diagnosing a silent sound system

azureblue · Post by **azureblue** » 14 Jul 2023, 13:15

There is no sound from radio, CD, etc. and Nav. When I start the car, I hear a pop through the speakers. So I assume there is power to the power amp.

I got a indy mechanic's scan, and his scan reported codes coming from the AUD (audio?) module - open circuit on almost all speakers, but still no sound. He did hear the pop which the sound system came on.

A search ID'd the AUD as the power amp as PN 36013556, but there seems to be 3 models of this.

I checked the speaker connector and made sure the pins were in place. No problems there. I reset the sound system and got some faint audio from the rear speakers, but that's all.

azureblue · Post by **azureblue** » 15 Jul 2023, 08:56

PS - so it's the power amp. Which I read is keyed to the car. Question - Isn't this a Harman Kardon sound system? I found a vid that shows MOSFETS, so I think it could be repaired. Or maybe the circuit board that has teh code key on it can be swapped with a used amp.
Any input / advice?

azureblue · Post by **azureblue** » 17 Jul 2023, 07:53

OK, here is what I have found out so far:
The unit is HK, but Mitsubishi makes the electronics
A breakdown:
Audio module HW3140904 AA (and this swaps with several otehr Volvo power amps)
Suppier code U910A

PC Board codes:
The driver board----
PCB – DSP
N931L827
N211J30110
The power amp board ( with the MOSFETS) -----
PCB -Power5
N931L828
N211J3021

So this tells me that the car code is on the driver board, and the power amp is the second board,which may indicate that simply swapping the power amp board will work, without running into car security code issues.

I saw nothing obvious on the 2 boards, but I have a feeling the problem is the audio is not getting to the power amp board.
BTW, the driver board has a blue connector that looks to be electrical audio in. I have asked HK for a schematic, and I'm waiting for a response from an intelligent human. And, I hope I can get the HK model number and maybe track down the schematic on their website

azureblue · Post by **azureblue** » 19 Jul 2023, 07:58

Progress so far:
I found a used unit, and I'm going to plug it in today. Dealer is telling me that some of those units can't be re- coded, some may work anyway, but it will cost non refundable $300 to code it.

azureblue · Post by **azureblue** » 19 Jul 2023, 16:41

the finale --

You can just swap amps - I found one from a 2013 s60 that did not have the same PN but the same # of output channels. No security codes involved, worked right away. Best $33 I ever spent..

JUST FYI, there are several models of the power amp, and conflicting lists of what fits what. the 2013 is held in by 3 10mm bolts, with the PITA one on the side of the unit. I had to unbolt the seat to get to it. On my 14, there are just 2 10's at the front, so moving the seat all the way back let's you unbolt, unhook, and remove through the front.

I'd love to find the differences between the models of the amp - I have a feeling that the upgrade levels are in the amp, not in the head unit..