DC Offsets on output - protection don't allowd to switch on
Yamaha RX-V765 Amplifier - DC Offset problem. - The amplifier is few month old and it was working well. - Now protection switch off the amplifier during booting process - in moment when speakers' relay need to be switched on. - The amplifier is possible to switch on with bypassing protection (I have Service Manual) and in this state the amplifier is working. - Checking the history of faults inside service menu shows DC Offset problems. - Measuring on the speakers shows different DC offsets on all channels (-0.250 V, +0.160 V, -1.270 V, +1.650 V,....). All supply voltage inside the amplifier are OK. It is very strange how DC Offsets on output of all 7 channels are to high without any serious damage. Any suggestion how to solve this problem? (Unfortunatelly I am not in position to use warranty because in my country doesn't exist Yamaha Service Center and I need to repair it myself). Thanks
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Re: DC Offsets on output - protection don't allowd to...
You don't want to do this( bypass the protection0
that d.c. output will burn the coils in your speakers with out making a sound!! you have a biasing problem
or like you said a d.c. offset problem it is best to work on this problem with out a load on the amp, this will allow you to trace back where the trouble is starting at. caps will cause this sort of problem but leaky transistors can also do this, even diodes.
this will require an experienced trouble-shooter.
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I would also guess you have a flashing indicator, correct? If you do, your amplifier has DC Offset(a damaged amplifier). If this is the case, the protection circuit will not allow audio on any channel.
If you are interested in having your Yamaha repaired, please look at my website, audioserviceclinic.com. You may contact me there. Thank you.
Your amp is probably in Protect Mode, meaning you have DC Offset( a damaged amplifier). That will have to be repaired, before you can switch the unit on. If you need more assistance, or would like to inquire about repairing it, please visit my website at audioserviceclinic.com. You may contact me there. Thank you.
THIS IS "DC OFFSET". MOST AMPLIFIER PROTECTION CIRCUITS REACT TO THIS CONDITION BY SHUTTING THE AMPLIFIER DOWN. THIS IS A CONDITION, NORMALLY BROUGHT ON BY SHORTED OUTPUT TRANSISTORS, THAT ARE TRYING TO PASS THE POWER SUPPLY DC CURRENT TO THE SPEAKERS, WHICH IN A MATTER OF SECONDS, WOULD BURN THE VOICE-COILS IN THE SPEAKERS. MOST TIMES THIS WOULD BE CHARACTERIZED AS HOOKING THE SPEAKERS UP AND OBSERVING THEM SIMPLY POKING OUT OR IN CONSTANTLY WHICH CREATES MUCH EXCESS HEAT. THIS IS WHY THE AMPLIFIER WILL SHUT DOWN TO PROTECT THE SPEAKERS. YOU CAN TRY TO DISCONNECT THE SPEAKERS AND THE RCA INPUTS THEN POWER THE AMPLIFIER UP. IF THE DC OFFSET LIGHT STILL ILLUMINATES, THEN YOU WILL HAVE TO HAVE THIS UNIT REPAIRED. ONCE REPAIRED, BEFORE REINSTALLING IT, MAKE SURE TO CHECK YOUR SPEAKERS FOR DAMAGED VOICE-COILS, WHICH COULD HAVE BEEN THE PRIMARY CAUSE OF FAILURE. OK. LET ME KNOW IF YOU NEED FURTHER ASSISTANCE....V
Hi friend,when something goes wrong in the output of the amplifier the protection circuit take place to prevent further damage could cause by DC power such as speakers or other related circuits...I think in your situation either one or both output amp stage have blown,then the protection cct turned on (not blown protection circuit!?). If so you have to check all the output transistors for short cct, if shorted you must also check all the DC bias cct nearby such as small transistors,resistors...If you are not familar with amplifier it better to find a tech as all amplifiers need a very precide repair technic , If the DC BIAS were wrong , when you turn on the power it will blow straight away! All times and cost will be waisted!
Ahhh, the good ole Bose 901. (I like those)... And you want to connect them to the Yamaha RX-V765 AV receiver. That should be a piece of cake. I assume you only have two Bose 901 cabinets. If so, you simply need to connect one end of your speaker wires to the terminals found on the 901 cabinets, and the other end of the speaker wires need to go to the Front Left and Front Right speaker outputs of the RX-V765. The RX-V765 is a 7 channel surround receiver. Weather you run it as a 7 channel theatre or as a more classic 2 speaker configuration, you will want to run the 901 cabs from the Front L and Front R speaker outputs, unless for some reason you want to specifically use them for any of the surround channels in which case it will not harm anything if you use them for surrounds - it's just that if you're simply wanting to use them as your principal speakers, you want Front L and Front R.
So connect them as I explained, power the receiver up, put on your favorite CD and enjoy!
Firstly, check for conductive hold down glue about the output stages. This can cause the problem you have. Or there may be a failing component somewhere in the output stage of that channel. Check for leaky transistors,diodes an capacitors. You will need to remove semiconductors to check for leakage, If you dont have alot of experience faultfinding amplifier power stages, I suggest you take it to a NAD authorised service center.