Integrated amp problem...can anyone help?

[Beagle]

Any electronic experts here?

My Luxman L5 intergrated amp has gone on the fritz. I leave it powered on and last night I went into the room and noticed it was in "warm-up" mode, the red power indicator light was flashing.

With the Luxman, when you press the power on button, the red light flashes for about 10 seconds (apparently a surge protection feature) then clicks and it's powered on, and the light stays constant red. But now it's flashing on and off continuously and no sound. I had the fuses tested and they checked out OK (apparently, but not sure if I can trust Radio Shack rookies). I unplugged, plugged back in, and it won't "click in" to power mode. It just stays flashing.

Anybody have any idea what the problem might be? The amp is 22 years old but a good one, very clean sounding, and I'd like to keep it if at all possible. The fact that it apparently happened while the unit was already powered on kind of bothers me

Any advice would be greatly appreciated!

[Dave]

Beagle,

Pull the top cover off and take a look inside and make sure the capacitors aren't leaking, also look for fried resistors. If the PC board looks good take it into a more experienced electronics shop and have them test the power transformer.

When Sckott shows up I'm sure he can be of better assistance than I.

[Sckott]

Thanks.

Well, it's down now. Don't worry about the fact that it went on the "flitz" while it was on. I've seen huge caps go up in smoke, I've seen chips built in to a PC motherboard fly out burned like chinese stars. Damage is damage.

Dave is on the right track. I don't think the power supply is performing well. There has to be enough voltage cap for it to power the amp. However, it could be something like a proprietary FET that's gone. Those can sometimes be difficult to work around.

With most amps, the first section to cripple itself is the power supply. In this case, and I'm only guessing, the power supply can't hold enough voltage to start.

Did you smell anything blow? Sometimes you can't. Some caps bow out with almost no drama. You just have to see if any electrolytics are puffed up and blowing a seam. The other things you would check is a diode that may have shorted to "0". A simple volt meter would be useful. In most cases that I've seen, a diode fails, and the power charge goes back and busts a cap. There's no way energy gets dumped, so the cap takes a hard hit.

I've repaired about 8-10 power amplifiers, and the combo of faults go down like a crime. It's kinda neat how it could be just a cap here, but if a diode goes and doesn't rectify, the rest of the section gets handed voltage-whoop-***.

If you have the skills, bravery, a volt meter and a good soldering pencil, go search through the city of caps.

If you don't, PLEASE get someone experienced on the case. I wouldn't worry much about your amp. If you can get someone who can easilly do board level repairs, you're in good hands. With most older amps, many of the sections were built simple part-wize, but were fairly elaborate, in which section after section is chaotic with resistors at every attenuator, stages upon stages. The Sherwood I'm trying to ressurect is much like that. It's bananas, but a good challange.

Get a good tech behind it, and express your desire to keep it in use. Don't give up the ghost, and think that you'll have to put it to sleep.

If you have any major hassles with getting it fixed, let me know.....

[sgraham]

The first thing to check is to make sure none of the speaker cables are shorted. If a little strand of wire finds its way across the terminals it'll short and cause the protection circuitry to come on. If that's not it you could have a fried output transistor.

Or, of course, a myriad of other possible things.

[Gary]

Originally posted by sgraham
The first thing to check is to make sure none of the speaker cables are shorted. If a little strand of wire finds its way across the terminals it'll short and cause the protection circuitry to come on.

Great idea! Or check inside for a short!

My HK amp has a protection circuit like that. Thankfully, all is well... so far.

And I even know of places here in town that will do repairs!

[Beagle]

Thanks very much (special thanks to Sckott) for taking the time to provide your analysis and advice.

I actually don't have my speakers hooked up, I have been using headphones with this amp.

I did not smell anything unusual, but something might have occured during the day while I was at work, I leave it powered on all the time.

I have some good contacts for repair so I'll get it looked into, hopefully it won't cost an arm and a leg. But I will look under the cover to see if there are any visible problems.

[Sckott]

Let us know..... :p

[Ed Bishop]

:rolleyes: I have an old late '70s Sansui amp that occasionally does what Beagle described. Working just fine, then all of a sudden the protection circuitry kicks in, and you can't hear a thing...seems to happen more in winter than summer; it's in the basement where it's slightly cooler, so maybe that's the problem. Yet although it's a temperamental little beast, can't part with it: great high and low range sensitivity. Whenever I really want to analyze a digital remaster, I use that machine(with Stax phones)because the top is so subtle if an engineer dampens hiss 'on the fly' on certain passages rather than others, I can hear it(as on the first CD pressing of Miles' IN A SILENT WAY, to name just an obvious example). Tape editing? This thing will pick it up even if it isn't readily apparent through the main system. I don't use an equalizer with it, though I've got one and the prospect has always been tempting...but once you start in with special Eq levels, it can get out of hand mighty fast. Better to just listen to the recording flat and judge it fairly...
An audio shop owner once gave me a few pieces of advice. Before you bring in any hunk of equipment, do first: unplug the deck, then replug; see what happens. Second: your own power supply. We had problems at the house with some outlets causing a certain breaker to trip; turns out, after 30 years or so, a few breakers were shot. Went to a True Value hardware store, bought a few new ones, put 'em in, and everything works fine. After that, bring it in, needless to say and most of all if you ever DO smell something funny. Most amps and receivers will give off a 'pleasant' kind of smell if you really want to stick your kisser close enough, which I don't recommend. But if something really does stink, don't play games. Just bring it in and pray to whatever gods you worship there's nothing seriously wrong. Like music, I tend to foolishly fall in love with components; I've never gotten over my quad-8 deck going into the tank. I still wish I had it--say, just to listen to AUTOBAHN in 4-ch once in a blue moon--and probably wouldn't have been that expensive to fix. Since that stupid blunder, I've thrown nothing out.
Just one more thing: if you do have to bring the piece in, try to use somebody you already know. I have a few friends I deal with when I have to; they're also great for used stuff if I need anything. We've got one guy in town who's an audio ace, but his personality is shiite and I don't deal with him; smarmy, arrogant SOB. I travel 50 miles to a buddy instead.


Good luck Beagle,

ED:cool:

[Beagle]

Originally posted by Sckott
Let us know..... :p

OK, I have my amp back from the shop. They replaced 3 transistors, 2 resistors, 1 capacitor and did a thorough overhaul. Apparently the worn or faulty parts were causing the amp to stay in 'protection' mode. Anyway, it now sounds wonderful, clean as a whistle, no more static and noise in the volume control and the whole thing sounds cleaner, smoother. I'm happy. $100 poorer, but happy :D

[Dave]

Originally posted by Beagle
$100 poorer, but happy:D
Wow! Glad it worked out OK Dave. Could have been alot worse, you actually got off quite easy IMHO.;)

[Sckott]

$100 for all that was possibly plaguing the power supply section. Atta boy, Dave!!

That's not bad concidering he took care of possibly everything that can die within your lifetime. It should last a very long time now.