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Protect mode problem -- Sony STR-DE597

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I have looked through the threads about other people's protect mode problems, and I found many helpful suggestions, but I still can't fix my problem.

My Sony STR-DE597 receiver is less than 6 months old. It worked great for about 3 months, then it continually goes into protect mode after about 20 minutes of use. This will happen no matter what input I’m using, either an optical or an analog (RCA cable) connection, and will even happen when I use the FM tuner. Volume level or tone seems to make no difference, and I mainly use the receiver for soft background music. I only use two speakers and shut off all of other possible speaker configurations using the receiver’s menu, and this problem has occurred when I’ve hooked up the speakers as the A speakers AND the B speakers. I have even got it to go into protect mode using the FM tuner and having no speakers connected to it at all. I cannot immediately turn the receiver back on after it shuts off automatically—if I do, it will flash “PROTECT” again and shut off—but after five to ten minutes I can turn it on again, only to have it go into protect mode after another 20 minutes or so.

I bought the receiver at Best Buy with an extended warranty. I brought the receiver into Best Buy twice, and they were unable to replicate the problem either time. Unfortunately, I don’t know exactly how they set it up to test it. When I set up the receiver again after the second time I brought it to Best Buy, it worked well for about a week before it starting regularly going into protect mode again. I noticed that the receiver was getting very hot on top of the cabinet towards the right side. So I added gold banana plugs to all of my speaker cables. After experimenting with the speaker setup, I found the following: hooking up the left speaker (of the A set) makes the receiver get hot. I also noticed that the left speaker will make a “popping” noise when I first turn the receiver on and the input is already on or if I immediately switch it to the tuner. The hotness and popping occurred with both of my speakers, using both speaker cables, as long as they were plugged into the left speaker jack. I thought I could conclude that it wasn’t my speakers or my connection, so I left the receiver running with only the right speaker plugged in (the A set)—the receiver didn’t get hot, but it still went into protect mode and shut off after about 10 minutes.

So, I brought the receiver into an authorized Sony service center, and they, too, were unable to replicate the problem. They evidently had the tuner running for days. I’m really at a loss here. It doesn’t seem to be my setup (speakers/connections or inputs), so the only thing that I can think of is maybe the problem has something to do with electrical current, but I’ve tried the receiver in different outlets, some with power strips and surge protectors, some without, and the same problem occurs. I also tried plugged the receiver into the Automatic Voltage Regulator/Battery back-up surge protector I have for my computer. The "Wiring Fault" light on the power strip doesn't come on, so apparently the outlets I've tried are grounded. I'm going to get one of those electrical testers from a friend to test the outlets directly, but in the meantime I thought I'd post this to see if anyone has any suggestions. Could it be my speakers? They are still under warranty. I also got authorization from Sony to ship it to them--are they likely to send me a new/furbished unit, and is that going to end my problems? Any suggestions would be welome.
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Forgot to mention--the speakers I have are Klipsch Synergy SB-1 (max 75 watts, max 8 ohms impedance, gold post connection), and the speaker wire is 14-gauge Monster XP wire with gold banana plugs. The speakers and wire are as old as the receiver.
Hey man I wish I knew what the problem was. I'm dealing with the exact same problem! :( It was working fine for 2 months, I redesigned my room layout and moved my speakers/Sony STR-DE597 around and now I've got that damn protect mode issue.
Good luck and keep me posted. I'll do the same if I find any answers. ~Aloha, Matt
Hi Folks

I am experiencing the same problem here in South Africa. I bought the same amp in June this year. 4 months later it packed up with the PROTECT message.

I took the amp back to the place where I bought it. They then sent it to Sony's official service provider. 4 Weeks later, Sony have decided to give me a new one.

I am however a little concerned that the model itself has faults and the same problem will therefore occur again. But I'll see what happens a few months down the line with the new one.

Good luck with your problems.
OK, a development. After borrowing a friend's multimeter, I found out my Klipsch speakers were *both* at a steady 4.0 ohms impedence whereas the Sony receiver recommends speakers that have 8 ohms impedence. So I'm guessing my speakers were manufactured improperly or else mislabeled. What I'd like to know now is could the receiver have caused this kind of damage to the speakers? Again, I usually use the stereo for background music--I certainly wasn't taxing the speakers' limits. I was unable to find information on changing impedence online, but I did find something that said most receivers that are rated for 8 ohms can handle 4 ohms, which seems to explain why the receiver and speaker set up worked for awhile. But then should I also be concerned that the speakers have damaged/affected the receiver? I tried the receiver with 8 ohm speakers and it took me a few times before it ceased overheated and going into protect mode. I'm wondering if I should send the receiver--it's still under warranty--just to make sure that nothing's wrong. I suppose I shouldn't mention I was using improper speakers, though that wasn't my fault, nor was it expected from a manufacturer like Klipsch. So I've emailed Klipsch and explained the whole sob story--I'll let you know what they say. In the meantime, check your speakers!
Impedance is a function of frequency. What you are seeing on the meter is nominal impedance. The actual impedance can be as low as 1 to 2 ohms at various range of the human audible tone 20 to 20000Hz. If the speaker has very low impedance at low frequency (40 to 100Hz range), then it can pull a tremendous amount of current from the output stage of the amplifier...even at low volume (like putting a jumper wire across the pos/neg speaker output terminal).

Cheap to moderately priced receivers used to have an impedance switch on the back, which effectively reduces the incoming line DC voltage at the main filter capacitors. This will reduce the peak current delivered to the speakers (less watts). Check your manual for an impedance switch. Some models will require that you press certain keys on the receiver or remote to activate this switch.

A well made receiver (over $1000) will not have this impedance limitation. These receivers are usually rated for 4 to 6 ohms speakers. Check out the high-end Denon, Yamaha, and Onkyo.

Perhaps there is a problem with your speakers. However, most Klipschs tend to be low impedance, high efficiency speakers. The hot spot on the Sony is a dead give away with an impedance issue. The speakers draw too much current from the output stages, causing the heat sink and transformer to overheat.

You can either switch speakers (most el cheapos have a high nominal impedance) or upgrade the amps. Personally, I would dump the amps.
Thanks for the info. Unfortunately, my Sony receiver does not have an impedence switch, and, seeing that I'm a poor grad student, the equipment I have is not top of the line to begin with nor can I afford to buy a different receiver. I can only make do with what I have, I'm afraid. The Klipsch speakers are only about $250/pair--regardless the other models Klipsch makes, the ones I bought are rated for 8 ohms impedence.
If $ is an issue, then I would definitely go with the Technics/Panasonic/Matshushita receivers. They are very competitively priced, with good output transistors. These may work well enough with the Klipsch speakers. Less bells and whistles...more robust internal components.

The pricier Sony ES line is also acceptable for most average speakers.
If your amp is cutting out even at low volumes, then i dont think the Ohmage of the speakers would make any difference as the volume is just too low, I presume you have checked the cabling for any dodgy connections. Failing that you might want to reset the unit as another problem can be down to the software on the receiver crashing, try resetting the amp and test again.

Also look at the obvious is it overheating, check to see if its hot enough to cook eggs on, check the air curculation around the unit. Is it full of dust causing it to overheat?

Hope this might help
This message has been edited since its posting. Latest edit was made on 03 Jan 2005 @ 5:45
Another development: I got an email back from Klipsch. They told me the 4 ohms reading on the Klipsch is probably just the woofer, which I didn't know (I was only testing the leads, as was Best Buy):

"The impedance of our most affordable and smallest Synergy Series SB-1 bookshelf speakers are 8 ohm nominal. Impedance changes up and down with frequency. The DCR impedance that someone may have measured just off of the speaker leads themselves on the back of the speaker, would only be reading the woofer impedance only (which is likely to be around 4 ohms) and would not have measured past the crossover taking into consideration the impedance of the tweeter as a whole, the SB-1 is therefore an 8 ohm nominal speaker."

Yet when I tested some cheap 50 watt max 8 ohm speakers on the receiver, after a few tries the receiver worked fine--no overheating or going into protect mode. The impedence reading from the leads of these speakers was 8 ohms, however. Now I'm confused. Would this be a set of speakers without a crossover or a different kind of crossover? And does this mean that the receiver doesn't like crossovers or certain kinds--that both woofer and tweeter would have to be rated at 8 ohms? Is that normal?! I'd appreciate any info on crossovers or nominal impedence and if this would have any effect on the receiver.
I will try resetting the unit again. Fairly sure I did this once, but I guess anything is worth a try.
If there is a tweeter and woofer, then there will be a cross-over network inside the speaker. Per my previous post, the low impedance woofer will drawn a lot of current at the lower frequency. This will cause the amp to overheat. The high impedance tweeter doesn't use a lot of power (no movement of the cone).

In general, the impedance of the woofer will determine the nominal load presented to the amp. Why? Because low and mid-range frequency are much more dominant in audio materials. A high frequency driver does not have to move a lot of air to be loud. Therefore, the NOMINAL impedance of the speaker may be 8 ohm (combined impedance of low and high frequency drivers), but the actual load to the amp is closer to 4 ohm.

Klipsch cheated by publishing 8 ohm, when it should have been 4 ohm. You can either change to a more robust Technics amp or stay with the cheap 8 ohm speakers.
Thanks again for the information, furballi. I did try hooking up the second set of speakers with the Klipsch speakers (one as the the A set and the other as the B set) in order to distribute the load on the channel, but the receiver was still overheating and going into protect mode. Thought I could also add a subwoofer, but learned that the subwoofer would be on its own channel so I'm guessing that wouldn't help any.
Adding 2 more speakers to the B outputs will lower the impedance of the load to about 2.7 ohm...ohm's law.

You're NOT going to fix the problem without changing the amp and/or the speakers.
ya know, I'm really going out on a limb here, but I had pretty much the same problem with an older model str reciever (bought from best buy) went through the same trials as you did, then said f-it, I'm buying a denon. No seriously, replace ALL your speaker wires, and with good 10 or 12 guage, not the thin crap. I actually had atiny, but still barely visible "burn" mark,INSIDE the sleeve of one wire going to a tiny rear speaker. Enough to throw it into protect mode. Try it, trust me. Good luck.

...and the dead shall walk the earth...
Ok, I've got the same problem, my unit is also about 4 months old, and I got mine from Radio Shack, I could NOT tell you what ohms my speakers are as they are all different and a friend from WA came down to install the system, I was very pleased with the system till recently, At first it did that protect thing once when I had the system quite loud, then after that it started getting more frequent, and now it's IMPOSSIBLE to watch a movie as the unit only works for about 20 mins. I really don't think I could hook this thing back up even if I did send it in to be fixed or bought something else.

Here's what I've got...

The receiver is set up as the "brain" as my friend said, so I guess my system is brain dead.

I've got an older Onxyo (sp) amp driving the subwoofers, there are speakers hooked up all over the place and my dvd, vcr, cd changer and tv are all plugged in, it took my friend like 3 hours to hook everything up,

All the wires are new, nothing cheap, we even bought gold banana clips for the wires.

I'm at a loss here, short of buying my friend a ticket down here to have him fix it.

Please help.

Mark Ruiz
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