Recently, I’ve managed to sucessfully repair my Marantz SR5200 receiver (surround sound amplifier). This is a quick note as an internet record to say what to do if you have similar problems.
First of all the symptoms:
The main symptom is intermittent (at least in my case) loud hissing / static / white noise on more than one speaker, which you can reduce the level of with the volume control.
I did a bit more investigation:
- It only happens on the front 2 speakers, not any of the others (i.e. not centre or surround)
- It doesn’t affect the radio / tuner
- It affects all the other inputs regardless.
- It goes away if you use source direct on an analogue input (but not a digital one).
- It doesn’t happen if you put the signal straight into the pre-amp (i.e. 7-channel input mode)
There is a service manual that you can download for free as a multipart rar file if you find the right place. The block diagram in that clearly identifies one component as the culprit – the stereo DAC (a CS4391, IC720) on the DSP board. If you look at the detailed schematics there are actually quite a few other components in that path, however it was the DAC 🙂
So the good news is that you can still get the part without too much trouble. I used a CS4391A which is a suitable alternative (technically it can only work with the analogue at 5V as opposed to a wider range, however the analogue input is at 5V). The bad news is that it isn’t really a DIY repair. It is a surface mount component and requires either considerable skill with a soldering iron or the use of hot air to melt the solder. Fortunately for me the latter was available at work, along with someone skilled at using it. If you find another amp with a different fault (e.g. not working on one channel only) then taking the DSP board out of that one is relatively easy (but you will need to take the back panel off to get the DSP board out) and suitable for DIY.
This issue appears to be relatively common (looking at eBay for a faulty one usually returned one with the same fault), and I dare say may affect the Marantz SR6200 as well (same service manual). Interestingly I had always thought that I couldn’t hear a difference when playing CDs between using a digital lead from the DVD player and an analogue one. Not suprising seeing that they use the same DAC!
I hope this might help someone else.