Speakercraft MCZ88 problems - AVS Forum
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post #1 of 5 Old 07-30-2009, 08:32 AM - Thread Starter
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Can anyone make some suggestions to me on what else to try? We have had a system installed with the main receiver being a Speakercraft MZC88 their control key pads and speakers. It was installed by a guy I know who has done many of these in the past with the exact same units used. We are now waiting on the replacement of the third MZC88 in two months. The first one died after about two weeks and we were told Speakercraft said it had a bunch of blown fuses inside. The second and third units just stopped having sound #2 lasted about 10 days and #3 lasted about 3-4 days. The installer has us with sound using a temporary back up Harmon Kardon but not being able to change cable stations without going into the electronics closet and just pure frustration is killing us. They have run many test ie OHM rating on each speaker, a speaker, keypad and wire continuity test as well as each key pad. We have a APC1500 battery back up and surge protector and had a electrician install a dedicated power line to the closet. The closet gets warm but not hot and is well ventilated. What else can we try, test or check? We have been using a ipod most of the time for our source and the last time it worked until I turned it off then the next morning the sound was dead. I am going nuts any help would be really appreciated. Thank you in advance. PGG
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post #2 of 5 Old 07-30-2009, 11:17 AM - Thread Starter
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They sent this below my installer this today by email it chaps me hard since they dont suggest a "device" to cure the supposed problem. Is this a common problem to burn up units when voltage gets in the 110-112 range? Of course we have no idea if that has even been happening. Thanks PG



Battery back-up is not what we're looking for. That would protect in
the event of a power outage. We're mostly concerned with dipping line
voltage - we have seen problems specifically with line voltage that
dips down to the 110-112 volt range. A device that keeps the line
voltage steady at or near 120 is what we're looking for.
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post #3 of 5 Old 07-30-2009, 01:29 PM
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Ask them how the fuses could have blown if line voltage dips. Bet they don't have the answer to that.
As for devices with such critical voltage requirements - if thats the case - build a voltage regulator into the unit - however it sounds more like an installation screwup.

When all else fails - RTFM!

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post #4 of 5 Old 07-30-2009, 02:31 PM
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Quote:
Originally Posted by Knucklehead90 View Post

Ask them how the fuses could have blown if line voltage dips. Bet they don't have the answer to that.
As for devices with such critical voltage requirements - if thats the case - build a voltage regulator into the unit - however it sounds more like an installation screwup.

I am not an EE but it is my understanding that when voltage drops current (and the resulting heat) increases, and that can be a real problem.

As for the original question, I am not familiar with Speakercraft but the fact the Harman Kardon receiver has filled in without problem tells me that maybe they need to consider another brand from a company that knows how to build reliable receivers, and find another solution to the switching issue.

"The truth is out there!"
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post #5 of 5 Old 07-31-2009, 08:21 AM - Thread Starter
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Thank you both for your post and thoughts. Here is what someone else had to say about the problem. Thanks PG

Oh dear, where to start?

First of all that APC 1500 is not the problem. I have two of them and they will support voltage in 1 to 5 msec. So forget that as the problem.

With three units having failed then there is something wrong with your installation and or application.

I have pulled the 50 page manual on that unit off line.

First ventilation. It states that the unit must be on top of all other units, and if installed in a closet there has to be forced air extraction.

I need very great detail about your speakers and how they are wired. There may be a serious installation error, which on a forum can only be analyzed with great detail about your installation.

Now those units are very much in the nature of background units.

They contain 16, 50 watt amplifiers. However the max power draw of the unit is 275 watts.

The unit is specified to give 50 watts to 8 ohms, or 70 watts to four ohm loads, only two channels driven. This would give a conversion efficiency of 50%, which would be fairly typical. So you have only 135 audio watts to divide between 16 channels, which is about 8 watts per speaker channel if all are driven. Actually I see looking at the manual, the amps give 1/8 rated power all channels driven, which is 6.25 watts per channel.

It states in the manual, that this unit is not intended for high power application.

If you want to have more than one room playing at more then low background volume, then external amps are required for each channel driven from the preouts. That will get very expensive.

I'm certain you will have another unit blow, if the installation and use is as you have it now.

So to help you further I need to know precise details of the installation, especially wiring details, speaker specifications, speaker numbers and details of any room controls. I need to know how many of the sixteen amp channels are in use.

I also need details of how you have used this unit and intend to use it.
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