Problem with marantz 7200. Something blew (i think ??) - diyAudio
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Old 13th December 2008, 05:42 PM   #1
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Default Problem with marantz 7200. Something blew (i think ??)

hello all,

my first post here. requesting for your assistance.

have a problem with my marantz pm 7200 amplifier.

amplifier was on when an electric iron was plugged into another outlet. the inverter shut down and restarted. heard a sound from the equipment rack but could not figure out which unit made the sound.

then on playing music, i find, that the volume levels have dropped drastically. i need to position the volume at 12:00 clock position, which is normally unbearably loud. normal volume position is around 8:00 to 10:00 clock position. the bass is also much reduced.

however, both channels ARE producing music. there is no hiss, crackle or any other interference.

opened up the amplifier, but could not see anything specific that looked damaged. my friend says either one of the fuses or one of the output stages could have gone kaput.

need your opinion guys, before I take it in and have it looked at.

additionally, as a matter of curiosity, when I opened it up, it did not look to be like a dual-mono design. however, in most places on the net, including some marantz sites, this is advertised as a dual-mono amplifier. I am attaching a pic of amp internal. What do you guys think this is ??

thanks in advance. eagerly awaiting your inputs.
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File Type: jpg marantz_pm_7200.jpg (62.9 KB, 236 views)
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Old 14th December 2008, 08:22 AM   #2
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guys...

some help please..i need to take it in this week. i'd like to have an idea of what this might involve.

looking forward to some responses.

ciao
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Old 14th December 2008, 09:43 AM   #3
Bonsai is offline Bonsai  Taiwan
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Another Marantz amp that's kissed its *** goodbye.

This is truly abominable.

Wh t happened to th e good old days of Marantz quality?

I guess once Philips bought them, it was downhill all the way.

Clearly Dennon have done nothing to try to rectify the issue.

Lets all spread the word: Marantz is JUNK.

Maybe the owners will try to sort it out then.

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Old 14th December 2008, 10:14 AM   #4
jitter is offline jitter  Netherlands
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@Bonsai: I find this a rather baseless remark. Yes, I have had Marantz equipment that failed, but no more or less often than other brands I had or still have.
Sudden mains failure can damage any equipment attached to it. I've seen it happen to very expensive measuring equipment. Doesn't matter what brand is on the casing.
Please, refrain from throwing mud on this forum.

@diy_lost: the power supply is the first thing I'd go over considering what happened. Measure all power rails to check if they're still working properly.
If the sound you heard was a click, it might just have been the speaker relay falling off.

Did you try other line inputs? Did you swap the speakers to channel B?

About the dual-mono thing: audiophiles usually only consider something dual mono if both channels are built up completely separate from eachother (often including the power transformers). In essence stereo is dual mono, so the term dual mono might be 'abused' a little for marketing purposes.
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Old 14th December 2008, 04:43 PM   #5
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jitter,

thanks for your suggestions. will try checking other inputs as well as Speaker B and report back.

ciao and thanks again.
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Old 14th December 2008, 04:43 PM   #6
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jitter,

first off, to clarify on the nature of the sound I heard. It was not a click, more like a *phat*.

I did the following tests :

1. Connected speakers to "Speaker B" outputs. no difference.

2. Connected RCA from CDP to other inputs (Aux1, Aux2). no difference.

3. Connected my Ipod to Aux2. no difference.

The problem still remains. Volume is drastically reduced. In fact I could take the volume knob to 2:00 clock position. It was just comfortably loud. Normally I could never do that. In fact I have never taken it that high in so many years of using the amp.

To re-iterate :
1. Drastic reduction in volume levels is the only problem.
2. Left and Right output is still perfectly okay, in the sense all the musical information is being reproduced.
3. There is no other static, hissing or other interference noise.
4. Also the traditional click and thump when the amplifier is started is also there.

With respect to the other thing you wanted me to check :
Checking power rails :
I regret to inform you I am a total ignorant in this field. However, if you can guide me step by step and tell me the tools I will need to test, I wil go about acquiring them and follow your instructions to test the needful. (My username is diy_lost !!! is it not clear ?? )

do let me know how I proceed next.

Thanks again for your help.

ciao.
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Old 14th December 2008, 08:18 PM   #7
jitter is offline jitter  Netherlands
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IMO a phat-sound could indicate that a component blew up. Usually this is accompanied by a little smoke and a bad smell, but not always.

To check the power supply circuits you need a (digital) multimeter set to measure DC voltage. But don't go running off to the nearest electronics store to get one because although I'd gladly talk you through it, I am unfamiliar with this amplifier. Therefore I won't be able to give you specific instructions on where to measure what value.
That means you have to find the power supply circuits and determine if they still function correctly on your own, which might be a bit difficult for someone without knowledge of electronics.

I'm sorry, but this is where my ability to help you falls short. Good luck anyway.

One last tip: check if the fuses are still in one piece.
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Old 15th December 2008, 07:37 AM   #8
Bonsai is offline Bonsai  Taiwan
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Jitter,

no. Its about time consumers let rip on poor quality products. Marantz have no excuse on this one - zero.


I've had a CD Recorder which stopped working 1 week after it came out of warranty and they refused to fix it (Philips).

These companies make bad quality products and then expect consumers to take on expensive 'warranty extensions' to pay for sloppy design and engineering.

In my view, there needs to be some legislation against this nonsense - its exploitation plain and simple.

I will not be buying a Marantz product anytime soon I can assure you and if anyone asks my opionion, they will get it straight. Ditto a few other brands with the same problem.
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Old 15th December 2008, 08:06 AM   #9
Mooly is offline Mooly  United Kingdom
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This doesn't make sense unless I have missed something along the way.
Does the amp have remote control ? Whatever has happened it doesn't sound like an output stage problem, they don't fail like this - the gain changing etc and certainly not on both channels.
You run it off an invertor ? Mains voltage to the amp OK ?
If it has remote what functions can you control. What I am getting at is whether there is any electronic gain/muting/tone etc.
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Old 15th December 2008, 08:07 AM   #10
Mooly is offline Mooly  United Kingdom
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And if there is, does it have a backup cap/battery on the EEPROM or microprocessor that you can disconnect to reset it all.
Assuming it has all this of course
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