marantz sr6012 no sound

[oshimapt]

hello guys,


first of all i'm not a qualified repair guy, i am a diy guy and as years pass by i have some experience on repairing eletronics, and i'm hoping someone can share their experience.

i have a marantz sr6012, some times it turns on and works normal, but after a while the sound cuts off or it starts getting distorted and then cuts off.

when this happens there is no audio no matter the source used, and the OSD shows unknow audio signal from the source.


i was reading very carefuly the service manual and it is all pointing for the digital audio block, witch is very complex of course. there is a ic, the IC221 that by the diagram is responsible for all the audio routing and control.


i've put the unit on diagnostic mode and select the analog audio block and no sound from the speakers or pre-outs. so i think even when using pure direct and analog as source it somehow still needs some control from that IC (or other) to operate the analog swiching ic NJU72750AV and the volume ic NJU72343V.

so i started trying to get some measurments and i found that i have 1.8V and 3.3V supplying the IC, so this end is working ok. i will try to scope them to see if there is any kind of ripple messing the IC stability. (order a dso138 scope so i will be waiting for a few days).

i also measured the input signal for that ic and it all showed 1.2V, wich i think is to be expected.


on the pic attached the red circle is where i measured the supply voltages. on the other side of the board there is 2 IC that are converting the 5.2V from the smps to 3.3 and 1.8. the orange circle is where the IC 221 is located.

this is the link for the service manual:

Elektrotanya for electronics experts

Electronics forum for electronics experts to repair defective appliance.

elektrotanya.com

all the relays click and the unit never enters on protection mode.


i didnt had time to do more testing, so this is what i have for now and hoping some of you have stumble on the same issue with other Denon/marantz avr. i think they all work the same way, they allways have some IC that controls all the audio routing, and solution might be the same.

 

[oshimapt]

hello guys,

here is an update:

saturday morning i was doing a more stricted inspection and i saw 2 resistors, that were looking like they had some kind of corrusion on them, R2238 and R2245. measured them and one was givem readings on the Mohm and the other was not giving a reading at all. i think their primal function is to protect the IO of the IC.
anyway, gave them a good cleaning with cotton and alcohol, tried to reflown them with my tinest solder iron tip and cleaned again and let it dry a litle.
measured them again and they both gave readings, not the best but WAY better.

turned on the receiver and BAHM, sound coming out from the speakers

bottom line, if some one have a D/M receiver and is trying to repair, they always have a IC that is responsible for all audio rounting and control, even analog inputs. check really well if all the surrounding circuiting and make sure the is IC is ok.


really hope this experience of mine can help someone that is on the same pinch as i was.