I am deaf in one ear and cannot locate the direction from which a sound originates so I was relying on the balance knob and not the speakers, to tell me that the left channel was dropping out, even when I switched the preamp right and left outputs into the power amp inputs. That was an entirely erroneous episode of troubleshooting. The balance knob continued to to tell me that the left channel was dropping out, but in reality the output at the speaker jacks was switching from the left to the right channel. I only discovered this when measuring the AC voltage at various points in the power amp wiring. I was puzzled at the readings I was getting and went to the speaker jacks where the speaker wires were connected.
Long story short, the dead channel at the speaker jacks switched from left to right when I switched the preamp outputs going to the power amp inputs.
I have to put this aside for a minute and re-read all the relies I have gotten dealing with possible cause on the preamp side of the unit.
My apologies to all who followed me down the wrong path with this unit.
Why am I reminded of André De Toth, the director of "House of Wax", who was blind in one eye?
ARRRGGGHHH!
Lemme tell you a story...
Way back in 1980, when I was living in PA, an acquaintance asked me to help a friend diagnose a problem with his Dayton-Wright preamp. I don't remember what the problem was, but there _was_ an obvious likely cause.
"Did you check thus-and-such?" "Yes." "You're absolutely certain?" "Yes." "You're really, really sure?" "Yes." "Okay, bring it over and we'll have a look."
I hooked the preamp to my Lux Laboratory Reference Series components, and when I moved the input selector switch, both output stages of the power amp were blown out. "Pissed" is hardly the adjective.
Naturally, I sent the guy packing -- and the power amp to Lux for repair. (That's called "zeugma" -- one verb yoked to two subjects.) I later learned that he had not properly checked out the unit, and that my original suspicion as to the nature of the problem was correct.
There are several points to be made. One is that it's not a good idea to help people who you don't know, especially when you're not being paid for it. Another is that you should thoroughly check someone else's equipment before you put it in your system. * (DC offsets and output oscillations are good things to look for.)
But the most-important point is that you can't trust other people to correctly describe what's wrong with their equipment. Heck, you can't even trust yourself! How many times have you gotten thoroughly confused as you work your way through the diagnosis?
Nevertheless, I hope Readily Visible's SX-838 bursts into flames while he's asleep, burning his house to the ground and destroying all his possessions. And his little dog, too.
In this case, I wouldn't have caught the problem. It turned out that the Dayton-Wright preamp used switches that were very good at generating RF when opened or closed. The RF caused the triple-diffused output devices in the Lux 5M50 to melt from tertiary breakdown, a known problem with this power amp. (Ironically, Mike Wright was aware of the RF problem with the preamp, and had added holes to the PC board for suppression caps. Unfortunately, the holes were not populated.) This was not the first nor the last time this happened; the next time was my own stupid fault.
It's not enough that someone (me) pokes public fun at his foolishness. You have to rub it in by calling him stupid, as well. For a person who (apparently) doesn't have a lot of experience servicing equipment, you not only lack a sense of humor, but you're quick to snipe at someone who probably knows a lot more than you do, you rude louse.
God knows, it took long enough. The next time you want help, don't expect me to be offering it.
Unless you're well past 40 (or so) I was servicing electronic equipment before you were born. And I worked as a paid technician for a short time. The store owner (Jack Rubinson of Chestnut Hill Audio in Philadelphia) complimented me for never having callbacks. I made sure stuff was properly fixed before it went out.
By the way, the next time the output transistors in the Lux blew, I replaced and rebiased them myself. It was no big deal. But the amp is still working, over 25 years later.
Considering all the hoops that every one of the good folk on here have gone through in order to try to help you, I would suggest that you stop pursuing this line of posting right away, otherwise, I can see it descending into a name-calling session that you really wouldn't want to be on the end of. William has been mild in his chastisement of you, compared to how some may be, if you wake them ...
So, after all that, you say that you have now fixed it. Perhaps out of courtesy to the group, and all those professional people and gifted hobbyists who took the time and trouble to try to point you in the right direction, you would be good enough to share with us what the problem was ?
The real problem is that both the DW preamp and the Lux power amp were just more examples of poorly-designed high end junk.
The world is full of fine-sounding preamps that don't create RF-rich transients when you operate their controls. Many of them create no audible transients at all! The world is similarly full of fine-sounding power amps that don't melt down every time you drive them with a few transients, or even a lot of transients.
It would be interesting to know what fraction of the total production of Dayton-Wright audio products are still in service. It's my recollection that DW briefly rose to fame on the strength of an interesting idea with a lot of potential - sealing electrostatic speaker elements in thin plastic envelopes full of an insulating gas. Unfortunately, they were also the reactive loads from #&!! and could and did fail frequently in actual use.
As far as the fail-o-matic Lux power amp went, Lux had been around for a long time even way back then. They should have known better. Apparently their transition from tubes to solid state was not smooth. Lots of people built very durable power amps with triple-diffused output devices. No doubt Lux figured it out, or simply went out of business due to their technical incompetence.
For their time, none of the Laboratory Reference Series products -- except the 5T50 tuner -- was particularly expensive. * They weren't cheap, but they weren't Mark Levinson, either.
Junk is in the eye of the beholder. All my LRS stuff continues to work, though it's more than 30 years old.
According to the guy who fouded Kinergetics, the 5T50 was designed to "sound like" the Marantz 10B. I don't know if it did or didn't, but several reviewers felt that the 5T50 was the first digital tuner that "sounded good", supposedly because Lux did a good job keeping the digital "junk" out of the audio circuits. This ought to be a trivial engineering exercise, so if the 5T50's sound was surperior, it was likely for another reason.
I don't know why Willaim Watson Michael Dayton-Wright chose those particular switches. If you want to damn him, damn him for not installing the caps.
As for the power amp... At the time it was designed, there was a lot of arguing about slewing-induced distortion, TIM, and the like. (There were tube power amps that suffered from these problems. Dig through your early-80s JAES issues for an article about one.) The assumption was that, the wider the open-loop bandwidth, the less likely TIM would be a problem. So Lux used triple-diffused RF power transistors -- despite the common knowledge that they could be blown by RF transients. That was the cause in three cases where the output transistors blew -- not audio transisents.
use.
The Dayton-Wright electrostatic speakers could, with a suitable amplifier (such as Crown M-300) play at near-earsplitting levels in a large, dead room, cleanly. I do not recollect the panels having a reputation for failure, though I could be wrong. The use of SF6 as the dielectric gas reduced arcing, which is the principal (thought not only) cause of panel failure.
These speakers were among the hardest-to-drive loads, ever. There was a bass impedance peak of around 100 ohms, while the impedance fell to less than 2 ohms in the upper midrange. If the amp couldn't pump the required current (and some couldn't, even at moderate levels), you'd hear "current clipping".
One might equally ask "What fraction of the total production of Company X's products are still in service"? The switches and electrolytic caps are the quickest components to deteriorate. I have (and have had) stuff over 40 years old, and am amazed that it continues to work.
Arny, you have a good vocabulary, so why not use it well? "Fail-o-matic" suggests self-destruction, which this amplifer was /not/ prone to. (I could name another brand of amplifer which, in my experience, repeatedly self-destructed for no obvious reason.) It was damaged when subjected to a form of electrical abuse that Lux naively assumed would never occur. Lux should have added low-pass RF filtering outside the feedback loop.
Who? My understanding was that designers generally refused to use these devices, precisely because of the known problems.
Lux is still in business (I think), though a shadow of its former self.
And before we go... I have to acknowledge Arny's real motivation in posting this. He just loves kicking people who own not-cheap equipment with less-than-perfect reliability. "If only you'd bought Grommes, you wouldn't have had these problems."
Given all the time that people have spent, at no charge to yourself, to help you fix a problem which, honestly, you don't seem competent to diagnose and repair yourself, I find it in incredibly poor taste to make the comments you have. This group has a very talented and extremely experienced core group of techs like William Sommerwick, Arfa Daily, Mark Zacharias and (the resident cynic) Arny Krueger who have been nothing less than courteous and polite in their unfunded efforts to help you. Then, after you wasted all of their time by posting erroneous information, you have the GALL to insult them? I'd suggest you review the facts and lose the attitude, ye cad.
Yeah, that's incredibly rude. If you need advice from other people, have a bit of humility or f*ck off. If you were *that* superior, you wouldn't need to ask for help.
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Jeez, for someone who can't even spot a dry joint or a grotty relay contact without help, you sure have one hell of an attitude! I notice that you didn't act like this *before* your amp was working again.
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I have an excellent -- indeed, I'd say exceptional -- sense of how to go about diagnosing problems. But I don't have the in-depth, day-to-day experience Arfa, et al, have.
I used to service most of my own equipment, but consumer electronics have become so complex and so fundamentally un-repairable that I rarely repair anything. The last item I fixed was one of my electronic crossovers, replacing an output drivers. (Believe it or not, John Curl helped me diagnose the problem, by pointing out something I'd overlooked.)
One of the reasons I'm here is that I like to see what's going on in electronic servicing, and get a better view of how the "new stuff" works. You never know when it might come in handy.
I'm about the same as far as experience goes. Background in electrical engineering (long long time ago), used to repair just anything, but have never had the urge to move into SMD work, my eyes probably aren't good enough anyways. Most of the repairs of newer TV's, multi-channel amps, etc. seem to be board replacements, which holds no interest for me... I like the troubleshooting process itself and get great pleasure from being able to take a doorstop that cost somebody $1,000 long ago and turn it back into a great amplifier or TV or washing machine or for the cost of a few caps and a $1 regulator or $5 IC. My collection of TV's, stereo equipment, etc. was in large part received for free in non-working condition, and I doubt I've got $100 in any single piece. My wife calls me a packrat but doesn't complain about my rates...
This group is a gold mine for experience, and it annoys me to no end when people dare to complain about ABSOLUTELY FREE advice and assistance. Advice gleaned here has helped me to repair items of which I initially had little or no understanding.
We all have skills that nobody else here has. Between us, we cover a pretty amazing amount of territory.
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I'm a bit of a noob here, but I racked up about 5 years as a service tech for computers, faxes, laser printers & inkjet printers. Then another few years as the national Technical Specialist (ie; the go-to guy for the entire country) for laser faxes & photocopiers, then a few years doing actual electronics design work, followed by about 5 years running a service department for laptops, lasers, inkjets & PCs. Since then (10 years?), I've worked in networking, security & general IT consulting. I don't know that much about troubleshooting consumer goods (other than what I've done for myself or friends), but I do know my stuff in my areas.
Ditto. The gang here helped me repair my Tek oscilloscope, & were about as nice & helpful as you could possibly imagine. I can't think of anywhere else I could go, & get that quality of expertise. And it was FREE! What kind of moron would argue with that?
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I don't think that was implied. You seem to be well informed and have an air of modesty about you. That often is better than pure on the bench experience where the Average Joe stumbling across tech groups is concerned.
I myself am considerably out of the loop on current day consumer electronics by choice. I prefer pro audio equipment more specifically things with glowing tubes in the power section or older discreet circuits with mosfets and the likes.
However, my troubleshooting techniques still apply to a broad range of equipments and I'm not afraid to tackle anything if the need arises.
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