Yamaha RX-V750

[Canixys]

Hi!

I´m looking for a service manual for a Yamaha RX-V750, but in case no one has it, I may try to get some help here.

I don´t have any sound out, I believe it has something to do with the relay circuit beacuse I can only hear 2 relay clicks. The first click is from the PSU but the second click is a little harder to hear from wich relay the sound comes from.

I have tryed to factory reset the unit but with no luck. And I don´t think it is the power mosfet´s in audio circuit. How much voltage is it across the relay coil´s on a working RX-V750!?

Excuse my english and grammar

best regards
Canixys

[Guest]

Hey there will try to help, The second click usually states that the post (Power on self test) has passed and the audio signal is sent to the outputs, But first you must check that none of your speaker are shorted unplug all speakers and turn the unit on and see if it goes into failsafe mode. If not then speakers or speaker in speakers are bad. If it does the the second click you hear is failsafe, the unit is turning itself off.
Here is a way to determine if a section of the unit is bad. Take off the cover and check the Impeadance on the bias resistors they are usually large white three pin resistors they should have what resistance is shown on them the outer pins. Also unplug each stage from its B+ source starting with the fronts just unplug the connector and turn it on and see if it stays on, IF not then you have a shorted output or open bias resistor also if the bias resistor are open, it should show continuity on all pins, then you can be almost sure that output associated with it is leaky or bad.

As i stated unplug each stage first fronts then center,rears, and also a bad bass woffers can cause failsafe, make sure you unplug one stage at a time and plug the previous section back up or the unit will go into failsafe think something is wrong because it does not sense B+

Hope this helps turn the unit on each time you unplug a section of the outputs and then you can determine which ares is faulty..

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[Canixys]

Hi techmen007!


I will check it up later this day. Yesterday I took the cover off and looked around and I decided to take a look under the boards just in case there would be any bad soldering. When I came to the outgoing audio signal board I found a crack that crossed several leads. Yes this must be it I thought, so I plugged in my solderstation and begun to solder wires over the broken leads.

When I was finish I turned the unit on, and now I can just hear one click from the power supply. but now I have sound out from the headphone plug. (I didn´t have this before). So I will take a closer look today at the board again and I will try your suggestion too.

Canixys

[Canixys]

Hi!

Today I´m happy beacuse I have found why the relay´s didn´t work properly. It was a tiny crack on the voltage rail to all relay´s. So now it works like a charm. Tuned in a local radio station and the sounds pumps out of all speaker connection

Regards

Canixys