unknown since I don't know the ratio between primary and secondary, the secondary being at 320 V), which I guessed to be somewhere in the 200 V ballpark.   That's 320 V + 300 V + 200 V = 820 V, likely even to be more because the 300 V may reach up to 320 and the 200 is only a guess and may likely end up higher than that, plus there may be some 50 V from L1804 adding up in the same polarity, so even a 900 V total won't be out of the question.   That would be consistent with the rating of the BU208 power transistor, which has a 1500 V absolute maximum collector rating when driven from a low-impedance base drive signal.   As for definitely testing the resonance caps: I'm somewhat at a loss.   First thing, you can measure the capacitance, that an obvious test. If the capacitance is wrong, they're can't be working properly.   But reduced current handling ability comes from an increase in ESR and in the dissipation factor. To measure them, you would need to run the cap at the intended target frequency (and preferably at a realistic voltage too).   LCR+ESR meters can measure the dissipation factor and ESR, but those intended for electrolytics will often measure only ESR and also may have trouble testing such small foil capacitors like 33 or 15 nF.   Also, I don't know the target numbers for ESR and dissipation here, so one would need to compare them against a known good pair somehow.   An other way I can think of, would be to run them at resonance with the transformer, and measure both frequency and "Q". But that's also not meaningful unless one has a known good reference value for Q.   I think that the most realistic test would be to sweep the resonant circuit with a signal generator and watch the waveform. If the resonance frequency looks right (in the 20 kHz ballpark) and a signal generator is able to drive it from a high 600 Ohm source impedance to a significant amplitude without much "sagging" (that is, the resonant circuit presents little load to the generator), it's probably OK.   Dimitrij

Dimitrij Klingbeil <nospam@no-address.com>: Feb 28 07:06PM +0100 On 28.02.2016 16:18, Cursitor Doom wrote: > of noise across that resistor but that was before I was informed of > the importance of hooking the supply up to a load, so the test was > probably invalid.   Also, even with a dummy load connected, the stray capacitance of an oscilloscope, when hanging off the loose end of a power circuit with some 800 to 900 V worth of HF on it, would probably cause so much undue capacitive loading that the power supply circuitry would hardly handle it. That may have been the reason why you just got noise (the overload from the hanging scope may have affected the over-current shutdown of the power supply controller). As I said, the proper way would be with an isolated high voltage differential probe (such a probe would present very little stray parasitics) or maybe with a well matched pair of (identically compensated) HV probes in subtract mode.   Dimitrij

Dimitrij Klingbeil <nospam@no-address.com>: Feb 28 07:23PM +0100 On 28.02.2016 19:06, Dimitrij Klingbeil wrote: > some 800 to 900 V worth of HF on it, would probably cause so much > undue capacitive loading that the power supply circuitry would hardly > handle it.   P.S. That voltage estimate has probably surprised you. Unless one looks at the circuit schematic and adds all the voltages from all the storage elements (inductors / capacitors), considering timing and phase, it may not be obvious that the thing was intended to run at such high voltage levels. But there's a reason why they used a 1500 V transistor in it.

Cursitor Doom <curd@notformail.com>: Feb 28 07:53PM On Sun, 28 Feb 2016 18:55:47 +0100, Dimitrij Klingbeil wrote:   [...] > able to drive it from a high 600 Ohm source impedance to a significant > amplitude without much "sagging" (that is, the resonant circuit presents > little load to the generator), it's probably OK.   Thanks again, Dimitrij. You're obviously an expert on the little understood world of resonant converters so when you say try this or that, I make a point of paying extra attention. I liked your theory on the resistor heating due to this supply running out of resonance as a result of component values changing over time; in fact I'm currently pinning my hopes on it. It's a pity I'm stuck here for a few more days with my revolting in-laws but it'll be the first thing I do on my return!   Somewhere I have a big old valve/tube capacitor tester capable of simulating realistic high voltage working conditions. It'd be interesting to know what kind of checks it's capable of performing if it's still in working order and if I can find it among the towering piles of obsolete test equipment I have here (a couple of million pounds worth of gear at new prices adjusted for inflation) I may possibly hook it up and give it a shot.   How about those 'Octopus' component testers? They subject the part under examination to sweeping test voltages over the expected working range and you look for any signs of breakdown on an oscilloscope in X=Y mode. I guess this method is about as good as it gets?

Cursitor Doom <curd@notformail.com>: Feb 28 09:31PM On Sun, 28 Feb 2016 19:06:38 +0100, Dimitrij Klingbeil wrote:   > some 800 to 900 V worth of HF on it, would probably cause so much undue > capacitive loading that the power supply circuitry would hardly handle > it.   Isn't this just another example of the unsatisfactory nature of this resonant converter design? If the thing is *that* fussy that a little bit of stray capacitance can catastrophically destabilise it, then AFAICS it's a fundamentally unreliable topology and it would be better to have used one of the non-resonant forms of converter. Unless there's some compelling reason I may be unaware of not to for oscilloscope power supplies, of course.

Cursitor Doom <curd@notformail.com>: Feb 28 09:33PM On Sun, 28 Feb 2016 19:23:20 +0100, Dimitrij Klingbeil wrote:   > elements (inductors / capacitors), considering timing and phase, it may > not be obvious that the thing was intended to run at such high voltage > levels. But there's a reason why they used a 1500 V transistor in it.   And yet C1804 is rated at 'only' 630V. Weird!

Dimitrij Klingbeil <nospam@no-address.com>: Feb 28 10:50PM +0100 On 28.02.2016 20:53, Cursitor Doom wrote: > currently pinning my hopes on it. It's a pity I'm stuck here for a > few more days with my revolting in-laws but it'll be the first thing > I do on my return!   Hi   Please don't rely in my advice too much. While I do design electronics, I'm very far from being an expert in this particular field. I've never actually designed a resonant power supply, unless you count one little 3W prototype based on a modified Royer / Baxandall structure.   It may be relatively easy to look at a ready-made schematic and try to guess various upper and lower limits based on parts and topology (like "signal X cannot be higher than Y volts, otherwise part Z breaks down" or "ratio of transformer X cannot be above or below A:B, otherwise the ratings of part Y would be exceeded"), but that's not expertise by any stretch of the definition. A lot may be intuition, but that's no expertise either.     > working range and you look for any signs of breakdown on an > oscilloscope in X=Y mode. I guess this method is about as good as it > gets?   I've had to look up, what an "Octopus component tester" is. Apparently a transformer with some provisions for routing the voltage and current signals of the load to an oscilloscope, making a simple AC curve tracer.   I don't think that you'll need one here. It can test for breakdown, but in your case that's unlikely (the capacitor would be buzzing and arcing and the supply sure wouldn't work "almost normally"). It won't see the problems that are likely to be important in an LC circuit.   1. The cap must have the correct capacitance. Any LCR meter or any common pocket multimeter with a capacitance function can measure this. This is a basic prerequisite that should always be tested first and if the capacitance is wrong, no further tests will be necessary anyway.   2. The foils inside the cap must have a reliable connection (deviation manifests itself as ESR, ESL, and the general inability to supply high impulse currents). This particular curse will sometimes plague the trigger capacitors from photoflash units (the flash won't trigger or will only trigger erratically while the capacitance value is still ok).   This is difficult to measure directly, but can be checked with another capacitor as a reference. You'll need a known good capacitor with the same value (in your case: 15 nF), but not necessarily with the same voltage (you can use a known good, but lower voltage one for testing). The test is only with a signal generator, so the cap won't be subject to a lot of stress.   Connect the known good capacitor to the original inductor (transformer primary) with no other loads attached. Sweep with a signal generator (use as much voltage as the signal generator can provide without much distortion, that usually won't be a very high voltage anyway) and look for resonance on a scope. Note the resonance frequency. Disconnect the known good cap and connect the original one instead. Check where the resonance is. If it's in the same place and the amplitude has not become lower, the cap is very likely good. If it disappears and you can only measure the inductor's SRF instead, (if the inductor has more or less the same resonance with or without a capacitor connected), then the capacitor is basically open-circuit or very high ESR. If the resonance has wandered away somewhere, especially upwards in frequency, then the cap is most likely degraded and not a good candidate for full power resonant use either. Same thing if the amplitude has dropped much.   If your resonant caps turn out to be good, that most likely leaves only the snubber diodes and a possible frequency misadjustment as the likely causes.   If you check the resonance with a signal generator and scope against a known good 15 nF, and it suddenly wanders way, or the amplitude drops, then you'll need to find replacement capacitors. Fortunately, if you put "WIMA FKP1 33nF" into ebay search, there seem to be many available.   Regards Dimitrij

Dimitrij Klingbeil <nospam@no-address.com>: Feb 28 10:59PM +0100 On 28.02.2016 22:31, Cursitor Doom wrote: > better to have used one of the non-resonant forms of converter. > Unless there's some compelling reason I may be unaware of not to for > oscilloscope power supplies, of course.   That's definitely not "a little bit". By very far, not!   Muscling around a scope chassis (not the probe tip, but the probe ground and the big scope chassis connected to it on the other end of the cable) from zero to some 800 V in several dozen microseconds is no small feat, much less doing that 20000 times a second repetitively.   Not many power supplies will do that on an internal node without running into major stability issues (unless you have a very small battery-operated "pocket" scope, sitting on a wooden table far away from any earthed metal, thereby being a "light" load).   The probe tip is not the issue, but the scope itself, hanging from the probe ground, that is.

jurb6006@gmail.com: Feb 28 02:02PM -0800 >"Hhmmm. As I've said before, I'm reluctant to replace that power >resistor >with anything higher rated. "   It is NOT higher rated. A 100 watt incandescent in that spot will limit the current even lower and there is less chance of blowing anything else.   I did not mean to suggest that you change your plan of troubleshooting, just that next time when it comes to a hot test, use the bulb. If something is still shorted you have a hell of alot more time to figure out what, rather than having overheat in seconds. When the light dims, you probably found the problem. the light goes down in resistance as all the filters charge and get almost to full voltage, once it does that it works without a net. Regular fuse and all that.   I consider a dim bulb tester a must for this type of work.

Dimitrij Klingbeil <nospam@no-address.com>: Feb 28 11:13PM +0100 On 28.02.2016 22:33, Cursitor Doom wrote: >> run at such high voltage levels. But there's a reason why they used >> a 1500 V transistor in it.   > And yet C1804 is rated at 'only' 630V. Weird!   That's not a problem. It only ever sees 320 V from the mains, plus any little remains of the mains surges that may come its way past C1802+3.   Even with surges and such, 450 V is likely the highest thing it will ever see, so a 630 V rating is a good and conservative one.   It won't ever see the 800 V. But the transistor V1806 (collector) will.   Basically, the input caps will "see" only normal rectified mains (320 V). The resonant caps will also see some 300 to 320 V, but because the sinewave resonance signal is bipolar, and one end is tied to the positive end of the input caps, there will be times (each half cycle) where the voltages will add and the result (referenced to the emitter) will reach some 600 - 620 V. At these same times during the cycle, L1806 will also be reset via V1811, and the reset voltage (some 200 V, also being in series) will also add to this, plus any little remains (50 V or less) from the L1804 circuit. So the collector of V1806 will "see" quite a lot of voltage when V1806 is in the "off" phase. But this high voltage only applies to the V1806 collector, not to the other parts / signals.   Dimitrij

Dimitrij Klingbeil <nospam@no-address.com>: Feb 28 11:34PM +0100 On 28.02.2016 22:59, Dimitrij Klingbeil wrote: > from any earthed metal, thereby being a "light" load).   > The probe tip is not the issue, but the scope itself, hanging from > the probe ground, that is.   P.S. Since you indicated that you have some background with radio...   Consider the collector of V1806 as a signal source. As a signal source that can basically drive a 800 V peak-to-peak square wave.   Consider the whole power supply board (including any cables and the isolation transformer or variac that you are using to feed it) as one half of a dipole antenna.   Consider the scope (the whole metal chassis) and the probe cable as the other half of the same dipole antenna.   Consider the two halves connected in the middle by the probe ground clip, at that overheating power resistor in the supply.   What you get, is a center-fed dipole, sitting on your table, and being driven with a 800 V peak to peak fast square wave. Not a light load.   An isolated high voltage differential probe would "separate the halves", so that the big (parasitic) dipole would no longer exist.   Regards Dimitrij

Cursitor Doom <curd@notformail.com>: Feb 28 11:33PM On Sun, 28 Feb 2016 22:50:19 +0100, Dimitrij Klingbeil wrote:   [...]   OK, Dimitrij, a *huge* quantity of info to digest here and in your other new postings on the subject and more detail than I can assimilate in a single sitting! Many thanks as ever; that will certainly be all I need to know for the time being. I'll get to work on the checks when I return to base after midweek. Laterz...

Cursitor Doom <curd@notformail.com>: Feb 28 11:35PM On Sun, 28 Feb 2016 14:02:33 -0800, jurb6006 wrote:   [...] > I consider a dim bulb tester a must for this type of work.   Ah, that makes much more sense now; many thanks for that clarification.

DaveC <not@home.cow>: Feb 28 02:11PM -0800 Sony TC-WR99ES (or any TC-WR series cassette tape deck).     I can find for-pay manuals. Are there any resources for free downloads? (tried eserviceinfo.com)   Thanks.

DaveC <not@home.cow>: Feb 28 02:24PM -0800 Found it on electrotanya.com   -=-=-=-

etpm@whidbey.com: Feb 28 01:04PM -0800 On Sat, 27 Feb 2016 03:08:39 +0000, Mike Tomlinson   >It's a nice little heater, very quiet and efficient, so worth a bit of >time.   >Thanks again. Nice as it is the efficiency is same as any other electric heater. All the power going into it becames heat in the room it's in. ERS

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Dimitrij Klingbeil <nospam@no-address.com>: Feb 28 03:01AM +0100 On 25.02.2016 16:51, Cursitor Doom wrote: > power resistor heating that's causing concern. If you think of > anything else, please leave your thoughts here. If not, I'll proceed > with your checks on my return. many thanks again.   Hi   Since you were planning to be away for a while, I was in no hurry to reply right away. I've seen your other post too, and obviously the transformer must be ok.   I think that, from the major power-carrying components point of view, your power supply is now "almost ok". The "power train" clearly works, otherwise you couldn't get correct output voltages under load.   But the fact that the power resistor still overheats, hints to some timing being slightly wrong. It can no longer be "completely" wrong, as was the case with the slow diode, but it's not yet "right" either.     1.   There is still the question with V1808. You said it looks ok, and it tested ok with a multimeter, but that's not really indicative of its true behavior under full load at high frequencies. If it has degraded for any reason ("lost its switching speed") then the resistor R1814 would be running at a higher load than normal. Not many times higher, but about double or triple. That would be somewhat consistent with your observation of it running too hot after a few minutes. You should now have (hopefully) a few spare UF4007s, so if in doubt, replace V1808.   If you find out that the replacement of V1808 makes a (little) change for the better (slightly lower load on R1814), then replace V1809 too. It would in this case be likely that those BY208-1000s have all degraded and became out-of-spec. They all have the same type and age.   Actually it's possible to test the condition of V1808 in circuit, without replacing it, but the test is tricky. You would need to see, on an oscilloscope, the voltage waveform across R1814. It should be basically a flat line, with short surge-like spikes at some 20 kHz intervals. All the pulses must be polarized in one direction only. The left-hand pin (on the schematic) of R1814 must be positive. There must be no spikes in the reverse direction. If there are any (the polarity would be alternating), then V1808 is degraded and no longer operable at full speed and needs replacement(, and so does V1809 likely as well).   Unfortunately this test is difficult, because you can't connect a scope ground to R1814! This is a very fast switching signal that runs at high power and reaches voltages of some 800 V in normal operation! Even if you disconnect both mains grounds and "float" both the scope AND the power supply, and even if you power both the scope AND the power supply from two SEPARATE isolation transformers in order to increase isolation and minimize the stray capacitance via mains, this test would still be very dangerous and I would definitely not advise trying. Using two scope channels in "subtract" mode might work, but only if you have two high voltage probes rated for 1 kV, and only if both probes are exactly identical and the compensation of both channels is precisely matched to each other (a rather unlikely condition that requires some effort to achieve). To be honest, to do this test properly, you would need an isolated high-voltage differential probe. Unless you have one, don't even bother trying, to replace the diode is easier and much safer.   Ok, so much for the other BY208s in snubber circuits. Replace and see.     2.   The other open question is that of the resonance capacitors (C1807 and C1808). As I noted in another post, they may be degraded and it may be difficult to test for this condition properly (LCR meter won't likely show the problem). Again, if you can get known good spares, they can easily be replaced, but the spares must be rated for resonant operation. "Typical" film capacitors are not designed for this use.   Foil capacitors with Polypropylene isolation rated for continuous resonant duty like the "FKP 1" type should work well here, and so may "MKP 4C" type too, to some extent, but only the 630 V DC rated ones, and only if two are used in series like in the original schematic ("MKP 4C" with lower ratings would hit its high frequency AC limits).   So, "FKP 1" rated at 400 V or 630 V DC (two 33 nF in series) or rated at 1000 V DC (one single 15 nF) or "MKP 4C" rated at 630 V DC (two 33 nF in series), would be feasible replacement candidates, but not many others due to the high loading requirement in resonant operation.   If yours turn out to be degraded, and you replace the 30 nF originals (now probably unobtainable) with 33 nF, you may need to re-adjust the resonance frequency somewhat.     3.   Also, the frequency adjustment may be slightly out of resonance (maybe the previous repairer has misadjusted it and component parameters can also drift over the years). Again, a misadjusted frequency, especially if it has been set too high rather than too low (compared to the true resonance frequency of the LC circuit) can cause the dissipation resistor to overheat (so a little low is better than a little high).   A resonant circuit driven too slow (below resonance), will pull reacive power (will have a power factor below unity), but the direction of the phase shift will be inductive. If driven a too fast (above resonance), it will appear capacitive instead. Please note that the square-to-sine conversion circuitry, especially the snubbers, will have lower stress from peak currents when driving an inductive load than when driving a capacitive load, so an inductive load is "easier" on them.   Please read the instructions in the service manual (I've also copied the relevant part in my other post), and also note that the service manual clearly advises to always adjust the frequency "from below" and never "from above" ("use 170 V mains, then set the trimmer to lowest possible frequency, and slowly raise it until the output voltage regulation can just be obtained, but no more than this"). So the designers from Philips must have preferred this design to run rather slightly below resonance than slightly above it, and they must have had good reasons to write the adjustment instructions in such a way, as to prevent an accidental "too high" frequency setting.   Note that any frequency adjustment should be done with the correct dummy load connected in order to avoid entering a "light-load" mode.   Regards Dimitrij

Dimitrij Klingbeil <nospam@no-address.com>: Feb 28 03:33PM +0100 On 27.02.2016 01:42, Cursitor Doom wrote:   > 60 12.7 6 0 -6 -12.7 -60   > So very close! Looks like the main transformer may be ok after all."   > Making progress! :)   Hi   Noted your progress :)   But could you please make a complete list of found faults and your replacements, and post it here:   I mean, you posted at the very beginning (long before finding the slow diode) that you've found and replaced some obviously defective parts, but I can't remember if you ever posted, exactly which ones they were.   Also, you have indicated other things that may impair reliability (like capacitors with pieces of film isolation flaking off), and again, you didn't seem to indicate the exact schematic part numbers.   As you may well know, to troubleshoot anything properly and reliably, and to be able to assess the likely chains of cause and effect, one needs to know the history of the repairs, as completely as possible, and also anything obviously (visually or otherwise) suspicious too.   Therefore please make some lists, and take particular care to make them complete, to leave nothing out, and to indicate each and every listed part's schematic part number (important, since others can't see your board and need the exact numbers to identify the parts in question).   - one list with all previous repairs that you have found: which parts were replaced in the past, as visible from manual solder joints, and where the replacements were of different type from the original, clearly indicate the exact types of replacements.   - one list with all of your repairs: which parts you found defective and what exact parts (exact type and manufacturer) you have replaced them with.   - one list with all parts that currently look suspicious or for whatever reason seem to be of questionable integrity.   It would be nice if you could make a printout of the schematic, and mark all those items in color (like for example yellow for previous repairs, circled twice if the repair was inexact, red for those you replaced, and blue for the suspicious ones), and then scan and post the color- annotated schematic somewhere for us to see.   To avoid "... and what else was there?" or "... and what about part XYZ?", please make sure that this annotation is really complete. Trying to get such information one question at a time can be frustrating.   Regards Dimitrij

Cursitor Doom <curd@notformail.com>: Feb 28 03:18PM On Sun, 28 Feb 2016 03:01:02 +0100, Dimitrij Klingbeil wrote:   > but about double or triple. That would be somewhat consistent with your > observation of it running too hot after a few minutes. You should now > have (hopefully) a few spare UF4007s, so if in doubt, replace V1808.   Yes, I bought 20 of those faster diodes to be on the safe side. :)     > Actually it's possible to test the condition of V1808 in circuit, > without replacing it, but the test is tricky. You would need to see, on > an oscilloscope, the voltage waveform across R1814.   [live power resistor procedure testing snipped]   Actually I did do this a while back without knowing the risks! As you can see, I survived to tell the tale. All I was seeing was about 30V of noise across that resistor but that was before I was informed of the importance of hooking the supply up to a load, so the test was probably invalid.   > Ok, so much for the other BY208s in snubber circuits. Replace and see.   Certainly can do that, yes.   > C1808). As I noted in another post, they may be degraded and it may be > difficult to test for this condition properly (LCR meter won't likely > show the problem).   Is there any way of *definitively* testing such a capacitor against all its possible failure modes? And I'd be interested to know where you get this figure of 800V you mention from?   > A resonant circuit driven too slow (below resonance), will pull reacive > power (will have a power factor below unity), but the direction of the > phase shift will be inductive.   Fortunately this is one aspect I pretty much totally understand. As an old-style radio ham of more decades than I care to recall, the concepts of resonance, reactance, impedance, power factor and phase shift are like second nature so please don't go to any trouble explaining the finer points in extreme detail; there's absolutely no need. BTW, your explanations are unusually clear and thorough, I've noticed. If you don't already, you really should edit or author technical manuals. It's an all- too rare talent nowadays.

Cursitor Doom <curd@notformail.com>: Feb 28 03:28PM On Sun, 28 Feb 2016 15:33:02 +0100, Dimitrij Klingbeil wrote:   > I mean, you posted at the very beginning (long before finding the slow > diode) that you've found and replaced some obviously defective parts, > but I can't remember if you ever posted, exactly which ones they were.   I think you may possibly be getting mixed up with a different repair here, Dimitrij. I do have some flaky capacitors to replace when I return and I'll note which ones I change for your information. As for what previous technicians may have done, I have no idea what if anything has been replaced - apart from that one obvious diode. I got absolutely no background information on this scope, it was given to me for nothing by some guy who was emigrating so its past will now always remain a mystery. It's a pity, because this obviously adds another set of unknowns into troubleshooting the thing, but it's just something I'll have to live with I guess. In all honesty, this repair is proving to be a 'baptism of fire' for me in the world of SMPSs of which I admit I know very little (yet a lot more than I did 3 months ago!) :)

N_Cook <diverse@tcp.co.uk>: Feb 28 11:26AM In hindsight it should have been obvious why no lead mode. There is an error on the Mesa schematic of Mesa Boogie 3 on Elektrotanya. The lead-switch should take the common LDR1 - 4 line, to ground and not directly shorting those 4 leds as in the diagram, doh!

jurb6006@gmail.com: Feb 27 02:19PM -0800 Just to let you know I just found this 3212 to have a bad transformer. It is a little different as it runs on 24 volts, but it is bad.   I finally hooked it up to all its loads and it let out a little smoke when excited by a power amp at 10 KHz. Couldn't see where the smoke came from so I had a rally good look and looked at the transformer. The outside insulation appears burnt, not too bad but bad enough I guess.   Thing is, this thing has no shorts in it. Being a self oscillator of course the bad transformer stops it, not enough feedback.   I know it is a different unit, but this proves the transformers can go bad. I'd've never thunkit. Like, flybacks in TVs went bad but they had 30 KV floating around in there. The highest supply on this one is 1,500 volts.   Anyway, just lettin' y'know that it is probably more of a possibility than I thought before. If you find out unequivocably that your trasnsformer is bad let us know and I will take that into consideration if buying another one that does not have basic operation.   I don't like dead scopes anyway, 'I like to see a trace before putting the money down, but this one got thrown in on a package deal type thing so it won't break the bank.

mroberds@att.net: Feb 27 05:56PM > En el artículo <naqubs$uaf$1@dont-email.me>, mroberds@att.net escribió:   >> Taking mine apart,   > You didn't have to go to that much trouble, but thank you.   I use it a lot in fan-only mode, so it was about ready for its annual dusting anyway. :)   > There's 4 ceramic cores with two heat levels selected by a switch > (heat level 1 = 2 cores operating, heat level 2 = 4 cores operating)   Same here.   >> The part I have looks like their "AUT-P" series (with the white >> plastic tab)   > That sounds like a resettable one.   It is. There is no user-resettable button; you just have to unplug the heater and let it cool off.   > The ceramic element is held in place in a hard plastic frame, so isn't > going to be allowed to get very hot.   Same here. On mine, the frame also extends back towards the intake to hold the fan motor and make a venturi/shroud for the fan blade.   Matt Roberds

Mike Tomlinson <mike@jasper.org.uk>: Feb 27 06:56PM >On mine, the frame also extends back towards the intake to >hold the fan motor and make a venturi/shroud for the fan blade.   Yes, same here. It's all one piece. The section holding the ceramic element is square, then there's a short cylinder to the fan housing which is square. The lot fixes to the back half of the enclosure with 4 screws.   I suspect this is pretty much a commodity part made in China and badged with OEM logos as required.   I've ordered the 95C switch, pretty sure that'll do the trick. Thanks again for your help, have a virtual pint on me :)   -- (\_/) (='.'=) Bunny says: Windows 10? Nein danke! (")_(")

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andrew@cucumber.demon.co.uk (Andrew Gabriel): Feb 27 11:20AM In article <sNGdnTReYdJz31fLnZ2dnUU7-I-dnZ2d@westnet.com.au>,   > I'll believe Aluminium or steel I must admit to only a little actual > experience. > Some Cable guy should give an actual answer.   Ordinary soldering can be used with iron - soldering iron bits are often copper core for thermal capacity and conduction, with iron plating which wets well with solder but doesn't oxidise/corrode as quickly as a bare copper bit does.   As you go to steel and then stainless steal, it gets harder to do. Stainless steal in particular is protected from corrosion by a very tough layer of chromium oxide (I don't know if it's possible to solder stainless steel at all).   Aluminium has a similar problem - a very tough layer of aluminum oxide which needs a suitable flux to strip through. However, it also needs a different solder alloy to wet it - it's a long time since I did it but ISTR using a solder alloy containing silver.   A secondary problem with soldering dissimilar metals is that any moisture risks causing galvantic action/corrosion of the join, and in the case of aluminium, this happens even between the aluminium and the solder used. Selecting a flux which can strip the aluminimum oxide well whilst not leaving any residue which eventually corrodes the join is a bit of a challenge.   -- Andrew Gabriel [email address is not usable -- followup in the newsgroup]

DecadentLinuxUserNumeroUno <DLU1@DecadentLinuxUser.org>: Feb 27 01:10PM On Sat, 27 Feb 2016 11:20:43 +0000, Andrew Gabriel wrote:   > As you go to steel and then stainless steal   Engineering schlip?

MJC <gravity@mjcoon.plus.com>: Feb 27 04:28PM In article <nas0qb$nod$1@dont-email.me>, andrew@cucumber.demon.co.uk says... > and the solder used. Selecting a flux which can strip the aluminimum > oxide well whilst not leaving any residue which eventually corrodes > the join is a bit of a challenge.   This reminded me that I once knew about "purple plague". There's an article about it in Wikipedia.   Mike.

Aleksandr Motsjonov <soswow@gmail.com>: Feb 26 09:59PM -0800 John-Del, I've looked a bit more. I found labels on back side. One of the inputs from FRC Board is "ON_BACK", and there is also "P_ON" both are zero V when turned off, and when I press power the both get up to 3.2V "EN" and "ADJ" that goes to power supply board are at GND level at all times. The backlight voltage shows 25.8 when turned off, and 32.3 when turned on. I don't have a oscilloscope to see what kinda of shape this signal is. I still don't understand how does power supply "decides" when to change backlight voltage if "EN" and "ADJ" don't seems to be changing at all ... or maybe I measuring wrong.

John-Del <ohger1s@aol.com>: Feb 27 03:59AM -0800 On Saturday, February 27, 2016 at 12:59:31 AM UTC-5, Aleksandr Motsjonov wrote: > "EN" and "ADJ" that goes to power supply board are at GND level at all times. > The backlight voltage shows 25.8 when turned off, and 32.3 when turned on. I don't have a oscilloscope to see what kinda of shape this signal is. > I still don't understand how does power supply "decides" when to change backlight voltage if "EN" and "ADJ" don't seems to be changing at all ... or maybe I measuring wrong.   First you need to determine if you have a floating ground on the LED strips. You can do a resistance check from the ground plane of the power supply or metal frame of TV to either side of the LED connector. If one side reads zero ohms, use the frame or ground screw for your LED voltage. If not, locate a large electrolytic near the LED output section. This will have a voltage rating of 100 to 450 volts and the neg side of the cap will make a good ground. There are several ways the LED voltage is varied on these. Sometimes they actually vary the DC output, other times they use a mosfet on the low side of the LED strips and modulate the gate to provide the proper voltage drop across the string. Your reading is odd. It clearly is changing voltage but there doesn't seem to be enough difference between off and on to go from LED cutoff to full bright, but I could be wrong on this.   To answer your other questions takes some more guessing (again, no SM). In standby, the SMPS will put out either 3.3 or 5v typically for the main. The P_ON command from the main turns on the other outputs of the SMPS, such as 9, 12, 24 as required for the rest of the circuitry. In some TVs, this also turns on the PFC circuit (if equipped). When the PFC turns on, you'll see a big bump of voltage on this cap. Other boards will use a command from the inverter drive IC to turn on the PFC (rare). Still others use the successful power up of one of the other secondary supplies to turn on the PFC.   Not all configurations use the adj and enable lines, particularly the real cheap TVS. Is your "EN" line also the "ON_BACK" line? You can try floating the adj line to see if the backlight voltage increases.   Most times if a TV's status LED reports a start when the button is pushed and successfully turns on the power supply, the main is OK (but not always :(. I've seen some Vizios that will turn on everything but the backlight because the PWM (brightness) is missing.   The secret to all of this is datasheets. If you can find the datasheets for the LED drive IC (and PFC if it's equipped with one) you can go a long way with the proper pin outs, typical voltages, sample circuits, and descriptions of signals the ICs use.

John-Del <ohger1s@aol.com>: Feb 27 04:05AM -0800 On Sunday, February 21, 2016 at 4:32:57 PM UTC-5, Aleksandr Motsjonov wrote: > OK. I see what you mean. But I have problem understand how does PFC or any other logic board would be able to control LED. > The only connection power board has with main board via these 6 pin connection. > The only interesting bits here are ON/OFF and ADJ. Not sure if any of these would control output of the LEDs power output on other side of the power board:   I see an 8 pin connector on the close up that has two commands. If that is the only connector then the LED section is turned on with the rest of the power supply. The adjust will adjust the brightness of it. Because the main and smps/inv seem to be made by two different companies, they label them differently but I believe the enable and on/off turn on both the power supply and LED drive. If both of those go high, odds are very high that you have a problem either in the smps or an open LED.

Aleksandr Motsjonov <soswow@gmail.com>: Feb 27 04:11AM -0800 Thank you mate. Will read it carefully and do my best! Here is couple more photos with overall picture, back of this central boards set (With connector from FRC pin out) https://goo.gl/photos/FHLZtEyEj3QCFGMu5

Julian Barnes <jb9889@notformail.com>: Feb 26 07:08PM hey guys,   I need to remove a sub-miniature audio transformer from a PCB. It should be a piece of cake and always has been in the past, but something's different about this one. At those odd times previously when I've done this, I've just used a soldering iron and a vacuum pump to melt the joints and suck off the solder. The pins are then free and the part almost drops off by itself. This one is not so simple, though. It's a double-layer board and the transformer is mounted directly on top of the traces that feed it. On the reverse side, I can see the end of the transformer's leads poking through just proud of where a pad would normally be, but in this case, there are no pads 'cos there are no traces; just tiny, isolated circles of solder around each lead-end. I guess I need to get at the actual solder joints proper on the top side, but the transformer is sat right on top of them making it totally impossible to even see the joints I need to get at! Whut gives here? Are these things deliberately designed to be unserviceable nowadays? Is that the idea? Bastard manufacturers want us to buy new stuff instead of fixing old? Sigh. Does anyone know a ruse to defeat this darstardly scam?

"tom" <tmiller11147@verizon.net>: Feb 26 02:29PM -0500 "Julian Barnes" <jb9889@notformail.com> wrote in message news:naq7rg$3c4$1@dont-email.me... > nowadays? Is that the idea? Bastard manufacturers want us to buy new > stuff instead of fixing old? > Sigh. Does anyone know a ruse to defeat this darstardly scam?   Hot air desoldering tool.   This one works nice:   http://www.ebay.com/itm/281501377815?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT   Consider adding ChipQuick to lower the melting point.   http://www.ebay.com/itm/CyberDoc-CHIP-Quik-Quick-DESOLDERING-REMOVAL-ALLOY-2ft-FOUR-4x-6-5-inch-STICKS-/141758972378?hash=item21017e41da:g:XGcAAOSwPgxVLEkM   And flux.

N_Cook <diverse@tcp.co.uk>: Feb 26 07:28PM On 26/02/2016 19:08, Julian Barnes wrote: > nowadays? Is that the idea? Bastard manufacturers want us to buy new > stuff instead of fixing old? > Sigh. Does anyone know a ruse to defeat this darstardly scam?   Diamond encrusted cutting wire?

Cursitor Doom <curd@notformail.com>: Feb 26 10:00PM On Fri, 26 Feb 2016 19:08:33 +0000, Julian Barnes wrote:   > Are these things deliberately designed > to be unserviceable nowadays?   Probably.     > Is that the idea? Bastard manufacturers > want us to buy new stuff instead of fixing old?   Surely.   > Sigh. Does anyone know a ruse to defeat this darstardly scam?   They're a PITA - IME at any rate. This is one of the better explanations on how to deal with them:   https://www.youtube.com/watch?v=Z38WsZFmq8E

Rheilly Phoull <rheilly@bigslong.com>: Feb 27 07:23AM +0800 On 27/02/2016 6:00 AM, Cursitor Doom wrote:   > They're a PITA - IME at any rate. This is one of the better explanations > on how to deal with them:   > https://www.youtube.com/watch?v=Z38WsZFmq8E   The power suction jobs take some beating :-)

N_Cook <diverse@tcp.co.uk>: Feb 27 09:43AM On 26/02/2016 19:28, N_Cook wrote: >> stuff instead of fixing old? >> Sigh. Does anyone know a ruse to defeat this darstardly scam?   > Diamond encrusted cutting wire?   If soldered rather than rf welded joints. A small length of tungsten wire from a smashed 40W mains lamp, crimped to thicker delivery wire. Varying current of a bench ps, find the current for dull red heat of the tungsten. Drape the tungsten wire over one of the pins , and a forcing blade/wedge in the gap while delivering heat to that pin and repeat?

N_Cook <diverse@tcp.co.uk>: Feb 26 04:46PM On 26/02/2016 16:16, Mike Tomlinson wrote: >> First with a soldering iron barrel , confirm by listening for a click >> over, then repeat with a thermometer, glass or pyro.   > It's open circuit, with a burnt spade terminal. Trust me, it's u/s.   But not the dome, hack into it and extract the dome. Now not constrained, you need to make sure it does not fly off , when it flips to the opposite state.

mroberds@att.net: Feb 27 01:32AM > https://en.wikipedia.org/wiki/File:Goldair_GCH200_ceramic_heater.jpg   I have a similar heater that I bought here in the US, branded Holmes, made in China. It is rated at 1500 W, 120 V, 60 Hz. As a first cut, their product support page   http://www.holmesproducts.com/service-and-support/product-support/product-faqs/heaters/general-information/heaters-general-faq.html   says the "overheat shutoff temperature" varies from 149 to 265 F, or about 65 to 130 C. Note that this covers both ceramic and non-ceramic heaters.   Taking mine apart, the ceramic core is about 3.25 x 3.5 x 0.5 inches, or about 83 x 89 x 13 mm. If yours is very different than this, then it may need a different temperature rating!   The safety switch is an "open frame" design, like the one seen in the picture you linked -   > http://www.zuglet.com/ev/saturn/images/ceramicElement.jpg   - and not an enclosed one like the KSD301 Ebay link you gave. When installed, the bimetal with contacts is about 0.125" or 3 mm away from the top edge of the ceramic core.   It is marked AUONE, AUT95P, and has VDE and USA-Canada UL component marking ("backwards RU").   Google leads me to http://www.auone.com/showproduct13.asp?ProID=1849 . The part I have looks like their "AUT-P" series (with the white plastic tab), which lets me *guess* that the "95" in the part number means 95 C (or 203 F). Again, this is _just a guess_.   Please proceed with caution. The house you don't burn down may be your own.   Matt Roberds

Mike Tomlinson <mike@jasper.org.uk>: Feb 27 03:08AM >says the "overheat shutoff temperature" varies from 149 to 265 F, or >about 65 to 130 C. Note that this covers both ceramic and non-ceramic >heaters.   A useful data point, thanks.   >Taking mine apart,   You didn't have to go to that much trouble, but thank you.   > the ceramic core is about 3.25 x 3.5 x 0.5 inches, >or about 83 x 89 x 13 mm. If yours is very different than this, then it >may need a different temperature rating!   3.5" x 3.25", so very similar. There's 4 ceramic cores with two heat levels selected by a switch (heat level 1 = 2 cores operating, heat level 2 = 4 cores operating)   Ceramic elements are PTC so self-regulating to an extent.   >Google leads me to http://www.auone.com/showproduct13.asp?ProID=1849 . >The part I have looks like their "AUT-P" series (with the white plastic >tab)   That sounds like a resettable one.   >, which lets me *guess* that the "95" in the part number means >95 C (or 203 F). Again, this is _just a guess_.   It's also right in the middle of the "65 to 130C" shutoff temperature you quote above.   Many thanks.   >Please proceed with caution. The house you don't burn down may be >your own.   Obviously, I need to choose a sensible temperature for the cutoff - too low, and it'll trip on and off all the time. There is also a thermal fuse as a belt-and-braces measure at the top of the ceramic frame. I haven't looked to see what temperature rating it is. Obviously, if that fails, it will fail open permanently.   The ceramic element is held in place in a hard plastic frame, so isn't going to be allowed to get very hot.   I'll try a 95C switch with a temporary neon indicator on the feed to the element to see if it's cycling excessively, and go from there.   It's a nice little heater, very quiet and efficient, so worth a bit of time.   Thanks again.   -- (\_/) (='.'=) Bunny says: Windows 10? Nein danke! (")_(")

amdx <nojunk@knology.net>: Feb 26 03:47PM -0600 On 2/26/2016 9:21 AM, John-Del wrote: >> Anyone know how to get around this?   >> Mikek   > Not sure about the adapter, but most cable channels these days are letter boxed which means borders on the top.   If your Sony is set for 4:3 aspect in the HDMI input, that would give you 4 sides of black.   Try putting the Sony in widescreen mode for HDMI (assuming it isn't already)   Is there a separate setting for wide screen when using HDMI vs RF? I thought RF and HDMI would be the same, ie a global setting. To clarify, in RF mode it is full screen, switching to HDMI causes letter box. I'll poke around this evening to see if I can find something. Mikek

amdx <nojunk@knology.net>: Feb 26 07:06PM -0600 On 2/26/2016 3:47 PM, amdx wrote: > letter box. > I'll poke around this evening to see if I can find something. > Mikek   I found it! There is a screen setting in the menu of the DTA. Set it and it's good.   Thanks, Mikek

Cursitor Doom <curd@notformail.com>: Feb 27 12:42AM On Thu, 25 Feb 2016 00:36:16 +0100, Dimitrij Klingbeil wrote:   [...]   Dimitrij, I think you may have missed this I posted elsewhere so I'm re- posting it here now for you personally:   "Final update for the time being as I have to leave soon now:   That short turned out to be intermittent. I hope it was just due to something shorting out on the bench that won't happen when the casing is back on because you all know what a bitch it can be to trace intermittent faults. Anyway, that fault has now disappeared, so I took some voltage measurements before the 20W resistor got to hot (from 19'C to 60'C takes about 1.50s now) and I have:   61.7 12.7 5.8 0 -5.8 -12.7 -62.4   This is with the psu board plugged into the scope and all power connections made except for the VHT stuff.   The correct figures according to the manual should be:   60 12.7 6 0 -6 -12.7 -60   So very close! Looks like the main transformer may be ok after all."   Making progress! :)

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