Onkyo TX-SR608 HiFi Receiver

In order to challenge myself, and learn new repair skills I decided to try my hand at repairing this OnkyoTX-SR608 HiFi receiver to use at the heart of my home cinema. When it was released in 2010 it retailed at £500 and won a number of awards, including What HiFi Home Cinema amplifier product of the year (and 5 stars).

Onkyo TX-SR608 Home Cinema receiver

The eBay listing said that the left channel wasn’t working, which I thought might be a simple fix, and I would have lots of other channels to compare with for diagnostics. On arrival, the signs were good, original box with the manuals and remote control, and the unit itself was in mint condition.

I tested each channel by connecting up a Gale Gold bookshelf speaker to each channel and running the channel test, and quickly confirmed that the left channel was indeed dead.

Inside the receiver

With the top removed, the insides were clearly laid out, with the power supply shown on the right, and the input processing board at the bottom left. Behind that sits the pre-amp board and at the back a row of power transistors, attached to a sizable heatsink. All this is topped by a standard PC fan – I have read that these units suffer from overheating.

I decided to start with the pre-amplifier board to see what I could see – to cut a long inspection short – everything looked ok. The board is nicely designed with each channel clearly laid out in labelled columns.

Pre-amplifier board

I started taking the diode measurements of the preamp transistors and immediately noticed that one of them read differently when compared against all of the other channels. My initial assumption was that this transistor, or one of the surrounding components, had blown. Swapping the transistor was going to be a pain as it was inside a metal cage; I assume for heat dissipation. So before removing it I decided to test the surrounding components and to my surprise I quickly found a dead resistor (R5090).

Removing this, I was quickly able to confirm that what should have been a 100K resistor was dead.

Testing the suspect resistor

Replacing the resistor and retesting the readings around the transistor confirmed that they now matched the other channels. Putting it all back together, I retested all of the channels and – success – they all worked.

To be honest, I think I got quite lucky with this repair, although faults on this pre-amplifier board seem to be common due to the heat generated. Now to find some home cinema speakers to complete the system.