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Jon <jms019@gmail.com>: Mar 22 05:01AM -0700 Thanks for that.

"Gareth Magennis" <soundserviceleeds@outlook.com>: Mar 21 10:17PM Hi,   I'm trying to fault find this amp.   http://tinypic.com/r/n3kxp1/9   The IC's are IRS2092 https://www.infineon.com/dgdl/irs2092.pdf?fileId=5546d462533600a401535675f1be2790     It very, very, occasionally goes bad one side. (this is 2 amps configured as bridged) I have replaced the bad side IRS2092 into a socket, but the exact same problem remains.   This is a real pain because it will run all day without the fault occurring, so it is difficult to find out exactly what is going on.     I did eventually get to capture some scope data under the fault condition. This is the output of both amps connected to an 8 ohm speaker.   It goes "boing, boing, boing", at a rate of just under a second. http://tinypic.com/r/316x93t/9     Zooming in a bit, you see http://tinypic.com/r/2du07sw/9     A bit more you get http://tinypic.com/r/33p55km/9     Zooming right in you get http://tinypic.com/r/34g53ee/9         The above screenshots are from the storage memory of the scope, so you will get quantisation anomalies as you zoom in closer.   Here is a real time screenshot of both amp outputs behaving normally. http://tinypic.com/r/2z4gsj7/9       From the schematic, you will see that both amp's switching frequency is adjustable via a preset. (not seen this before) So both are pretty much free running, thus not synced together at all.   However, if you adjust each to be close to the required 333kHz, they do actually sync together, hence the nice synced screenshot. (presumably this is from switching spikes via the power supplies) They don't care in normal operating conditions if they are synced or not.         I have changed ALL of the filter caps on the amp outputs, including the ones on the HT rails, thinking it might be an output filter problem, not the amp. The identical fault still occurs.       I'm still very much a beginner on Class D, but this kind of thing is becoming increasingly common, and I need to get my head around it.         Cheers,     Gareth.

jurb6006@gmail.com: Mar 21 08:43PM -0700 I hate those things. (figure of speech)   Exactly what happens to the speaker output when it fails ?

tabbypurr@gmail.com: Mar 21 09:26PM -0700 On Wednesday, 21 March 2018 22:17:21 UTC, Gareth Magennis wrote:   > Cheers,   > Gareth.   Analogue amps do similar things when their PSU caps go bad. Might be an area to look at.     NT

"Gareth Magennis" <soundserviceleeds@outlook.com>: Mar 22 08:36AM wrote in message news:0d0ae1ec-e3dc-4ddf-b84e-0226fa2609a1@googlegroups.com...   I hate those things. (figure of speech)   Exactly what happens to the speaker output when it fails ?     *************************************     This: http://tinypic.com/view.php?pic=316x93t&s=9#.WrNoppcuDIU     Total sweep time across the screen here is 2.4 seconds. I can only describe it as sounding like "boing, boing boing", with a boing every 0.8 seconds.       It is not VERY loud at all, nothing that would damage the speaker as far as I can tell, but this screenshot is the unfiltered output of the amps, not the filtered waveform the speaker sees. There are a whole bunch of inductor/cap/resistors between the amps and speaker.       Gareth.

N_Cook <diverse@tcp.co.uk>: Mar 22 09:09AM On 21/03/2018 22:17, Gareth Magennis wrote:   Are both amps, audio speaking , in phase or deliberately out of phase live Yamaha Stagepas (reduces the sag on reservoir caps on peak demand)

"Gareth Magennis" <soundserviceleeds@outlook.com>: Mar 22 09:27AM "N_Cook" wrote in message news:p8vrrh$r8t$2@dont-email.me...   On 21/03/2018 22:17, Gareth Magennis wrote:   Are both amps, audio speaking , in phase or deliberately out of phase live Yamaha Stagepas (reduces the sag on reservoir caps on peak demand)         ******************************************       They both share the same PSU rails, not like Stagepass.   The PWM signal to one amp input is inverted, making this standard bridge mode.   PSU is an SMPS.       Gareth.

jurb6006@gmail.com: Mar 21 08:45PM -0700 Just meandering thought here, what is the actual line voltage ? You know these old things were made to work on 110, not 125.

Fox's Mercantile <jdangus@att.net>: Mar 21 11:29PM -0500 > Just meandering thought here, what is the actual line voltage? > You know these old things were made to work on 110, not 125.   And as usual you are wrong. Per the manual: <http://w140.com/tek_565.pdf> The line voltage can be selected from 110, 117, 124, 220, 234 or 248 vac. 50-60 cycles.       -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com

gregz <zekor@comcast.net>: Mar 22 07:26AM > <http://w140.com/tek_565.pdf> > The line voltage can be selected from 110, 117, 124, 220, 234 or > 248 vac. 50-60 cycles.   120 normal here, and 125 up in building. I'll check that. I just saw a 500 vdc on power supply diagram. Not sure where that came from.   Thanks Gregj

"Ron D." <ron.dozier@gmail.com>: Mar 21 09:25PM -0700 I've had bad contacts on relays before. Both audio equipment and a programmable power supply. To fix the power supply, I wrote a program to open/close the relay every 10s overnight and the problem went away.   I'd measure the DC at the speaker terminals before and during a fault first. I'd expect something initially and probably zero if your loosing contact.   Then do the same, but before the relay.

Ralph Mowery <rmowery28146@earthlink.net>: Mar 21 05:56PM -0400 In article <447b1c87-d1a1-49ca-b6f4-9867a4cd95ea@googlegroups.com>, jurb6006@gmail.com says...   > >'I can make it act exactly like an analog scope if I want,"   > Oh yeah ? let's see the dot moving across the screen at 1 second per division and demonstrate it principle to students with a battery. I want to see it. A continuous dot moving slowly across the screen. I would bet a case of beer that you can't. Even a raster scan scope can't do it as far as I have seen.   > Do you have a really special one ? If not, it will blip blip blip refreshing the display and will not give you the dot moving slowly across the screen. If I am wrong, please supply me the make and model and I will reconsider and possibly retract.   My digital scope is an inexpensive Hantek and it draws a line like a pencil going across the page. At very low sweep speeds like one second or even less it makes it eaasy to see a waveform where the 465B with just the blip going across makes it difficult to tell what the waveform is.   Still my gripe is the Lissajous paterns will not display very well on the digital scope.   As in most cases it is good to have a choice between analog and digital test equipment. Sometimes one seems to suit the situation better than another.

etpm@whidbey.com: Mar 21 04:42PM -0700 On Wed, 21 Mar 2018 17:56:47 -0400, Ralph Mowery   >As in most cases it is good to have a choice between analog and >digital test equipment. Sometimes one seems to suit the situation >better than another.   I don't really need a digital scope, and from what I have read about them 100 MHz is pretty low for a lot of work. But the Hantek ones do get good reviews and are fairly cheap. So I might get one just for fun. Eric

jurb6006@gmail.com: Mar 21 08:10PM -0700 >"One of my daily use digital scopes at work is an old Tek TDS460a, it'll scan across the screen as slow as 20 seconds/division."   In my albeit limited experience with sampling scopes I have never seen one do that. I also noticed like noise in the trace that was indiscernable which I thought would be on an analog scope.   I guess I'll have to test drive one. Speaking of driving :   >"You could still drive a Model T cross country, but would you? "   Yes I would and I would love every minute of it. But I admiot that it would not be a daily driver.   >"Analog scopes had their day. That day is over."   Not as long as they work. You know there are people who can't stand an LCD TV. I have read that some have a wider optical response to the spectrum, perhaps that is the reason. But they either stick with CRT TVs or buy a plasma, I guess because it is actually a phosphor screen.   But so far I have never met a digital scope I liked. Of course that may change in time.

jurb6006@gmail.com: Mar 21 08:29PM -0700 >" My digital scope is an inexpensive Hantek and it draws a line like a pencil going across the page. At very low sweep speeds like one second or even less it makes it eaasy to see a waveform where the 465B with just the blip going across makes it difficult to tell what the waveform is"   As I told Terry S., I have never seen a digital scope do that. And emulating a variable persistence CRT, well that is cool as well. i still like the old scopes. If I were a billionaire I would but an older car. A 1960s or 70s high powered gas guzzling monster that should be licensed as a deadly weapon. My first car was a 1970 Olds Toronado, I still had passing gear at 105 MPH. I know newer cars with much smaller engines can go just as fast, but this thing did it effortlessly. P{ush a 4 cylinder to those limits and you are beating on it. Variable valve timing and direct cylinder injection is nice but it has thousands more moving parts. To move is to wear.   Maybe I am an old fuddy duddy, but I like it, and the old music. I welcome a lawsuit from RIAA because the gigs of music I downloaded used to be in public domain. In fact even movies. Everything I like is old. New and improved is an anethma to me.

Clifford Heath <no.spam@please.net>: Mar 22 11:23AM +1100 >>> 5 snap closed ferrite cores around the power cable going into the laptop >>> but they haven't helped. Thanks.   >> Get rid of the inverter. They are all horrendous noise sources.   Not all of them. Unfortunately price is no indication however. We've used quite a few different inverters for our in-car fox-hunting gear, and some cheapies are quiet, some $$ are noisy. You just have to suck it and see in most cases.   No, I don't know brands and models - been away from this for a few years.   > As is the car itself or anything else operating near it.   Cars can produce lots of interference, or next to none. At least with a car you can usually chase down the cause and perhaps cure it.   Clifford Heath.

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