Add post: Marantz SR5200 Repair Log

content/posts/2016-01-21-marantz-sr5200-repair-log.md

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+date = "2016-01-21"
+title = "Marantz SR5200 Repair Log"
+tags = ["ohmexpress", "repair", "audiorepair"]
+description = "A Marantz SR5200 receiver with a non-working front-right channel. Let's fix that!"
+slug = "marantz-sr5200-repair-log"
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+
+I've been working on a Marantz SR5200 recently that came in with the front-right channel
+not outputting any sounds. Well, sounds like project!
+
+## Diagnostics
+
+First step is to see how the problem presents itself and under what circumstances. I've
+learned not to blindly rely on the symptoms a seller describes. When a seller states
+that the right speakers does not work, it really means it does not work with my current
+settings and setup.
+
+Again, let's first make visual inspection of the insides of the unit to make sure there
+are not already some obviously burned or damaged parts - all looked fine. Let's start
+with the head phones again to see if we get any output. Indeed, there's no sound on the
+right channel. Next, speakers, same issue.
+
+Now, I started playing with some buttons and testing different inputs. The issue did not 
+appear when:
+
+ 1. Using the direct 7.1 input
+ 2. 'Source Direct' was on
+ 3. When using the built-in tuner
+
+The first and second points were a big help for me. If 'Source Direct' is on, the whole 
+signal processing is bypassed, and the right channel works fine. This rules out the
+power-amp stage as the culprit and points the finger to the DSP board. 
+
+Tracing back the schematic from what are the L+R channel outputs of the DSP board, 
+I first encounter a IC725, a low noise opamp named [NJM2068M](https://octopart.com/njm2068m-new+japan+radio-419669).
+This opamp processes both analog L+R channels. Indeed, the left outputs and inputs measure
+ok, but the right channel is completely dead. On to the next IC.
+
+Next in line is IC720, the CS4391 24bit/192kHz DAC, which converts the digital signal
+to analog. All signal processing is digital on this device, so it makes sense for this
+IC to be by-passed in direct-mode.
+
+![Schematic Marantiz SR5200 / IC720](/img/marantz-sr5200-dac-schema-cs4391.png)
+
+Doing a quick search for the CS4391 and Marantz it becomes clear this IC is 
+a common cause of trouble. 
+
+To be sure I checked the analog input signal for the L+R channels as well. They end 
+up in IC719. This IC does several things, but most importantly it has two ADCs to 
+convert L+R channels to digital, and it features six DACs which are used for
+center, surround and subwoofer channels. Since the analog singal is coming in ok and
+the right surround channel is also working fine, I'm inclined to assume the
+digital processing of the right channel is also fine. 
+
+![Schematic Marantiz SR5200 / IC719](/img/marantz-sr5200-dac-schema-cs4228.png)
+
+This in combination with the bad reputation the CS4391 has, I decided to replace the
+L+R channel DAC. 
+
+## The Repair
+
+A replacement was quickly ordered and the TSSOP-20 IC replaced.
+Here's the original IC (IC720) on the DAC board:
+
+![Schematic Marantiz SR5200 / IC720-original](/img/marantz-sr5200-dac-original.jpg)
+
+The replacement is really easy, don't let the small size scare you. All you need is a 
+soldering iron, ESD tweezers, solder wick and a flux pen.
+
+First removal. With a bevel point heat up one row of the IC's pins. Heat
+them up equally. Use the tweezers to left the IC off the PCB, repeat on the other
+side and the IC is gone. 
+
+Next, you might want to use the solider wick to remove any exces solder left on the
+pads. Be careful not to damage the pads, though. 
+
+Putting in the new IC is also not as hard as you might think. 
+
+Apply flux liberally on one row of pads, don't be scared to touch the IC. Feed a 
+little solder onto the tip of your soldering iron. With one hand use the tweezers 
+to place the IC (make sure of the orientation!) and use the other to drag the 
+soldering iron neatly across the pins. The applied flux will clean the
+pads and pins and make the solder flow properly. 
+
+If you did not add too much solder, the result should be neatly soldered pins. If not,
+use your solder wick to remove exces solder, optionall re-apply some flux and
+drag again until you get it right. It might help to have a (10x) magnifying glass
+at hand to inspect your handy work. 
+
+This is the end result:
+
+![Schematic Marantiz SR5200 / IC720-replacement](/img/marantz-sr5200-dac-replaced.jpg)
+
+As you can see the flux leaves behind quite a mess, but it's (electrically) harmless stuff,
+it just looks ugly. I really should be some flux cleaner.
+
+With this done, I reassembled the SR5200 receiver and voilà, nice sounding music from all
+channels as you'd expect!
+
+## Next steps
+
+![Schematic Marantiz SR5200 / IC720-replacement](/img/marantz-sr5200-front.jpg)
+
+During testing I noticed the volume knob not registering every step, e.g. the volume 
+would not be adjusted according to how I turn the knob. This is due to the rotary encoder
+(often erroneously called poteniometer) having some dirty contacts. I've orderd some
+Kontact 60 to resolve this - and update and photos on that later. 
+