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Cursitor Doom <curd@notformail.com>: Feb 23 06:43PM On Mon, 22 Feb 2016 08:49:11 -0500, legg wrote:   > If it's slow, it looks like a short when the power transistor is trying > to turn on, stressing the current snubber around L1804.   I don't think this diode is the culprit, TBH. Just out of curiosity I hooked it up and tested it this afternoon. The faster diodes turned up so I thought it might be instructive to compare them. The main flaw in my test is that I'm unable to replicate actual working conditions. I just hooked up each diode in series with a 1k resistor and fed the arrangement from my 600ohm sig gen using 10VAC p-p. Slow recovery was certainly visible on the scope with the BY134, but it wasn't *that* bad. In fact it was still able to function as a viable rectifier right up to nearly 600kHz. There were no signs of slow recovery with the UF4007 of course, but the difference at 20kHz, whilst still noticeable, is unlikely to be causing the issues I've experienced. But as I say, it was in no way a scientific test and only when the new diode is in circuit will we know for sure. I won't be holding my breath!

Dimitrij Klingbeil <nospam@no-address.com>: Feb 23 11:33PM +0100 On 21.02.2016 14:46, Cursitor Doom wrote: > termination unit so it's readings will be meaningless and I can't > use the true RMS current range on my DVM because it's probably going > to be out of its bandwidth at this frequency range. :(   Ok, there are other simpler ways to test windings under high voltage :)   See below for a simple test circuit that would be easily doable with a few common parts and works like an IWT (impulse winding tester):   <http://imgur.com/2qfjhaX>   It needs a power supply (can be just a mains isolation transformer with rectifier and capacitor) and it's intended to show the resonance waveform on an oscilloscope at realistic rated voltage conditions.   The MOSFET (any 400 or 500 V type with less than 1 Ohm Rdson) is driven with a square wave from a signal generator (frequency should be slow enough to allow the cap to recharge, some 50 to 100 Hz) and discharges a capacitor from 320 V (rectified isolated mains) into the inductor under test. Under discharge conditions the capacitor and the inductor form a resonant circuit and slowly "ring down".   The resistor heats up with prolonged operation, obviously, since it has full supply voltage across it, so that's why it's rated 10W.   The waveform is measured (due to the high voltages involved) with a 400 V rated 10:1 oscilloscope probe. It should give a reasonably reliable indication whether an inductor (or a transformer) is good for use at full mains voltage or not.   The circuit works similarly to a commercially available IWT and it's intended to be connected to the primary of a transformer. The waveform should look like a typical IWT waveform (search for "impulse winding tester" in Google Images to see what it looks like).   Here's a good looking waveform example:   <http://meguro.com.my/wp-content/uploads/2013/05/Impulse-applied-chart.jpg>   A shorted (or otherwise overloaded) coil will decay very fast or even hardly resonate at all. A good one will resonate for many cycles.   A failing one with significant corona discharge may look like this:   <http://www.ucetech.com.cn/en/App/Tpl/Home/Uploads//day_150908 /201509081505159156.jpg>   This test should be easy to do, and should be able to settle the question if the transformer is "shot" with reasonable confidence.   As always, when working with high voltages, pay attention to safety!   Regards Dimitrij

Dimitrij Klingbeil <nospam@no-address.com>: Feb 24 12:04AM +0100 On 23.02.2016 19:43, Cursitor Doom wrote: > experienced. But as I say, it was in no way a scientific test and > only when the new diode is in circuit will we know for sure. I won't > be holding my breath!   Well, I don't think that it's the main culprit either. But it may impair the working of the energy recovery circuit far enough to make it inefficient, forcing it to dump too much power into the resistor. If everything else was well, that might still have worked to some extent.   But you're trying to troubleshoot it, and something is obviously wrong that causes the resonant circuit to appear as too low impedance. Either the transformer is broken or the output circuits (rectifiers) or the whole thing is operated on wrong frequency too far out of resonance.   If the energy recovery circuit was working well, it should be able to protect the resonant circuit, even at some overload, by diverting the energy back into the main capacitor. That would allow you more time to "probe around", checking what is the cause of the overload.   Slow diodes usually become worse with rising currents, so one that is able to drive an 1k resistor from a signal generator may just as well behave like an RF short circuit if one tries to push significant amps through it. So it's really difficult to compare.   Anyway, while I don't thing that it's enough, I was hoping that making that part work efficiently again would at least lower the load on the resistor to some extent, and give you more time for such more complex things like resonance frequency measurements or even adjustments.   Also, as for testing the transformer (out-of-circuit, with a poor man's IWT equivalent), see my other post.   Regards Dimitrij

Cursitor Doom <curd@notformail.com>: Feb 23 11:23PM On Wed, 24 Feb 2016 00:04:13 +0100, Dimitrij Klingbeil wrote:     > Also, as for testing the transformer (out-of-circuit, with a poor man's > IWT equivalent), see my other post.   > Regards Dimitrij   Many thanks as ever for your thoughts, Dimitrij. One question on your other post before I forget: your schematic shows pulsing the transformer input at 100Hz, so we're just testing the primary winding in this instance, right? We're not concerned in this test about what's coming out of the secondaries? I assume so because 100Hz is so far off its intended frequency range but would be grateful if you'd confirm if I have this right.   I fully agree with your observations on my diode test's shortcomings.   The only other thing I'm waiting for is some replacement caps for the original tropical fish types that don't look very healthy. They test okay at low voltage but may be misbehaving badly at closer to their working conditions. They're in really poor shape visually and I could certainly believe THEY might be responsible for the issues I've had. They should be here tomorrow or Thursday so by the end of this week, I should have some firm results one way or the other.

John-Del <ohger1s@aol.com>: Feb 23 03:40PM -0800 On Tuesday, February 23, 2016 at 6:26:58 PM UTC-5, Cursitor Doom wrote: > believe THEY might be responsible for the issues I've had. They should be > here tomorrow or Thursday so by the end of this week, I should have some > firm results one way or the other.     I haven't read all the posts, but way back when I suggested pulling every cap and checking for value and ESR *out* of circuit. Have you done that?

Cursitor Doom <curd@notformail.com>: Feb 24 01:17AM On Tue, 23 Feb 2016 15:40:12 -0800, John-Del wrote:   > I haven't read all the posts, but way back when I suggested pulling > every cap and checking for value and ESR *out* of circuit. Have you > done that?   No. Normally that would be one of the first things I'd do, but the traces on this board are old and brittle, so I'm avoiding upsetting them until I've exhausted other possibilities (drawing ever closer now). The few I am replacing this week are clearly in sub-prime condition from visual inspection alone. I'm suspicious of these (metalized polyester types) more than the "usual suspects" electrolytics in this particular case.

legg <legg@nospam.magma.ca>: Feb 23 10:46PM -0500 On Tue, 23 Feb 2016 18:43:40 -0000 (UTC), Cursitor Doom >causing the issues I've experienced. >But as I say, it was in no way a scientific test and only when the new >diode is in circuit will we know for sure. I won't be holding my breath!   If you've got UF4007s, then what are you waiting for? Polyester film caps in low voltage circuitry are the last things to suspect. Their perfomance is most easily assessed in the working unit.   After making whatever node tests are made convenient by the transformer's absence, stop screwing around and reassemble the unit.   No benefit is obtained by running the unit unloaded unless the loaded outputs produce non-typical loading effects, as measured on the transformer output windings and rectified outputs.   Unstable waveforms will produce the same voltage ratios as a steady signal. The present switching circuitry is an excellent signal generator for the application, having survived all insults so far.   RL

Cursitor Doom <curd@notformail.com>: Feb 24 10:19AM On Tue, 23 Feb 2016 22:46:21 -0500, legg wrote:   > If you've got UF4007s, then what are you waiting for? Polyester film > caps in low voltage circuitry are the last things to suspect.   Even if there are bits flaking off them?? That's the case here!   Obviously a professional technician just wants to get each unit fixed as soon as possible so as to get on to the next one and maximise his income. But I'm just a hobbyist and my motivations are not at all the same. Of course I'd like to get this up and running, but if I don't *learn* something from the experience, then it'll be next to worthless AFAIC. So you might see it as screwing around to run these side-by-side diode tests from your perspective, but I really don't. This unit is beyond economic repair, but I'm still working on it - for a little while longer anyway - whereas a professional service person could not afford the time on what he would see as a basket-case.

John-Del <ohger1s@aol.com>: Feb 24 04:26AM -0800 On Wednesday, February 24, 2016 at 5:22:37 AM UTC-5, Cursitor Doom wrote:     > Obviously a professional technician just wants to get each unit fixed as > soon as possible so as to get on to the next one and maximise his income. > But I'm just a hobbyist and my motivations are not at all the same.   Well, that's how I look at it. But I do remember back when I was a teenager working on what was then new technology (transistorized TVs) and the boss trying to get me to check the "Goldenrods" (RCAs service bulletins back then). I didn't want to because I wanted to track the problem down myself.   Even today on a slow day, I'll spend a lot more time on something that isn't economically worth the effort just to solve the puzzle. Even us old grizzled veterans aren't immune to such things.

Cursitor Doom <curd@notformail.com>: Feb 24 04:25PM On Wed, 24 Feb 2016 04:26:28 -0800, John-Del wrote:   > Even today on a slow day, I'll spend a lot more time on something that > isn't economically worth the effort just to solve the puzzle. Even us > old grizzled veterans aren't immune to such things.   Well I'm pretty old and grizzled myself! Just getting stuck back into troubleshooting again after a 30yr. lay-off. So much has changed! Anyway, the plan was to replace one suspect part after another one at a time and test in between each replacement so as to identify the specific part which is at fault (the new caps arrived today, btw). However, I only got as far as replacing that diode (the by134) with Dimitrij's suggested 4007 and *something* has *definitely* changed. The 20ohm power resistor is warming up *much* more slowly and the hissing noise has gone. The limiting factor now is not the 20ohm resistor, but the improvised dummy load (a 30ohm 40W w/w resistor) which gets too hot long before the 20ohm circuit-board part. In fact even with the dummy load disconnected, the 20ohm resistor doesn't get hot in a hurry like it did before. So like I say, *something* has changed and that something can only be the diode swap. Can't believe it would make that much difference, surely? More testing as soon as I find a better DL...

mroberds@att.net: Feb 24 06:15AM > the page proclaims that they offer "Passionate Customer Service". It > might be worth buying their battery just to try out their customer > service.   Post pics!   Matt Roberds

Jeff Liebermann <jeffl@cruzio.com>: Feb 24 08:21AM -0800 >> service.   >Post pics! >Matt Roberds   Right.   Long ago, in a legendary electronics paradise called Silicon Valley, I was a young, naive and inexperienced circuit designer. When I would contact a vendor begging for data sheets, prices, and samples, they would usually be accompanied by a visitation by a salesperson, usually with a highly creative title and elaborate business card. My job was to pry the information and samples from their possessive clutches. They seemed to believe that only the truly worthy may view or posses these jewels. After a few mistakes, I learned the necessary protocols and was able to get the job done without much difficulty.   One day, I received a visit from a local PCB house wanting my business. Instead of an aging and burnt out male sales engineer in a seriously expensive suit (with white shoes), I was accosted by a gorgeous former fashion model. Not only did she match my idea of what constitutes beauty, but she also knew the PCB business quite well, and was familiar with most of the problems we had with environmental requirements, testing, and RF specific problems. I was thoroughly infatuated but tried not to show it. I also had no idea what to do, made a fair simulation of a fumbling idiot, and accidentally handed her copies of some confidential papers (which I later recovered).   Before handing the business to the gorgeous former fashion model's PCB house, the high command demanded that I get competitive bids. I called two other local PCB houses, and was blessed with two additional gorgeous former fashion models selling PCB boards. Apparently the technique was so successful, that other PCB houses had adopted the same strategy.   As one might predict, I again simulated a totally useless fumbling idiot. The problem was obvious and responsibility for juggling PCB vendors was handed to someone older, married, and allegedly immune to the salespersons charm. I was also marked as some kind of sex maniac, not to be allowed anywhere near beautiful salespeople.   I presume that the Chinese battery vendors have discovered the method and are using it to their advantage.       -- 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

N_Cook <diverse@tcp.co.uk>: Feb 24 03:42PM All working again as far as all of the pots are concerned and 3 of the pull controls change the sound. No magic smoke or anything overheating. The pull options of Treble- Pull shift Master- Pull deep Lead Drive - Pull Lead Lead Master - Pull Bright no change of sound. It'll be awkward if the "repairer" blew some of the LDRs, but at least they can be checked for function with a low ps only.

"Snuffy \"Hub Cap\" McKinney" <Snuffy-Hub-Cap@Livebait-McKinney.com>: Feb 23 09:46AM -0800 Great little TV until this morning when it indicates "No Video." I went thru all the setup menus but nothing for troubleshooting or setting for video.   I moved it to another connector with a good signal used for another TV and still shows no video. Put good TV on Toshiba connector and shows good signal coming in.   Any ideas where to start troubleshooting before heading off for another one?   Toshiba Model 22C100U Nov 2010

"Snuffy \"Hub Cap\" McKinney" <Snuffy-Hub-Cap@Livebait-McKinney.com>: Feb 23 03:37PM -0800 "Snuffy "Hub Cap" McKinney" <Snuffy-Hub-Cap@Livebait-McKinney.com> wrote in message news:iaqdnWuWK4aKBlHLnZ2dnUU7-bWdnZ2d@earthlink.com... Great little TV until this morning when it indicates "No Video." I went thru all the setup menus but nothing for troubleshooting or setting for video.   I moved it to another connector with a good signal used for another TV and still shows no video. Put good TV on Toshiba connector and shows good signal coming in.   Any ideas where to start troubleshooting before heading off for another one?   Toshiba Model 22C100U Nov 2010   ---   False alarm. I checked the input settings. It was set properly, so I went to the set up menu, reset the set and all is fine again.

avagadro7@gmail.com: Feb 23 12:41PM -0800 first plug after posting has print above the ground pin.   when I find 10 similar surely the 11th would not n start a fire in the basement.

Cydrome Leader <presence@MUNGEpanix.com>: Feb 23 07:13PM > get a step peak on the out sides of the sweep before it changed > direction.   > Neat stuff for back then, real engineers not uC coders!   Did all this stuff make an electron beam?

Adrian Caspersz <email@here.invalid>: Feb 23 06:53PM > I want To hook a car amp and use car woofer can I run it thermal fuse   To detonate?   -- Adrian C

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