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Glurp
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Topic # 193687 20-Mar-2016 16:32
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My RX V-750 has served me faithfully for years. It is still a good amp and I love it and I could not afford to replace it with anything of equivalent quality anyway.

 

The problem is that recently it has started intermittently failing to come on. When it doesn't want to start, nothing seems to make a difference. Replugging, hammering the standby button, anything I try it just sits there dead to the world. Nothing at all happens, no light, no error, no click of the relay. 

 

Yet if I let it sit overnight, it starts normally. At least it has so far. All of this makes me think excess heat and failing capacitors, but there is another variable. I have been working on automating my streaming computer and have programmed a lot of different codes into my Harmony remote. A couple of times the amp has stopped working when I was testing those codes. Hence my question: Is there any kind of diagnostic or technical IR code that anyone knows of that could put the amp to sleep? I'm not talking about the normal power off toggle, but something that sends it into a coma. I'm just trying to narrow down the possibilities before I go to the considerable trouble of disconnecting everything and taking it to a repair shop. I don't want to pay a technician to tell me there is nothing wrong with it. I need to be as sure as I can that the IR codes I am playing with cannot be affecting it in any way.

 

 

 

 





I reject your reality and substitute my own. - Adam Savage
 


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  Reply # 1516467 20-Mar-2016 16:41
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Defiantly can crash devices with wrong IR codes. I had a mis-learned code in my remote ones that would have a decent chance of crashing my veon tv.





Richard rich.ms

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  Reply # 1516468 20-Mar-2016 16:42
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I'd contact the distributor who have a reasonable support crew. Sound Group Holdings. If it's faulty they may be able to repair it. There are a few second hand similar amp's on TM if your budget doesn't stretch to a new one.


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  Reply # 1516583 20-Mar-2016 18:58
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What part of the country are you in? If you're in Auckland I'd second taking it to SGH.




Glurp
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  Reply # 1516621 20-Mar-2016 21:03
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No luck. I'm in Hastings.

 

 





I reject your reality and substitute my own. - Adam Savage
 


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  Reply # 1516666 20-Mar-2016 22:25
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Will have to check at work tomorrow, but fairly sure that is one of the models that suffer from a Mylar capacitor in the standby power supply that fails. A .022uf 630v from memory...
Will let you know.



Glurp
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  Reply # 1516699 21-Mar-2016 08:35
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Fantastic. Thanks heaps for that.

 

 





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  Reply # 1516717 21-Mar-2016 09:28
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That sounds about right, should be a simple fix if it is just the standby supply being intermittent.

 

Had a look at the schematic and it's a pretty simple arrangement, but interesting that it has a circuit powered via that capacitor to zero crossing pulse the standby transformer just enough to keep the standby supply high enough.. good power saving measure.

 

A couple of small electrolytics in the supply to that circuit and around the CPU board regulator which would be good to replace, I would've thought that .22uF would just totally fail giving no operation at all but I guess it could have gone low capacitance making things marginal, its series resistor would be worth checking too.

 

 




Glurp
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  Reply # 1516754 21-Mar-2016 11:05
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Any chance of getting a copy of that schematic or a link to it?

 

 





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  Reply # 1516859 21-Mar-2016 12:51
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Hi.

 

Had a look at work, and we don't have a copy of the circuit diagram for a Rx-V750. How ever 99% sure it is the same as the other model Yamaha amps of that age that all give this trouble. It is in the power saving circuit that the standby supply uses. Look for a brown 0.022uf 630v capacitor on the standby board. We use radio spares 476-4247 capacitors as the replacement.

 

Good luck.


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  Reply # 1516864 21-Mar-2016 12:52
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Will be marked 223K on capacitor.

 

 




Glurp
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  Reply # 1516903 21-Mar-2016 13:35
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Ok thanks very much for that. At the moment it seems to be working again. I think I will wait until it dies completely or becomes unacceptably unreliable before opening it up. Just disconnecting it and labelling all the cables will take half a day.

 

 





I reject your reality and substitute my own. - Adam Savage
 


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  Reply # 1516904 21-Mar-2016 13:36
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I have a Yamaha RX V1400 that had the same issue a 3-4 years ago - took it to SGH - excellent service, and fairly priced.

 

Same issue - not turning on - got worse and worse until it eventually wouldn't turn on at all. The tech mentioned it was a common issue, and also replace a couple of other components. And yes, was a mission to untangle it from it's umbilical cords frown.  But has been reliable ever since.

 

 





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