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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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