Marantz Dolby 6.1 right channel fritzed--HELP! - diyAudio
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Old 4th June 2004, 03:09 AM   #1
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Default Marantz Dolby 6.1 right channel fritzed--HELP!

My mother recently blew the right channel of her 6.1 Marantz home theater receiver last month and I have dismantled it and am ready for diagnosis and repair. I will post pictures in my next post. I am wondering if anyone can tell me where on the mainborad I should start my diagnosis. Experience tells me to start with the transistors by measuring for any inconsistencies and then to do the same with the main capacitors (huge 1000 mfd caps). She blew the right channel by letting the + and - wires touch at high volume and now all that comes through the speaker is a faint hint of sound (almost like playing a blown speaker). I would be every so grateful if someone could offer me any advice on the matter. I have a multimeter that I am somewhat familiar with but could use a little help as is apparent. Thanks in advance.
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Old 5th June 2004, 07:45 AM   #2
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Is there still a warranty left on the thing?

But wait, that would not be the DIY thing to do would it
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Old 5th June 2004, 10:42 PM   #3
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Nope, warranty expired last year.
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Old 6th June 2004, 07:19 AM   #4
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Here is a bird's eye of the main board, I have circled the sections I would focus in on. Anyone have any direction for me to go on this? I will post another picture of the transistors on one of the channels. I want to test the two huge capacitors to make sure they are both good. How do I test capacitance?
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Old 6th June 2004, 07:21 AM   #5
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Here is the picture
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File Type: jpg mainboard view 2.jpg (73.9 KB, 136 views)
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Old 6th June 2004, 07:26 AM   #6
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Here is the view of some transistors on one of the channels. Whenever I have had blown amps it has always been the transistors. Anyhow, how do I test them? Can they be tested on the board?
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File Type: jpg transistors.jpg (68.5 KB, 125 views)
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Old 6th June 2004, 11:11 AM   #7
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I think you are looking in the wrong places. If it's a 6 channel amp there should be 3 output module/chips at the very least (assuming 2 channels per chip). 6 pairs of transistors if modules/chips are not used. Where is the main heatsink? And what is attached to it?

IMO it's pointless looking at the PSU caps - if there was a problem with them it would affect all channels.
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Old 6th June 2004, 04:56 PM   #8
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I think you are probably right. As you can see, I have removed all of the other boards from this mainboard so I could have access. Which board should I be looking at? I will post another picture after this one of the base unit with the main power supply.
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File Type: jpg all boards.jpg (46.1 KB, 101 views)
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Old 6th June 2004, 05:17 PM   #9
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I believe this is what you may be talking about. There are six sections respective of the six channels and a huge heatsink for all six channels (as per your description). How can I tell which section is the right channel? Which components should I test when I find the right channel (resistors, diodes, caps, etc)? I don't know if this helps in diagnosing but sound still comes through the right channel it's just that it is muted almost to nothing and sporadic on the sound it lets through.
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Old 7th June 2004, 05:43 PM   #10
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Can you trace from the output terminals for the blown channel back to where it connects to that board mounted on the main heatsink?

I suspect just-functioning output transistors. You can diode test them in situ, but I wouldn't bother as they will probably read OK. If you really want to check them, measure all the other ones as well and compare readings. You may have a tough job hunting down exact replacements... They will probably be 2SCxxxx and/or 2SAxxxx devices.
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