@gottfrieds28407 thank you for your reply.

...whether it is the small-signal circuit or the power amp ?

you can find out by disconnecting or shorting  the preamp output

Without the LFE cable connected, there is no noise. Same if the AV receiver isn't sending anything.

i found the bad stage by measuring DC voltage at the op amp outputs

or you could isolate the bad stage ...

Ah, so there are multiple stages I can test to isolate the issue? That is helpful. I do not know how to tell where the stages are on the PCB, though.

can you read the resistor values ?

It's hard for me to read the resistor stripes because they're so tiny, but at least the resistors covered by the sealant are correct. All the other resistors have sane values in the 1-20kohm range.

maybe you could send me a pic of your amp ?

I took pictures: https://overflod.chary.us/static/as60cx-... You can see on the front-right photos where the sealant is spilled. Maybe a helpful step forward would be if you could point out where on the PCB I can test each "stage".

Thanks,

Zach

Nice guide. I'm having the same symptoms (sub sounds noisy/rumbles) with the Canton AS 60 CX, which I thought was similar to the AS 60 SC, but the PCB is completely different. I bought it used and it has always had this issue. There is the same sealant spilled on some of the resistors; however, a multimeter shows the affected resistors having reasonable values in the 5-14 kilo-ohm range. I also tested the capacitors and they seem to charge/discharge normally. @gottfrieds28407 could you please offer any advice that could help me further diagnose this on the AS 60 CX? I am not overly familiar with audio electronics but I do know my way around simple circuits.

Other things I tried:

- Switching LFE cable to Left instead of Right/Mono

- Checked voice coil/surround/cone - looks healthy and intact

- Every permutation of sub settings on my A/V receiver