EEVBlog #379 - Yamaha RX-V557 Receiver Fix

• EEVBlog #379 - Yamaha RX-V557 Receiver Fix
  Posted by EEVblog on 31 Oct, 2012 03:27
• 
  
  Dave.
• #1 Reply
  Posted by NiHaoMike on 31 Oct, 2012 04:42
• Is there a patent on that circuit? If so, reading it would be the best way to understand how it works.
  
  Maybe saw that bad cap in half to see how it might have failed. It looks like the manufacturing is defective and one of the terminals detaches internally.
• #2 Reply
  Posted by Pentium100 on 31 Oct, 2012 05:00
• I was fixing a dehumidifier that would cycle its power for some time until it warmed up and worked normally when I encountered a bad film cap for the first time. The 1uF cap had either reduced capacity or increased ESR, but the result was that when the MCU switched on the relay (for the compressor), the voltage would dip and the MCU would reset. The capacitor was used in a CR dropper to provide 5V without the use of a transformer.
• #3 Reply
  Posted by firewalker on 31 Oct, 2012 07:31
• OFF TOPIC.
  
  Can someone put an LCR to an oscilloscope an post the waveform? Is it sine?
  
  Alexander.
• #4 Reply
  Posted by David_AVD on 31 Oct, 2012 07:35
• Quote from: Pentium100 on 31 Oct, 2012 05:00

  The capacitor was used in a CR dropper to provide 5V without the use of a transformer.

  
  There's quite a bit of gear that uses a capacitor fed supply like that.  Pump controllers, vacuum cleaners, etc.  It's also the first thing to check (for low capacitance) when servicing these items.  They usually drop capacitance slowly until the circuit no longer operated correctly.
• #5 Reply
  Posted by nitro2k01 on 31 Oct, 2012 11:44
• Hmmm, 5.5 V from regulator minus nominal 0.7 V diode = ~4.8 V?
  
  8:24, no that's actually a Zener that you're pointing at. It's a 10V Zener that's clamping the voltage for the half cycle when a positive voltage is presented over the didoe. Then that is filtered through D406 and C406 which then goes to Vdd for the rest of the circuit.
  
  A Zener will typically have the brackets pointing counter clockwise, like a Z, whereas a Schottky will typically have them pointed clockwise like an S, and also have another little line segment.
  
  
  Oh and btw...
  
• #6 Reply
  Posted by Sionyn on 31 Oct, 2012 12:51
• ah come on dave ACDC would've been better
• #7 Reply
  Posted by Rutger on 31 Oct, 2012 14:48
• No way Man at Work it 10x times better, I love that band from Down Under.
• #8 Reply
  Posted by Skippy on 31 Oct, 2012 15:36
• Where did you get the schematic from (did you say during the video?)
• #9 Reply
  Posted by Sionyn on 31 Oct, 2012 15:42
• id like to see dave do a angus young
  
  
• #10 Reply
  Posted by Rutger on 31 Oct, 2012 19:10
• Wondering were this was filmed? Looks very dry, but you have a power lines in the background.
• #11 Reply
  Posted by Baliszoft on 31 Oct, 2012 19:19
• How about this?
  Family Guy land Down Under
• #12 Reply
  Posted by Dread on 31 Oct, 2012 20:28
• Doing repair work for years I know how Dave feels when people point out "Ohh it's that part that’s bad". I had a guy in our company that seemed to have a photographic memory when it came to remembering boards he had been through already and he did that all the time.
  
  My only comment to Dave would be that he broke one of the main rules of Repair and therefore paid the price.
  "Never Ignore a voltage reading that is unexpected, always back track the problem and fix it first!"
  Had Dave not ignored those oscillating reading after the bridge Rectifier and just stepped back to see where they came from he would have seen the problem in less than 10 minutes.  Of course that's easy for me to say when working at a bench with no camera rolling so in a way I do understand why he moved on to other areas.
  
• #13 Reply
  Posted by PA0PBZ on 31 Oct, 2012 20:37
• Quote from: Dread on 31 Oct, 2012 20:28

  Had Dave not ignored those oscillating reading after the bridge Rectifier and just stepped back to see where they came from he would have seen the problem in less than 10 minutes.  Of course that's easy for me to say when working at a bench with no camera rolling so in a way I do understand why he moved on to other areas.
  

  
  Those readings are supposed to be that way, I think you missed what the circuit does.
• #14 Reply
  Posted by zaoka on 31 Oct, 2012 21:21
• DAVE Please!
  
  Dont? stop now when its most interesting!!
  
  I think that 10.2V on secundary is droping down at the moment you turn on the receiver.
  
  Please install old cap back and use MinMax(Peak) feature on Fluke and monitor 10.2V to see if it changes when you press power button.
  
  Its either going low or going high and IC403 (overvoltage protection) kicks in.
  
  Also measure the voltage across C406 at the moment you press power button.
  
  This is great opportunity to use scope on secundary to see how low and how long voltage going down at the moment you? turn the unit on and than use MinMax feature of Agilent, Fluke and GM meter to see if they all can catch that!
  
  Also we all have Fluke meters and would like to see more GM meter or Agilent in action
  
  Please dont give up now!! )
• #15 Reply
  Posted by Monkeh on 31 Oct, 2012 21:33
• Quote from: zaoka on 31 Oct, 2012 21:21

  Also we all have Fluke meters and would like to see more GM meter or Agilent in action
  

  
   
• #16 Reply
  Posted by Pentium100 on 31 Oct, 2012 21:48
• The secondary voltage may be OK, but most likely what happened was that the voltage for the 4013 chip was too low (it is supposed to be around 8V, but the chip can work down to 5V or a bit less IIRC), IC401 remained off (because it has 6.8V zener in series), PDET (power detect) signal remained low so the MCU went into protection mode and did not turn on.
  
  Interesting thing here is that the 5V regulator is on a different board. This standby power supply supplied 10.3V to it and gets back 5V.
• #17 Reply
  Posted by LEECH666 on 31 Oct, 2012 23:37
• Quote from: nitro2k01 on 31 Oct, 2012 11:44

  Hmmm, 5.5 V from regulator minus nominal 0.7 V diode = ~4.8 V?
  
  8:24, no that's actually a Zener that you're pointing at. It's a 10V Zener that's clamping the voltage for the half cycle when a positive voltage is presented over the didoe. Then that is filtered through D406 and C406 which then goes to Vdd for the rest of the circuit.
  
  A Zener will typically have the brackets pointing counter clockwise, like a Z, whereas a Schottky will typically have them pointed clockwise like an S, and also have another little line segment.
  
  
  Oh and btw...
  
  

  
  Trollcap strikes again. Made me chuckle. xD
• #18 Reply
  Posted by LaurenceW on 01 Nov, 2012 19:16
• Dave, is that the only sound you can get out of the Yammy? If so, I fear she's still skewered, mate.  Can you check if you've accidentally pressed any "Lo_Quality" button on the front?
• #19 Reply
  Posted by EEVblog on 01 Nov, 2012 23:52
• Quote from: LaurenceW on 01 Nov, 2012 19:16

  Dave, is that the only sound you can get out of the Yammy? If so, I fear she's still skewered, mate.  Can you check if you've accidentally pressed any "Lo_Quality" button on the front?
  

  
  Assuming that wasn't sarcasm 
  The lapel mic was very close to the woofer, so you'd get huge low end domination from that placement, giving it that "low-fi" effect.
  It sounds just fine in real life.
  
  Dave.
• #20 Reply
  Posted by poptones on 02 Nov, 2012 06:28
• As good as men at work can sound I suppose. Seems to me you went an awful long way to such a short destination.
  
  I can definitely count an aussie among my favorites, but she's aged a lot better than the blokes.
  
  
  
  
  
  
  
  
  
  
  
• #21 Reply
  Posted by Salas on 03 Nov, 2012 20:55
• Nick Cave is an Aussie performer/songwriter who has some musical depth and deserves to be mentioned also, although Minogue has a certain "back"ground. They had done Where The Wild Roses Grow duet though which was a spooky but fine antipodean coalition IMO. She is just 43 or 44, the Men At Work blokes must be in their 60s now. The frontman was Scottish BTW although he had turned Vegemite to the bone after he had moved to Australia.
• #22 Reply
  Posted by poptones on 03 Nov, 2012 22:24
• I didn't know nick cave was aussie, I thought he was part of that london scene. Interesting.
  
  Another of my favorites was Midnight Oil. I had at least three of their albums, I used to like listening to Red Sails in the Sunset because it had "Kosciusko" on it and I lived near Kosciusko (MS, not oz).
• #23 Reply
  Posted by Salas on 03 Nov, 2012 23:15
• Yeah, Cave had this divided Berlin squatter wasted outlook and that Blixa mate from Einstürzende Neubauten, so he could be easily passed for underground European roots, or as Londoner bcs he formed The Bad Seeds there, but he is very much an Aussie, his first moderately known outside Oz band The Birthday Party was formed in Australia.  The Oils's vocalist turned to a politician. INXS was another Oz world export, and the super rich and famous Mancunian Bee Gees started their music making as relocated kids in Australia, made hits and returned to England to push their career, as they actually succeeded. 
• #24 Reply
  Posted by poptones on 03 Nov, 2012 23:20
• Oil's vocalist turned to a politician? You mean someone would vote for a guy who likes like the bad guy from "The Hills Have Eyes?"