Marantz SR5012 popping and other sound issues

[acedogblast]

Hello I have a Marantz SR5012 7.1 AV receiver that is producing speaker pop and other sound issues. These sounds are coming out of all connected speakers regardless if they are configured to be used. The rca preouts are clean from these defects so I am assuming the problem has to be with the amplifier.
These sound issues are random and unpredictable. There are times where the unit can go 10 minutes without any problems then suddenly the problems come back. It doesn't seem to matter if there is sound being played or not.

I have disassembled the unit and was able to take out the "7 CH AMP B'D MP" PCB. From what I can see there doesn't appear to have any obvious problems. I have check the large transistors connected to the heat-sink and none of them have any shorts. This makes me believe that problem is elsewhere. Taking a look at the service manual on p31 the positive and negative voltage to the amp board is provided by the main board which is what I am now trying to take out. I suspect that the problem is there with the power regulation. Do any of the experts here have any ideas?

Marantz SR5012 Service Manual: https://cdn.badcaps-static.com/pdfs/...c775c5d540.pdf

Also additional note: I notice that the 2 subwoofer preouts are just split of a single output line on the preout board. I though Marantz advertised this as a "7.2" AV receiver?

[petehall347]

Re: Marantz SR5012 popping and other sound issues

all channels points to power supply . maybe a transistor .

[acedogblast]

Re: Marantz SR5012 popping and other sound issues

OK I have a big update on the repair. Quite a lot has happened.
Firstly whoever designed this receiver decided that it is OK to connect PCBs together with smaller PCBs with fixed connectors. It was a big pain in the ass to disassemble this matrix of circuit boards. For anyone who needs to do this a very useful tip is to use plastic prying tools and a very small and thin flat head screwdriver to stick in between the connections and then push apart the connectors on both sides. The most difficult part to remove is the preout PCB which is the PCB with all of the RCA connectors as shown here:



As you can see it is between 2 other PCBs. The trick here is to remove both the preout PCB and the input PCB as a whole. The input PCB is the PCB between the PCB with a row of capacitors (This is what Marantz calls the HDAM) and the input PCB on the left side of the picture.

One thing NOT to do is to use a metallic object such as a screwdriver to pry the PCBs. How do I know that you ask? Well this can happen:



So yea I just dented the PCB and disconnected one of the traces on the edge of the PCB. To repair this new damage I first tried to solder them back together but was unsuccessful. So I had to resort to making a new connection with a wire to the luckily only one connection where that damaged trace goes. This is how it ended up:



With that done I finally was able to get to the main PCB where I suspected the original problem was. Nothing was obviously damaged until I removed the main PCB out of the case to take a look at the bottom. (I envy you people who only work on old audio equipment with a bottom access)

This is what I found:



There is some sort of oil coming out of the transistor with the text "KIA 7905PI". Looking this up on Google tells me that this is a linear voltage regulator. Some of the other regulators also has some oil on them so I plan to replace all of these including the full bridge rectifier.
I suspect excessive heat on these components is what lead them to fail. If someone also has a similar issue you can check these components out by just removing the AMP board and the front cover. You also might be able to replace them too without having to go though the pain of total disassembly like I did. Here is a better picture of the front of these components:



So my question to you experts here is should I replace them with the exact same brand/model or should I get something from a different brand with same specs and hope that they would be better?

[mmartell]

Re: Marantz SR5012 popping and other sound issues

Not an expert but...

What makes you think those voltage regulators have failed ? Wipe them off and look for a crack where this oil is coming from but I'd doubt they're leaking from the inside.

If you're intent on replacing them any 7805/7905 will do.

Those shitty plastic edge connectors you are ranting about are enough to cause random noise. If I had seen this sooner I would have advised you to WHACK! the side of the receiver while in operation to see if you could force it make noise and/or become nice and quiet.

[petehall347]

Re: Marantz SR5012 popping and other sound issues

its not oil . its for thermal contact . similar to the white stuff that's more widely used .
those devices dont contain liquid

[acedogblast]

Re: Marantz SR5012 popping and other sound issues

If these voltage regulators are not the cause of my problems where else could cause the popping noise?

[frankusb]

Re: Marantz SR5012 popping and other sound issues

Can you describe the sound more? I had an Onkyo that would emit what I would call digital noise that needed the power supply capacitors replaced on the HDMI board that does the digital sound processing.

Do you have a pure direct option that you can try to remove the digital domain?

[acedogblast]

Re: Marantz SR5012 popping and other sound issues

Random Speaker popping noise. Occasionally happens every few minutes. Sometimes buzzing. Volume setting does not make any difference on the noise. It occurs on all speakers but not when using the preouts. Therefore I do not think this has to do with anything digital but with the amp circuit.

[acedogblast]

Re: Marantz SR5012 popping and other sound issues

Can now confirm that these regulators are not the problem as I have removed them and tested them to find out they are all good. Any suggestions on where to look next?

[stj]

Re: Marantz SR5012 popping and other sound issues

the high voltage power to the amp transistors is probably where the problem is,
if it's not a bad solder joint then it could be an intermittent connection inside a capacitor or even a cracked wire in a fuse.
on that subject - pull any fuses and make sure the spring contacts arent loose.

this may be a good time to ask what test gear you have?

[mmartell]

Re: Marantz SR5012 popping and other sound issues

If these voltage regulators are not the cause of my problems where else could cause the popping noise?

Those shitty plastic edge connectors you are ranting about are enough to cause random noise. If I had seen this sooner I would have advised you to WHACK! the side of the receiver while in operation to see if you could force it make noise and/or become nice and quiet.

This is not a random guess on my part I had it happen to a Marantz SR5008 of mine.

[acedogblast]

Re: Marantz SR5012 popping and other sound issues

Ok so I have looked over the entire unit can couldn't find anything that was visually damaged. I did reflow the large capacitors on the main board and reassembled the entire unit hoping that would do something and fortunately the loud and random popping is gone. Either the reflowing the solder fixed a bad connection or the fixed connectors on the PCBs got a better connection with a reseat.

Unfortunately a new problem has arisen. If I adjust the volume too high the AV receiver shuts down with a blinking red led light. I think this is the receiver going into protection mode. Another minor issue is that the all surrounds have a quiet hissing/buzzing sound but the FL, FR, and center channels are quiet. Not sure what is going on now but at least this is a step in the right direction. Looks like I have to reopen the receiver. Hopefully I don't need to take the Main board out again.

EDIT: Checked the protection history and got an ASO code.

[acedogblast]

Re: Marantz SR5012 popping and other sound issues

Found a repair blog for a SR7007 (https://alpengeist-tvrepair.blogspot...g-rapidly.html) and was following the diagnosis. I have checked all of the resistor reading from the base of Q405 which is the main transistor that triggers the ASO detection to each of the 7 channels 22K resistors and found that all of them had the same reading around 21.5K ohms.

[acedogblast]

Re: Marantz SR5012 popping and other sound issues

New update the receiver now goes into protection mode right on start up with no speaker connected. Going to reinspect the AMP board and checking voltages.