Marantz SR7300 and Protect Mode

maolen · 05-23-2003, 05:50 AM

Hi,

I am an owner of Marantz SR7300 since December of last
year. I am very much satisfied with it's sound both in HT
and HiFi. However, when I watched LOTR (2 towers) DVD,
my unit went into 'Protect Mode' at least 5 times during
the whole movie. When it goes into protect mode, sound
will be cut off for about 5 seconds.

I do not understand why this happened when my volume
is only set to -17db. This happens when there is a
sudden burst of sound. Although the sound is not very
loud, it seems the sound has much bass. I feel this
Protect mode is unacceptable in this volume level.

After a few trials trying to simulate, ff I found out.
Note: am always simulating the exact scenes where it 1st
went into protect mode
1. After pressing reset buttons (back to factory settings)
I can play it at around -10db but any thing lower will
go into protect mode
2. I set my speaker to small, I can play at -5dB volume
3. Switched off the unit (power cord not plug) for 5 hrs,
I can play the unit at +7dB (did not try higher as
volume is already loud)
4. Allow unit on standby for 3 hours, I can again play it
only at -10dB. It seems the longer it is on, the lower
volume I can play.

I have brought the unit at Singapore Marantz dealer and
they found no problem with my unit. Technician and
Salesman told me that my speakers could be the culprit
as the power sent by the receiver is high which my
speakers cannot cope and to protect my speakers from
damage, the receiver goes into protect mode.

I tried other movies and the same happens to some while
others are ok. music cds (using analog), the protect
mode only kicks in when the volume is too loud, about
+10dB volume.

I cannot accept that this unit will go into protect mode
at such a low volume but what can I do? Can anyone who
has the same receiver (and speakers if possible) to
try if the same will happen? I feel very helpless and
am starting to think that my purchase is not good.

Oh, my speakers are all bookshelf
Mains: Kef Q1 (91dB sensitivity and 8ohm impedance)
Center: Kef Q9c (91dB and 8ohm)
Surround: Kef Cresta2 (90dB and 8ohm)

Any help and suggestion will be appreciated.

maolen · 05-26-2003, 11:29 AM

any help? especially from SR7300 owners....

John Garcia · 05-26-2003, 03:36 PM

Maybe you can ask the store you bought it from to swap a new one out for you, since the service center could not figure it out. Did the service center tell you what things would put the receiver into protect? I have had my 6200 for 2yrs, and I have never had this happen, even with the volume momentarilly at +15. My typical listening level is between -20 and -15, with ref calibration at -8.

One remote possibility is that one or more of your speakers is damaged and causing this. Try hooking up each of them one at a time to see if it still does this. A damaged driver(which should be obvious) may cause this type of intermittent problem.

maolen · 05-28-2003, 08:32 AM

Hi John,

Swapping with the store is not possible here. HiFi stores here normally do not have 1 to 1 exchange policy.

The technician and salesman told me that my speakers cannot take the power I am sending and that to avoid frying them, the receiver goes into protect mode.

I'll try your suggestion to try one speaker at a time. Hope to find the problem. At least if it's one of the speakers, I know what that it's the speakers causing the protect mode unlike now where I am stuck to the problem and nowhere to go.

Jonathan M · 05-28-2003, 05:12 PM

Hi maolen,

A receiver will only go in to protect mode if it gets too hot or if it suddenly finds itself driving a set of low impedance speakers at too high a level. This causes the voltage rails to droop which kicks the protection circuit on. Based on your experience, perhaps this is heat related. Where do you have the unit - does it have adequate ventilation around it?

The salesman is incorrect in saying that the receiver is shutting down to prevent damage to the speakers - the receiver knows nothing about what your speakers are doing except their impedance and the back EMF produced.

Do you have a sub? If so, all speakers should be set to small. The Kef's you have cannot produce adaquate bass below 80Hz no matter what their specs sheets say.

The Kef's impedance may also drop fairly low (4ohms or so) between the port and driver resonances - this may be causing the receiver to shutdown.

Your best bet is to improve ventilation for your Marantz, check and recheck your speaker cable connections at either end (speaker and amp), set all speakers to small and recalibrate.

Also, how are you watching LOTR: TTT? Is it an illegal DVD?

**HTF Ads**

ChrisWiggles · 05-28-2003, 07:06 PM

This unit should not be doing this. It could be the speakers are blown, thus creating a slight short which sucks power, which the marantz should shut down in response to. Could be something simple like stray strands of wire at the terminals. And of course, heat is an important concern, make sure you have PLENTY of ventilation, and that the unit is not too hot to the touch.

Jon's advice is spot-on. If everything checks out, and the speakers are not the culprit, then take the unit back to the dealer to be fixed/exchanged. And if all speakers are set to small, and it's STILL going into protect mode, it's probably something more than just heat. There has to be a short somewhere...

maolen · 05-31-2003, 12:38 PM

Thanks to all who replied.

I have tested it out again today but only for a short while and will re-test again later. What I did today is plug the unit in a different socket from the rest of my appliance. What happenned is I can now play those specific scenes upto +1dB.

Jonathan, my unit is on top of my rack and the rack is around 1.5feet away from the wall. What is 'back EMF produced'? I do not have a sub but I also tested with all speakers set to small but it did not solve the problem. I am planning on buying the KEF Q7 (floorstanders) in the future (after few more months of savings) but if the problem is caused by low impedance, does that mean I need to reconsider other speakers?

ChrisWiggles, I tried using my surround speaker wires and connected them to my mains and the same still occur. I really suspect that something is wrong with my unit that's why I brought it for service but the technician said all is working fine and that using their speakers does not show the problem I have. Now I am stuck with this problem and no where to go.

ChrisWiggles · 06-01-2003, 01:28 PM

Yeah, while +1 is still quite loud, this unit should not have a problem with it while set on small. Why can you not take it back to the dealer/tech?

And the other important thing you've not checked is the speakers. There may be a bad speaker somewhere that's had a melted voice coil, thus causing a short-circuit which will surely drive the Marantz into protect mode. Seeing as how it does not happen except for high volumes, there still might be enough resistance in the coil such that it plays except for extreme volumes, when the low resistance really begins to suck too much power. While I am often skeptical of many so-called "techs," there was no problem with the receiver when you had it checked out, which leads me to beleive that it's something else, such as heat, the speakers, sloppy speaker wire connections, or it could still be the unit and the tech could have been incompetent or missed the problem.

You should try swapping around your speakers. Play two-channel music full-range on your mains, does the unit go into protect? Do the same thing with your surrounds. If it does start going into protect on one particular pair, then you probably have a damaged/faulty speaker. Try narrowing it down like this if you can, or take them ALL into your dealer to have them checked it. We still have not determined whether the problem lies with the amp or somewhere else, but again i want to point out that when you had it checked out, they played your marantz on different speakers and there was no problem, so at this point I recommend you spend some time troubleshooting your speakers, or just taking them all into your dealer. You might also try measuring the resistance across each speaker, if one is particularly low, that one is probably faulty/damaged.

maolen · 06-08-2003, 06:33 AM

ChrisWiggles,
I can take it back to Marantz dealer here but it'll be pointless since they are saying my unit does not have a fault and that it's normal for SR7300 to go into protect mode.

After several trials, I can see that the point where protect mode kicks in is not always the same. Sometimes it'll kick in when past +5dB but sometimes even at -5dB.

I noticed that whenever I power on my unit, I can crank up th volume to maximun (+18dB) w/o any problem. But after sometime, say 2 hours of playing, when I try again same source I could not reach maximum again ang the unit will go into protect mode on varying volume but normally above 0dB.

I tried w/ only Main Left connected, then main Right, then centre and all are going into protect mode at the same point. This eliminates the possibility of one speaker or some wires being faulty. I really could not understand why I can go into maximun but after sometime of use, it does not allow me.

I want to bring my unit again to the dealer but am pretty sure the same will come out.

maolen · 06-10-2003, 11:19 PM

PeterCB · 06-11-2003, 09:52 AM

maolen,

The 7300 should definitely not go into protect mode at -5db or less. Your dealer telling you that this is normal is incorrect.

As you may remember, I also have a 7300. I got mine a little before you did. My front speakers (left, right and center) are all large Definitive Technologys, with a nominal impedance of 4-8 ohms. I always play movies at -5db, and have never had the receiver go into protect mode. It has only gone into protect mode once in the 7 months that I have owned it, and that was when playing some very bass heavy "party" music at around +5db.

The fact that your shutdown problem only occurs after the receiver is on for a few hours leads me to think that it is probably heat related, although it doesn't sound like you have a ventilation problem.

I would definitely take the unit back to the dealer. If he is not willing to replace it (which I can understand after six months), then have it repaired under warranty. You paid top dollar for a properly functioning product. Yours is not. That's what the 3 year warranty is for.

Peter